Cosmic ray

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Cosmic flux versus particle energy Cosmic ray flux versus particle energy.svg
Cosmic flux versus particle energy

Cosmic rays are high-energy radiation, mainly originating outside the Solar System [1] and even from distant galaxies. [2] Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed primarily of high-energy protons and atomic nuclei, they are originated either from the sun or from outside of our solar system. Data from the Fermi Space Telescope (2013) [3] have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernova explosions of stars. [4] Active galactic nuclei also appear to produce cosmic rays, based on observations of neutrinos and gamma rays from blazar TXS 0506+056 in 2018. [5] [6]

Ionizing radiation radiation that carries enough energy to liberate electrons from atoms or molecules

Ionizing radiation is radiation that carries enough energy to detach electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic subatomic particles, ions or atoms moving at high speeds, and electromagnetic waves on the high-energy end of the electromagnetic spectrum.

Solar System planetary system of the Sun

The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.

Atmosphere of Earth Layer of gases surrounding the planet Earth

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention, and reducing temperature extremes between day and night.

Contents

Etymology

The term ray is somewhat of a misnomer due to a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In common scientific usage, [7] high-energy particles with intrinsic mass are known as "cosmic" rays, while photons, which are quanta of electromagnetic radiation (and so have no intrinsic mass) are known by their common names, such as gamma rays or X-rays , depending on their photon energy.

Electromagnetic radiation form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space

In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.

Gamma ray electromagnetic radiation of high frequency and therefore high energy

A gamma ray or gamma radiation, is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; he had previously discovered two less penetrating types of decay radiation, which he named alpha rays and beta rays in ascending order of penetrating power.

X-ray form of electromagnetic radiation

X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, who usually is credited as its discoverer, and who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray(s) in the English language includes the variants x-ray(s), xray(s), and X ray(s).

Massive cosmic rays compared to photons

In current usage, the term cosmic ray almost exclusively refers to massive particles – those that have rest mass – as opposed to photons, which have no rest mass, and neutrinos, which have negligible rest mass. Massive particles have additional, kinetic, mass-energy when they are moving, due to relativistic effects. Through this process, some particles acquire tremendously high mass-energies. These are significantly higher than the photon energy of even the highest-energy photons detected to date. The energy of the massless photon depends solely on frequency, not speed, as photons always travel at the same speed. At the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays.

The term massive particle refers to particles which have real non-zero rest mass. According to special relativity, their velocity is always lower than the speed of light. The synonyms bradyon, tardyon or ittyon are sometimes used to contrast with luxon and hypothetical tachyon.

The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force. The photon has zero rest mass and always moves at the speed of light within a vacuum.

Neutrino Elementary particle with very low mass that interacts only via the weak force and gravity

A neutrino is a fermion that interacts only via the weak subatomic force and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The mass of the neutrino is much smaller than that of the other known elementary particles. The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos, as leptons, do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.

The highest-energy fermionic cosmic rays detected to date, such as the Oh-My-God particle, had an energy of about 3×1020  eV , while the highest-energy gamma rays to be observed, very-high-energy gamma rays, are photons with energies of up to 1014 eV, and the highest energy neutrinos detected so far have energies of several 1015 eV. Hence, the highest-energy detected fermionic cosmic rays are about 3×106 times as energetic as the highest-energy detected cosmic photons.

Fermion quantum system whose wave function changes when exchanging identical instances

In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. These particles obey the Pauli exclusion principle. Fermions include all quarks and leptons, as well as all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions differ from bosons, which obey Bose–Einstein statistics.

The Oh-My-God particle was the highest-energy cosmic ray detected so far (as of 2019), by the Fly's Eye detector in Dugway Proving Ground, Utah, US, on 15 October 1991. Its energy was estimated as (3.2±0.9)×1020 eV, or 51 J. This is 20 million times more energetic than the highest energy measured in electromagnetic radiation emitted by an extragalactic object and 1020 (100 quintillion) times the photon energy of visible light, equivalent to a 142-gram (5 oz) baseball travelling at about 26 m/s (94 km/h; 58 mph).

In physics, the electronvolt is a unit of energy equal to approximately 1.6×10−19 joules in SI units.

Composition

Of primary cosmic rays, which originate outside of Earth's atmosphere, about 99% are the nuclei of well-known atoms (stripped of their electron shells), and about 1% are solitary electrons (similar to beta particles). Of the nuclei, about 90% are simple protons (i.e., hydrogen nuclei); 9% are alpha particles, identical to helium nuclei; and 1% are the nuclei of heavier elements, called HZE ions. [8] These fractions vary highly over the energy range of cosmic rays. [9] A very small fraction are stable particles of antimatter, such as positrons or antiprotons. The precise nature of this remaining fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them.[ citation needed ]

Beta particle ionizing radiation

A beta particle, also called beta ray or beta radiation, is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β decay and β+ decay, which produce electrons and positrons respectively.

Proton nucleon (constituent of the nucleus of the atom) that has positive electric charge; symbol p

A proton is a subatomic particle, symbol
p
or
p+
, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons".

Alpha particle helium-4 nucleus; a particles consisting of two protons and two neutrons bound together

Alpha particles, also called alpha ray or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are also sometimes written as He2+
or 4
2
He2+
indicating a helium ion with a +2 charge. If the ion gains electrons from its environment, the alpha particle becomes a normal helium atom 4
2
He
.

Energy

Cosmic rays attract great interest practically, due to the damage they inflict on microelectronics and life outside the protection of an atmosphere and magnetic field, and scientifically, because the energies of the most energetic ultra-high-energy cosmic rays (UHECRs) have been observed to approach 3 × 1020 eV, [10] about 40 million times the energy of particles accelerated by the Large Hadron Collider. [11] One can show that such enormous energies might be achieved by means of the centrifugal mechanism of acceleration in active galactic nuclei. At 50 J, [12] the highest-energy ultra-high-energy cosmic rays have energies comparable to the kinetic energy of a 90-kilometre-per-hour (56 mph) baseball. As a result of these discoveries, there has been interest in investigating cosmic rays of even greater energies. [13] Most cosmic rays, however, do not have such extreme energies; the energy distribution of cosmic rays peaks on 0.3 gigaelectronvolts (4.8×10−11 J). [14]

In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles.

Large Hadron Collider particle collider

The Large Hadron Collider (LHC) is the world's largest and most powerful particle collider and the largest machine in the world. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories, as well as more than 100 countries. It lies in a tunnel 27 kilometres (17 mi) in circumference and as deep as 175 metres (574 ft) beneath the France–Switzerland border near Geneva.

Centrifugal acceleration of astroparticles to relativistic energies might take place in rotating astrophysical objects. It is strongly believed that active galactic nuclei and pulsars have rotating magnetospheres, therefore, they potentially can drive charged particles to high and ultra-high energies. It is a proposed explanation for ultra-high-energy cosmic rays (UHECRs) and extreme-energy cosmic rays (EECRs) exceeding the Greisen–Zatsepin–Kuzmin limit

History

After the discovery of radioactivity by Henri Becquerel in 1896, it was generally believed that atmospheric electricity, ionization of the air, was caused only by radiation from radioactive elements in the ground or the radioactive gases or isotopes of radon they produce. [15] Measurements of increasing ionization rates at increasing heights above the ground during the decade from 1900 to 1910 could be explained as due to absorption of the ionizing radiation by the intervening air. [16]

Discovery

In 1909, Theodor Wulf developed an electrometer, a device to measure the rate of ion production inside a hermetically sealed container, and used it to show higher levels of radiation at the top of the Eiffel Tower than at its base. However, his paper published in Physikalische Zeitschrift was not widely accepted. In 1911, Domenico Pacini observed simultaneous variations of the rate of ionization over a lake, over the sea, and at a depth of 3 metres from the surface. Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth. [17]

Pacini makes a measurement in 1910. Pacini measurement.jpg
Pacini makes a measurement in 1910.

In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers [18] to an altitude of 5,300 metres in a free balloon flight. He found the ionization rate increased approximately fourfold over the rate at ground level. [18] Hess ruled out the Sun as the radiation's source by making a balloon ascent during a near-total eclipse. With the moon blocking much of the Sun's visible radiation, Hess still measured rising radiation at rising altitudes. [18] He concluded that "The results of the observations seem most likely to be explained by the assumption that radiation of very high penetrating power enters from above into our atmosphere." [19] In 1913–1914, Werner Kolhörster confirmed Victor Hess's earlier results by measuring the increased ionization enthalpy rate at an altitude of 9 km.

Increase of ionization with altitude as measured by Hess in 1912 (left) and by Kolhorster (right) HessKol.jpg
Increase of ionization with altitude as measured by Hess in 1912 (left) and by Kolhörster (right)

Hess received the Nobel Prize in Physics in 1936 for his discovery. [20] [21]

The Hess balloon flight took place on 7 August 1912. By sheer coincidence, exactly 100 years later on 7 August 2012, the Mars Science Laboratory rover used its Radiation Assessment Detector (RAD) instrument to begin measuring the radiation levels on another planet for the first time. On 31 May 2013, NASA scientists reported that a possible manned mission to Mars may involve a greater radiation risk than previously believed, based on the amount of energetic particle radiation detected by the RAD on the Mars Science Laboratory while traveling from the Earth to Mars in 2011–2012. [22] [23] [24]

Hess lands after his balloon flight in 1912. Hessballon.jpg
Hess lands after his balloon flight in 1912.

Identification

Bruno Rossi wrote that:

In the late 1920s and early 1930s the technique of self-recording electroscopes carried by balloons into the highest layers of the atmosphere or sunk to great depths under water was brought to an unprecedented degree of perfection by the German physicist Erich Regener and his group. To these scientists we owe some of the most accurate measurements ever made of cosmic-ray ionization as a function of altitude and depth. [25]

Ernest Rutherford stated in 1931 that "thanks to the fine experiments of Professor Millikan and the even more far-reaching experiments of Professor Regener, we have now got for the first time, a curve of absorption of these radiations in water which we may safely rely upon". [26]

In the 1920s, the term cosmic rays was coined by Robert Millikan who made measurements of ionization due to cosmic rays from deep under water to high altitudes and around the globe. Millikan believed that his measurements proved that the primary cosmic rays were gamma rays; i.e., energetic photons. And he proposed a theory that they were produced in interstellar space as by-products of the fusion of hydrogen atoms into the heavier elements, and that secondary electrons were produced in the atmosphere by Compton scattering of gamma rays. But then, sailing from Java to the Netherlands in 1927, Jacob Clay found evidence, [27] later confirmed in many experiments, of a variation of cosmic ray intensity with latitude, which indicated that the primary cosmic rays are deflected by the geomagnetic field and must therefore be charged particles, not photons. In 1929, Bothe and Kolhörster discovered charged cosmic-ray particles that could penetrate 4.1 cm of gold. [28] Charged particles of such high energy could not possibly be produced by photons from Millikan's proposed interstellar fusion process.[ citation needed ]

In 1930, Bruno Rossi predicted a difference between the intensities of cosmic rays arriving from the east and the west that depends upon the charge of the primary particles—the so-called "east-west effect." [29] Three independent experiments [30] [31] [32] found that the intensity is, in fact, greater from the west, proving that most primaries are positive. During the years from 1930 to 1945, a wide variety of investigations confirmed that the primary cosmic rays are mostly protons, and the secondary radiation produced in the atmosphere is primarily electrons, photons and muons. In 1948, observations with nuclear emulsions carried by balloons to near the top of the atmosphere showed that approximately 10% of the primaries are helium nuclei (alpha particles) and 1% are heavier nuclei of the elements such as carbon, iron, and lead. [33] [34]

During a test of his equipment for measuring the east-west effect, Rossi observed that the rate of near-simultaneous discharges of two widely separated Geiger counters was larger than the expected accidental rate. In his report on the experiment, Rossi wrote "... it seems that once in a while the recording equipment is struck by very extensive showers of particles, which causes coincidences between the counters, even placed at large distances from one another." [35] In 1937 Pierre Auger, unaware of Rossi's earlier report, detected the same phenomenon and investigated it in some detail. He concluded that high-energy primary cosmic-ray particles interact with air nuclei high in the atmosphere, initiating a cascade of secondary interactions that ultimately yield a shower of electrons, and photons that reach ground level. [36]

Soviet physicist Sergey Vernov was the first to use radiosondes to perform cosmic ray readings with an instrument carried to high altitude by a balloon. On 1 April 1935, he took measurements at heights up to 13.6 kilometres using a pair of Geiger counters in an anti-coincidence circuit to avoid counting secondary ray showers. [37] [38]

Homi J. Bhabha derived an expression for the probability of scattering positrons by electrons, a process now known as Bhabha scattering. His classic paper, jointly with Walter Heitler, published in 1937 described how primary cosmic rays from space interact with the upper atmosphere to produce particles observed at the ground level. Bhabha and Heitler explained the cosmic ray shower formation by the cascade production of gamma rays and positive and negative electron pairs. [39] [ citation needed ] [40]

Energy distribution

Measurements of the energy and arrival directions of the ultra-high-energy primary cosmic rays by the techniques of density sampling and fast timing of extensive air showers were first carried out in 1954 by members of the Rossi Cosmic Ray Group at the Massachusetts Institute of Technology. [41] The experiment employed eleven scintillation detectors arranged within a circle 460 metres in diameter on the grounds of the Agassiz Station of the Harvard College Observatory. From that work, and from many other experiments carried out all over the world, the energy spectrum of the primary cosmic rays is now known to extend beyond 1020 eV. A huge air shower experiment called the Auger Project is currently operated at a site on the pampas of Argentina by an international consortium of physicists. The project was first led by James Cronin, winner of the 1980 Nobel Prize in Physics from the University of Chicago, and Alan Watson of the University of Leeds, and later by other scientists of the international Pierre Auger Collaboration. Their aim is to explore the properties and arrival directions of the very highest-energy primary cosmic rays. [42] The results are expected to have important implications for particle physics and cosmology, due to a theoretical Greisen–Zatsepin–Kuzmin limit to the energies of cosmic rays from long distances (about 160 million light years) which occurs above 1020 eV because of interactions with the remnant photons from the Big Bang origin of the universe. Currently the Pierre Auger Observatory undergoes an upgrade to improve its accuracy and find evidence for the yet unconfirmed origin of the most energetic cosmic rays.

High-energy gamma rays (>50 MeV photons) were finally discovered in the primary cosmic radiation by an MIT experiment carried on the OSO-3 satellite in 1967. [43] Components of both galactic and extra-galactic origins were separately identified at intensities much less than 1% of the primary charged particles. Since then, numerous satellite gamma-ray observatories have mapped the gamma-ray sky. The most recent is the Fermi Observatory, which has produced a map showing a narrow band of gamma ray intensity produced in discrete and diffuse sources in our galaxy, and numerous point-like extra-galactic sources distributed over the celestial sphere.

Sources

Early speculation on the sources of cosmic rays included a 1934 proposal by Baade and Zwicky suggesting cosmic rays originated from supernovae. [44] A 1948 proposal by Horace W. Babcock suggested that magnetic variable stars could be a source of cosmic rays. [45] Subsequently, in 1951, Y. Sekido et al. identified the Crab Nebula as a source of cosmic rays. [46] Since then, a wide variety of potential sources for cosmic rays began to surface, including supernovae, active galactic nuclei, quasars, and gamma-ray bursts. [47]

Sources of ionizing radiation in interplanetary space. PIA16938-RadiationSources-InterplanetarySpace.jpg
Sources of ionizing radiation in interplanetary space.
Shock front acceleration (theoretical model for supernovae and active galactic nuclei): Incident proton gets accelerated between two shock fronts up to energies of the high-energy component of cosmic rays. Shockfrontacceleration.svg
Shock front acceleration (theoretical model for supernovae and active galactic nuclei): Incident proton gets accelerated between two shock fronts up to energies of the high-energy component of cosmic rays.

Later experiments have helped to identify the sources of cosmic rays with greater certainty. In 2009, a paper presented at the International Cosmic Ray Conference (ICRC) by scientists at the Pierre Auger Observatory showed ultra-high energy cosmic rays (UHECRs) originating from a location in the sky very close to the radio galaxy Centaurus A, although the authors specifically stated that further investigation would be required to confirm Cen A as a source of cosmic rays. [48] However, no correlation was found between the incidence of gamma-ray bursts and cosmic rays, causing the authors to set upper limits as low as 3.4 × 10−6 erg·cm−2 on the flux of 1 GeV – 1 TeV cosmic rays from gamma-ray bursts. [49]

In 2009, supernovae were said to have been "pinned down" as a source of cosmic rays, a discovery made by a group using data from the Very Large Telescope. [50] This analysis, however, was disputed in 2011 with data from PAMELA, which revealed that "spectral shapes of [hydrogen and helium nuclei] are different and cannot be described well by a single power law", suggesting a more complex process of cosmic ray formation. [51] In February 2013, though, research analyzing data from Fermi revealed through an observation of neutral pion decay that supernovae were indeed a source of cosmic rays, with each explosion producing roughly 3 × 1042 – 3 × 1043  J of cosmic rays. [3] [4] However, supernovae do not produce all cosmic rays, and the proportion of cosmic rays that they do produce is a question which cannot be answered without further study. [52] As an explanation of the acceleration in supernovae and active galactic nuclei the model of shock front acceleration is used.

In 2017 the Pierre Auger Collaboration published the observation of a weak anisotropy in the arrival directions of the highest energy comsic rays. [53] Since the Galactic Center is in the deficit region, this anisotropy can be interpreted as evidence for the extragalactic origin of cosmic rays at the highest energies. This implies that there must be a transition energy from galactic to extragalactic sources, and there may be different types of cosmic-ray sources contributing to different energy ranges.

Types

Cosmic rays can be divided into three types, galactic cosmic rays (GCR) and extragalactic cosmic rays, i.e., high-energy particles originating outside the solar system, and solar energetic particles , high-energy particles (predominantly protons) emitted by the sun, primarily in solar particle events. However, the term "cosmic ray" is often used to refer to only the extrasolar flux.

Primary cosmic particle collides with a molecule of atmosphere. Atmospheric Collision.svg
Primary cosmic particle collides with a molecule of atmosphere.

Cosmic rays originate as primary cosmic rays, which are those originally produced in various astrophysical processes. Primary cosmic rays are composed primarily of protons and alpha particles (99%), with a small amount of heavier nuclei (~1%) and an extremely minute proportion of positrons and antiprotons. [8] Secondary cosmic rays, caused by a decay of primary cosmic rays as they impact an atmosphere, include photons, leptons, and hadrons, such as electrons, positrons, muons, and pions. The latter three of these were first detected in cosmic rays.

Primary cosmic rays

Primary cosmic rays primarily originate from outside the Solar system and sometimes even the Milky Way. When they interact with Earth's atmosphere, they are converted to secondary particles. The mass ratio of helium to hydrogen nuclei, 28%, is similar to the primordial elemental abundance ratio of these elements, 24%. [54] The remaining fraction is made up of the other heavier nuclei that are typical nucleosynthesis end products, primarily lithium, beryllium, and boron. These nuclei appear in cosmic rays in much greater abundance (~1%) than in the solar atmosphere, where they are only about 10−11 as abundant as helium. Cosmic rays made up of charged nuclei heavier than helium are called HZE ions. Due to the high charge and heavy nature of HZE ions, their contribution to an astronaut's radiation dose in space is significant even though they are relatively scarce.

This abundance difference is a result of the way secondary cosmic rays are formed. Carbon and oxygen nuclei collide with interstellar matter to form lithium, beryllium and boron in a process termed cosmic ray spallation. Spallation is also responsible for the abundances of scandium, titanium, vanadium, and manganese ions in cosmic rays produced by collisions of iron and nickel nuclei with interstellar matter. [55]

At high energies the composition changes and heavier nuclei have larger abundances in some energy ranges. Current experiments aim at more accurate measurements of the composition at high energies.

Primary cosmic ray antimatter

Satellite experiments have found evidence of positrons and a few antiprotons in primary cosmic rays, amounting to less than 1% of the particles in primary cosmic rays. These do not appear to be the products of large amounts of antimatter from the Big Bang, or indeed complex antimatter in the universe. Rather, they appear to consist of only these two elementary particles, newly made in energetic processes.

Preliminary results from the presently operating Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station show that positrons in the cosmic rays arrive with no directionality. In September, 2014, new results with almost twice as much data were presented in a talk at CERN and published in Physical Review Letters. [56] [57] A new measurement of positron fraction up to 500 GeV was reported, showing that positron fraction peaks at a maximum of about 16% of total electron+positron events, around an energy of 275±32 GeV. At higher energies, up to 500 GeV, the ratio of positrons to electrons begins to fall again. The absolute flux of positrons also begins to fall before 500 GeV, but peaks at energies far higher than electron energies, which peak about 10 GeV. [58] These results on interpretation have been suggested to be due to positron production in annihilation events of massive dark matter particles. [59]

Cosmic ray antiprotons also have a much higher average energy than their normal-matter counterparts (protons). They arrive at Earth with a characteristic energy maximum of 2 GeV, indicating their production in a fundamentally different process from cosmic ray protons, which on average have only one-sixth of the energy. [60]

There is no evidence of complex antimatter atomic nuclei, such as antihelium nuclei (i.e., anti-alpha particles), in cosmic rays. These are actively being searched for. A prototype of the AMS-02 designated AMS-01, was flown into space aboard the Space Shuttle Discovery on STS-91 in June 1998. By not detecting any antihelium at all, the AMS-01 established an upper limit of 1.1 × 10−6 for the antihelium to helium flux ratio. [61]

The moon in cosmic rays
Moon's shadow in muons.gif
The Moon's cosmic ray shadow, as seen in secondary muons detected 700 m below ground, at the Soudan 2 detector
Moon egret.jpg
The Moon as seen by the Compton Gamma Ray Observatory, in gamma rays with energies greater than 20 MeV. These are produced by cosmic ray bombardment on its surface. [62]

Secondary cosmic rays

When cosmic rays enter the Earth's atmosphere they collide with atoms and molecules, mainly oxygen and nitrogen. The interaction produces a cascade of lighter particles, a so-called air shower secondary radiation that rains down, including x-rays, muons, protons, alpha particles, pions, electrons, and neutrons. [63] All of the produced particles stay within about one degree of the primary particle's path.

Typical particles produced in such collisions are neutrons and charged mesons such as positive or negative pions and kaons. Some of these subsequently decay into muons and neutrinos, which are able to reach the surface of the Earth. Some high-energy muons even penetrate for some distance into shallow mines, and most neutrinos traverse the Earth without further interaction. Others decay into photon, subsequently producing electromagnetic cascases. Hence, next to photons electrons and positrons usually dominate in air showers. These particles as well as muons can be easily detected by many types of particle detectors, such as cloud chambers, bubble chambers, water-Cherenkov or scintillation detectors. The observation of a secondary shower of particles in multiple detectors at the same time is an indication that all of the particles came from that event.

Cosmic rays impacting other planetary bodies in the Solar System are detected indirectly by observing high-energy gamma ray emissions by gamma-ray telescope. These are distinguished from radioactive decay processes by their higher energies above about 10 MeV.

Cosmic-ray flux

An overview of the space environment shows the relationship between the solar activity and galactic cosmic rays. SpaceEnvironmentOverview From 19830101.jpg
An overview of the space environment shows the relationship between the solar activity and galactic cosmic rays.

The flux of incoming cosmic rays at the upper atmosphere is dependent on the solar wind, the Earth's magnetic field, and the energy of the cosmic rays. At distances of ~94  AU from the Sun, the solar wind undergoes a transition, called the termination shock, from supersonic to subsonic speeds. The region between the termination shock and the heliopause acts as a barrier to cosmic rays, decreasing the flux at lower energies (≤ 1 GeV) by about 90%. However, the strength of the solar wind is not constant, and hence it has been observed that cosmic ray flux is correlated with solar activity.

In addition, the Earth's magnetic field acts to deflect cosmic rays from its surface, giving rise to the observation that the flux is apparently dependent on latitude, longitude, and azimuth angle.

The combined effects of all of the factors mentioned contribute to the flux of cosmic rays at Earth's surface. The following table of participial frequencies reach the planet [65] and are inferred from lower energy radiation reaching the ground. [66]

Particle energy (eV)Particle rate (m−2s−1)
1×109 (GeV)1×104
1×1012 (TeV)1
1×1016 (10 PeV)1×10−7 (a few times a year)
1×1020 (100 EeV)1×10−15 (once a century)

In the past, it was believed that the cosmic ray flux remained fairly constant over time. However, recent research suggests one-and-a-half- to two-fold millennium-timescale changes in the cosmic ray flux in the past forty thousand years. [67]

The magnitude of the energy of cosmic ray flux in interstellar space is very comparable to that of other deep space energies: cosmic ray energy density averages about one electron-volt per cubic centimetre of interstellar space, or ~1 eV/cm3, which is comparable to the energy density of visible starlight at 0.3 eV/cm3, the galactic magnetic field energy density (assumed 3 microgauss) which is ~0.25 eV/cm3, or the cosmic microwave background (CMB) radiation energy density at ~ 0.25 eV/cm3. [68]

Detection methods

The VERITAS array of air Cherenkov telescopes. VERITAS array.jpg
The VERITAS array of air Cherenkov telescopes.

There are two main classes of detection methods. First, the direct detection of the primary cosmic rays in space or at high altitude by balloon-borne instruments. Second, the indirect detection of secondary particle, i.e., extensive air showers at higher energies. While there have been proposals and prototypes for space and ballon-borne detection of air showers, currently operating experiments for high-energy cosmic rays are ground based. Generally direct detection is more accurate than indirect detection. However the flux of cosmic rays decreases with energy, which hampers direct detection for the energy range above 1 PeV. Both, direct and indirect detection, is realized by several techniques.

Direct detection

Direct detection is possible by all kind of particle detectors at the ISS, on satellites, or high-altitude balloons. However, there are constrains in weight and size limiting the choices of detectors.

An example for the direct detection technique is a method developed by Robert Fleischer, P. Buford Price, and Robert M. Walker for use in high-altitude balloons. [69] In this method, sheets of clear plastic, like 0.25  mm Lexan polycarbonate, are stacked together and exposed directly to cosmic rays in space or high altitude. The nuclear charge causes chemical bond breaking or ionization in the plastic. At the top of the plastic stack the ionization is less, due to the high cosmic ray speed. As the cosmic ray speed decreases due to deceleration in the stack, the ionization increases along the path. The resulting plastic sheets are "etched" or slowly dissolved in warm caustic sodium hydroxide solution, that removes the surface material at a slow, known rate. The caustic sodium hydroxide dissolves the plastic at a faster rate along the path of the ionized plastic. The net result is a conical etch pit in the plastic. The etch pits are measured under a high-power microscope (typically 1600× oil-immersion), and the etch rate is plotted as a function of the depth in the stacked plastic.

This technique yields a unique curve for each atomic nucleus from 1 to 92, allowing identification of both the charge and energy of the cosmic ray that traverses the plastic stack. The more extensive the ionization along the path, the higher the charge. In addition to its uses for cosmic-ray detection, the technique is also used to detect nuclei created as products of nuclear fission.

Indirect detection

There are several ground-based methods of detecting cosmic rays currently in use, which can be divided in two main categories: the detection of secondary particles forming extensive air showers (EAS) by various types of particle detectors, and the detection of electromagnetic radiation emitted by EAS in the atmosphere.

Extensive air shower arrays made of particle detectors measure the charged particles which pass through them. EAS arrays can observe a broad area of the sky and can be active more than 90% of the time. However, they are less able to segregate background effects from cosmic rays than can air Cherenkov telescopes. Most state-of-the-art EAS arrays employ plastic scintillators. Also water (liquid or frozen) is used as a detection medium through which particles pass and produce Cherenkov radiation to make them detectable. [70] . Therefore, several arrays use water/ice-Cherenkov detectors as alternative or in addition to scintillators. By the combination of several detectors, some EAS arrays have the capability to distinguish muons from lighter secondary particles (photons, electrons, positrons). The fraction of muons among the secondary particles in one traditional way to estimate the mass composition of the primary cosmic rays.

A historic method of secondary particle detection still used for demonstration purposes involves the use of cloud chambers [71] to detect the secondary muons created when a pion decays. Cloud chambers in particular can be built from widely available materials and can be constructed even in a high-school laboratory. A fifth method, involving bubble chambers, can be used to detect cosmic ray particles. [72]

More recently, the CMOS devices in pervasive smartphone cameras have been proposed as a practical distributed network to detect air showers from ultra-high-energy cosmic rays (UHECRs). [73] The first app, to exploit this proposition was the CRAYFIS (Cosmic RAYs Found In Smartphones) experiment. [74] [75] Then, in 2017, the CREDO (Cosmic Ray Extremely Distributed Observatory) Collaboration [76] released the first version of its completely open source app for Android devices. Since then the collaboration has attracted the interest and support of many scientific institutions, educational institutions and members of the public around the world [77] . Future research has to show in what aspects this new technique can compete with dedicated EAS arrays.


The first detection method in the second category is called the air Cherenkov telescope, designed to detect low-energy (<200 GeV) cosmic rays by means of analyzing their Cherenkov radiation, which for cosmic rays are gamma rays emitted as they travel faster than the speed of light in their medium, the atmosphere. [78] While these telescopes are extremely good at distinguishing between background radiation and that of cosmic-ray origin, they can only function well on clear nights without the Moon shining, and have very small fields of view and are only active for a few percent of the time.

A second method detects the light from nitrogen fluorescence caused by the excitation of nitrogen in the atmosphere by the shower of particles moving through the atmosphere. This method is the most accurate for cosmic rays at highest energies, in particular when combined with EAS arrays of particle detectors. [79] As the detection of Cherenkov-light, this method is restricted to clear nights.

Another method detects radio waves emitted by air showers. This technique has a high duty cycle similar to that of particle detectors. The accuracy of this technique was improved in the last years as shown by various prototype experiments, and may become an alternative to the detection of atmospheric Cherenkov-light and fluorescence light, at least at high energies.


Effects

Changes in atmospheric chemistry

Cosmic rays ionize the nitrogen and oxygen molecules in the atmosphere, which leads to a number of chemical reactions. Cosmic rays are also responsible for the continuous production of a number of unstable isotopes in the Earth's atmosphere, such as carbon-14, via the reaction:

n + 14N → p + 14C

Cosmic rays kept the level of carbon-14 [80] in the atmosphere roughly constant (70 tons) for at least the past 100,000 years,[ citation needed ] until the beginning of above-ground nuclear weapons testing in the early 1950s. This is an important fact used in radiocarbon dating used in archaeology.

Reaction products of primary cosmic rays, radioisotope half-lifetime, and production reaction. [81]
  • Tritium (12.3 years): 14N(n, 3H)12C (spallation)
  • Beryllium-7 (53.3 days)
  • Beryllium-10 (1.39 million years): 14N(n,p α)10Be (spallation)
  • Carbon-14 (5730 years): 14N(n, p)14C (neutron activation)
  • Sodium-22 (2.6 years)
  • Sodium-24 (15 hours)
  • Magnesium-28 (20.9 hours)
  • Silicon-31 (2.6 hours)
  • Silicon-32 (101 years)
  • Phosphorus-32 (14.3 days)
  • Sulfur-35 (87.5 days)
  • Sulfur-38 (2.84 hours)
  • Chlorine-34 m (32 minutes)
  • Chlorine-36 (300,000 years)
  • Chlorine-38 (37.2 minutes)
  • Chlorine-39 (56 minutes)
  • Argon-39 (269 years)
  • Krypton-85 (10.7 years)

Role in ambient radiation

Cosmic rays constitute a fraction of the annual radiation exposure of human beings on the Earth, averaging 0.39 mSv out of a total of 3 mSv per year (13% of total background) for the Earth's population. However, the background radiation from cosmic rays increases with altitude, from 0.3 mSv per year for sea-level areas to 1.0 mSv per year for higher-altitude cities, raising cosmic radiation exposure to a quarter of total background radiation exposure for populations of said cities. Airline crews flying long distance high-altitude routes can be exposed to 2.2 mSv of extra radiation each year due to cosmic rays, nearly doubling their total exposure to ionizing radiation.

Average annual radiation exposure (millisieverts)
Radiation UNSCEAR [82] [83] Princeton [84] Wa State [85] MEXT [86] Remark
TypeSourceWorld
average
Typical rangeUSAUSAJapan
NaturalAir1.260.2–10.0a2.292.000.40Primarily from radon,(a)depends on indoor accumulation of radon gas.
Internal0.290.2–1.0b0.160.400.40Mainly from radioisotopes in food (40K, 14C, etc.)(b)depends on diet.
Terrestrial0.480.3–1.0c0.190.290.40(c)Depends on soil composition and building material of structures.
Cosmic0.390.3–1.0d0.310.260.30(d)Generally increases with elevation.
Subtotal2.401.0–13.02.952.951.50
ArtificialMedical0.600.03–2.03.000.532.30
Fallout0.0070 – 1+--0.01Peaked in 1963 with a spike in 1986; still high near nuclear test and accident sites.
For the United States, fallout is incorporated into other categories.
Others0.00520–200.250.130.001Average annual occupational exposure is 0.7 mSv; mining workers have higher exposure.
Populations near nuclear plants have an additional ~0.02 mSv of exposure annually.
Subtotal0.60 to tens3.250.662.311
Total3.000 to tens6.203.613.81
Figures are for the time before the Fukushima Daiichi nuclear disaster. Human-made values by UNSCEAR are from the Japanese National Institute of Radiological Sciences, which summarized the UNSCEAR data.

Effect on electronics

Cosmic rays have sufficient energy to alter the states of circuit components in electronic integrated circuits, causing transient errors to occur (such as corrupted data in electronic memory devices or incorrect performance of CPUs) often referred to as "soft errors." This has been a problem in electronics at extremely high-altitude, such as in satellites, but with transistors becoming smaller and smaller, this is becoming an increasing concern in ground-level electronics as well. [87] Studies by IBM in the 1990s suggest that computers typically experience about one cosmic-ray-induced error per 256 megabytes of RAM per month. [88] To alleviate this problem, the Intel Corporation has proposed a cosmic ray detector that could be integrated into future high-density microprocessors, allowing the processor to repeat the last command following a cosmic-ray event. [89]

In 2008, data corruption in a flight control system caused an Airbus A330 airliner to twice plunge hundreds of feet, resulting in injuries to multiple passengers and crew members. Cosmic rays were investigated among other possible causes of the data corruption, but were ultimately ruled out as being very unlikely. [90]

Significance to aerospace travel

Galactic cosmic rays are one of the most important barriers standing in the way of plans for interplanetary travel by crewed spacecraft. Cosmic rays also pose a threat to electronics placed aboard outgoing probes. In 2010, a malfunction aboard the Voyager 2 space probe was credited to a single flipped bit, probably caused by a cosmic ray. Strategies such as physical or magnetic shielding for spacecraft have been considered in order to minimize the damage to electronics and human beings caused by cosmic rays. [91] [92]

Comparison of radiation doses, including the amount detected on the trip from Earth to Mars by the RAD on the MSL (2011 - 2013). PIA17601-Comparisons-RadiationExposure-MarsTrip-20131209.png
Comparison of radiation doses, including the amount detected on the trip from Earth to Mars by the RAD on the MSL (2011 – 2013).

Flying 12 kilometres (39,000 ft) high, passengers and crews of jet airliners are exposed to at least 10 times the cosmic ray dose that people at sea level receive. Aircraft flying polar routes near the geomagnetic poles are at particular risk. [93] [94] [95]

Role in lightning

Cosmic rays have been implicated in the triggering of electrical breakdown in lightning. It has been proposed that essentially all lightning is triggered through a relativistic process, "runaway breakdown", seeded by cosmic ray secondaries. Subsequent development of the lightning discharge then occurs through "conventional breakdown" mechanisms. [96]

Postulated role in climate change

A role for cosmic rays in climate was suggested by Edward P. Ney in 1959 [97] and by Robert E. Dickinson in 1975. [98] It has been postulated that cosmic rays may have been responsible for major climatic change and mass-extinction in the past. According to Adrian Mellott and Mikhail Medvedev, 62-million-year cycles in biological marine populations correlate with the motion of the Earth relative to the galactic plane and increases in exposure to cosmic rays. [99] The researchers suggest that this and gamma ray bombardments deriving from local supernovae could have affected cancer and mutation rates, and might be linked to decisive alterations in the Earth's climate, and to the mass-extinctions of the Ordovician. [100] [101]

Danish physicist Henrik Svensmark has controversially argued that because solar variation modulates the cosmic ray flux on Earth, they would consequently affect the rate of cloud formation and hence be an indirect cause of global warming. [102] [103] Svensmark is one of several scientists outspokenly opposed to the mainstream scientific assessment of global warming, leading to concerns that the proposition that cosmic rays are connected to global warming could be ideologically biased rather than scientifically based. [104] Other scientists have vigorously criticized Svensmark for sloppy and inconsistent work: one example is adjustment of cloud data that understates error in lower cloud data, but not in high cloud data; [105] another example is "incorrect handling of the physical data" resulting in graphs that do not show the correlations they claim to show. [106] Despite Svensmark's assertions, galactic cosmic rays have shown no statistically significant influence on changes in cloud cover, [107] and demonstrated to have no causal relationship to changes in global temperature. [108]

Possible mass extinction factor

A handful of studies conclude that a nearby supernova or series of supernovas caused the Pliocene marine megafauna extinction event by substantially increasing radiation levels to hazardous amounts for large seafaring animals. [109] [110] [111]

Research and experiments

There are a number of cosmic-ray research initiatives, listed below.

Ground-based

Satellite

Balloon-borne

See also

Related Research Articles

Antimatter Material composed of the antiparticles of the corresponding particles of ordinary matter

In modern physics, antimatter is defined as a material composed of the antiparticles of the corresponding particles of ordinary matter. Microscopic numbers of antiparticles are generated daily at particle accelerators and in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form anti-atoms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling.

Positron subatomic particle with positive charge

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1 e, a spin of 1/2, and has the same mass as an electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more gamma ray photons.

Radiation waves or particles propagating through space or through a medium, carrying energy

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:

Pion lightest meson

In particle physics, a pion is any of three subatomic particles:
π0
,
π+
, and
π
. Each pion consists of a quark and an antiquark and is therefore a meson. Pions are the lightest mesons and, more generally, the lightest hadrons. They are unstable, with the charged pions
π+
and
π
decaying with a mean lifetime of 26.033 nanoseconds, and the neutral pion
π0
decaying with a much shorter lifetime of 8.4×10−17 seconds. Charged pions most often decay into muons and muon neutrinos, while neutral pions generally decay into gamma rays.

The Greisen–Zatsepin–Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy. The limit is 5×1019 eV, or about 8 joules. The limit is set by slowing interactions of the protons with the microwave background radiation over long distances (~160 million light-years). The limit is at the same order of magnitude as the upper limit for energy at which cosmic rays have experimentally been detected. For example, one extreme-energy cosmic ray has been detected which appeared to possess a record 3.12×1020 eV (50 joules) of energy (about the same as the kinetic energy of a 95 km/h baseball).

Neutrino astronomy observational astronomy that benefits from the direct, or indirect, detection of neutrinos

Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories. Neutrinos are created as a result of certain types of radioactive decay, or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. Due to their weak interactions with matter, neutrinos offer a unique opportunity to observe processes that are inaccessible to optical telescopes.

Photodetector sensors of light or other electromagnetic energy

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. A photo detector has a p–n junction that converts light photons into current. The absorbed photons make electron–hole pairs in the depletion region. Photodiodes and photo transistors are a few examples of photo detectors. Solar cells convert some of the light energy absorbed into electrical energy.

Air shower (physics) shower of particles from a high energy cosmic ray hitting Earths atmosphere

An air shower is an extensive cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray enters the atmosphere. When a particle, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, strikes an atom's nucleus in the air it produces many energetic hadrons. The unstable hadrons decay in the air speedily into other particles and electromagnetic radiation, which are part of the shower components. The secondary radiation rains down, including x-rays, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons.

Pierre Auger Observatory observatory

The Pierre Auger Observatory is an international cosmic ray observatory in Argentina designed to detect ultra-high-energy cosmic rays: sub-atomic particles traveling nearly at the speed of light and each with energies beyond 1018 eV. In Earth's atmosphere such particles interact with air nuclei and produce various other particles. These effect particles (called an "air shower") can be detected and measured. But since these high energy particles have an estimated arrival rate of just 1 per km2 per century, the Auger Observatory has created a detection area of 3,000 km2 (1,200 sq mi)—the size of Rhode Island, or Luxembourg—in order to record a large number of these events. It is located in the western Mendoza Province, Argentina, near the Andes.

PAMELA detector

PAMELA was a cosmic ray research module attached to an Earth orbiting satellite. PAMELA was launched on 15 June 2006 and was the first satellite-based experiment dedicated to the detection of cosmic rays, with a particular focus on their antimatter component, in the form of positrons and antiprotons. Other objectives included long-term monitoring of the solar modulation of cosmic rays, measurements of energetic particles from the Sun, high-energy particles in Earth's magnetosphere and Jovian electrons. It was also hoped that it may detect evidence of dark matter annihilation. PAMELA operations were terminated in 2016, as were the operations of the host-satellite Resurs-DK1.

In particle physics, a shower is a cascade of secondary particles produced as the result of a high-energy particle interacting with dense matter. The incoming particle interacts, producing multiple new particles with lesser energy; each of these then interacts, in the same way, a process that continues until many thousands, millions, or even billions of low-energy particles are produced. These are then stopped in the matter and absorbed.

Cosmic-ray observatory

A cosmic-ray observatory is a scientific installation built to detect high-energy-particles coming from space called cosmic rays. This typically includes photons, electrons, protons, and some heavier nuclei, as well as antimatter particles. About 90% of cosmic rays are protons, 9% are alpha particles, and the remaining ~1% are other particles.

A neutron monitor is a ground-based detector designed to measure the number of high-energy charged particles striking the Earth's atmosphere from outer space. For historical reasons the incoming particles are called "cosmic rays", but in fact they are particles, predominantly protons and Helium nuclei. Most of the time, a neutron monitor records galactic cosmic rays and their variation with the 11-year sunspot cycle and 22-year magnetic cycle. Occasionally the Sun emits cosmic rays of sufficient energy and intensity to raise radiation levels on Earth's surface to the degree that they are readily detected by neutron monitors. They are termed "ground level enhancements" (GLE).

Very-high-energy gamma ray

Very-high-energy gamma ray (VHEGR) denotes gamma radiation with photon energies of 100 GeV (Gigaelectronvolt) to 100 TeV (Teraelectronvolt), i.e., 1011 to 1014 electronvolts. This is approximately equal to wavelengths between 10−17 and 10−20 meters, or frequencies of 2 × 1025 to 2 × 1028 Hz. Such energy levels have been detected from emissions from astronomical sources such as some binary star systems containing a compact object. For example, radiation emitted from Cygnus X-3 has been measured at ranges from GeV to exaelectronvolt-levels. Other astronomical sources include BL Lacertae, 3C 66A Markarian 421 and Markarian 501. Various other sources exist that are not associated with known bodies. For example, the H.E.S.S. catalog contains 64 sources in November 2011.

Tests of relativistic energy and momentum

Tests of relativistic energy and momentum are aimed at measuring the relativistic expressions for energy, momentum, and mass. According to special relativity, the properties of particles moving approximately at the speed of light significantly deviate from the predictions of Newtonian mechanics. For instance, the speed of light cannot be reached by massive particles.

References

  1. Sharma (2008). Atomic And Nuclear Physics. Pearson Education India. p. 478. ISBN   978-81-317-1924-4.
  2. "Detecting cosmic rays from a galaxy far, far away". Science Daily. 21 September 2017. Retrieved 26 December 2017.
  3. 1 2 Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E.D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Busetto, G.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Celik, O.; Charles, E.; et al. (2013-02-15). "Detection of the Characteristic Pion-Decay Signature in Supernova Remnants". Science. 339 (6424): 807–811. arXiv: 1302.3307 . Bibcode:2013Sci...339..807A. doi:10.1126/science.1231160. PMID   23413352.
  4. 1 2 Ginger Pinholster (2013-02-13). "Evidence Shows that Cosmic Rays Come from Exploding Stars".
  5. HESS collaboration (2016). "Acceleration of petaelectronvolt protons in the Galactic Centre". Nature . 531 (7595): 476–479. arXiv: 1603.07730 . Bibcode:2016Natur.531..476H. doi:10.1038/nature17147. PMID   26982725.
  6. Collaboration, IceCube (2018-07-12). "Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert". Science. 361 (6398): 147–151. arXiv: 1807.08794 . Bibcode:2018Sci...361..147I. doi:10.1126/science.aat2890. ISSN   0036-8075. PMID   30002248.
  7. Eric Christian. "Are Cosmic Rays Electromagnetic radiation?". NASA. Retrieved 2012-12-11.
  8. 1 2 "What are cosmic rays?". NASA, Goddard Space Flight Center. Archived from the original on 28 October 2012. Retrieved 31 October 2012. copy
  9. H. Dembinski; et al. (2018). "Data-driven model of the cosmic-ray flux and mass composition from 10 GeV to 10^11 GeV". Proceedings of Science . ICRC2017: 533. arXiv: 1711.11432 . doi:10.22323/1.301.0533.
  10. Nerlich, Steve (12 June 2011). "Astronomy Without A Telescope – Oh-My-God Particles". Universe Today. Universe Today. Retrieved 17 February 2013.
  11. "Facts and figures". The LHC. European Organization for Nuclear Research. 2008. Retrieved 17 February 2013.
  12. Gaensler, Brian (November 2011). "Extreme speed". COSMOS (41). Archived from the original on 2013-04-07.
  13. L. Anchordoqui; T. Paul; S. Reucroft; J. Swain (2003). "Ultrahigh Energy Cosmic Rays: The state of the art before the Auger Observatory". International Journal of Modern Physics A . 18 (13): 2229–2366. arXiv: hep-ph/0206072 . Bibcode:2003IJMPA..18.2229A. doi:10.1142/S0217751X03013879.
  14. Nave, Carl R. "Cosmic rays". HyperPhysics Concepts. Georgia State University. Retrieved 17 February 2013.
  15. Malley, Marjorie C. (August 25, 2011), Radioactivity: A History of a Mysterious Science, Oxford University Press, pp. 78–79, ISBN   9780199766413.
  16. North, John (July 15, 2008), Cosmos: An Illustrated History of Astronomy and Cosmology, University of Chicago Press, p. 686, ISBN   9780226594415.
  17. D. Pacini (1912). "La radiazione penetrante alla superficie ed in seno alle acque". Il Nuovo Cimento . 3 (1): 93–100. arXiv: 1002.1810 . Bibcode:1912NCim....3...93P. doi:10.1007/BF02957440.
    Translated and commented in A. de Angelis (2010). "Penetrating Radiation at the Surface of and in Water". Il Nuovo Cimento. 3: 93–100. arXiv: 1002.1810 . Bibcode:1912NCim....3...93P. doi:10.1007/BF02957440.
  18. 1 2 3 "Nobel Prize in Physics 1936 – Presentation Speech". Nobelprize.org. 1936-12-10. Retrieved 2013-02-27.
  19. V. F. Hess (1912). "Über Beobachtungen der durchdringenden Strahlung bei sieben Freiballonfahrten (English translation)". Physikalische Zeitschrift. 13: 1084–1091. arXiv: 1808.02927 .
  20. V.F. Hess (1936). "The Nobel Prize in Physics 1936". The Nobel Foundation . Retrieved 2010-02-11.
  21. V.F. Hess (1936). "Unsolved Problems in Physics: Tasks for the Immediate Future in Cosmic Ray Studies". Nobel Lectures. The Nobel Foundation . Retrieved 2010-02-11.
  22. 1 2 Kerr, Richard (31 May 2013). "Radiation Will Make Astronauts' Trip to Mars Even Riskier". Science . 340 (6136): 1031. doi:10.1126/science.340.6136.1031. PMID   23723213.
  23. 1 2 Zeitlin, C.; Hassler, D. M.; Cucinotta, F. A.; Ehresmann, B.; Wimmer-Schweingruber, R. F.; Brinza, D. E.; Kang, S.; Weigle, G.; et al. (31 May 2013). "Measurements of Energetic Particle Radiation in Transit to Mars on the Mars Science Laboratory". Science . 340 (6136): 1080–1084. Bibcode:2013Sci...340.1080Z. doi:10.1126/science.1235989. PMID   23723233.
  24. 1 2 Chang, Kenneth (30 May 2013). "Data Point to Radiation Risk for Travelers to Mars". The New York Times . Retrieved 31 May 2013.
  25. Rossi, Bruno Benedetto (1964). Cosmic Rays. New York: McGraw-Hill. ISBN   978-0-07-053890-0.
  26. Geiger, H.; Rutherford, Lord; Regener, E.; Lindemann, F. A.; Wilson, C. T. R.; Chadwick, J.; Gray, L. H.; Tarrant, G. T. P.; et al. (1931). "Discussion on Ultra-Penetrating Rays". Proceedings of the Royal Society of London A. 132 (819): 331. Bibcode:1931RSPSA.132..331G. doi:10.1098/rspa.1931.0104.
  27. Clay, J. (1927). "Penetrating Radiation" (PDF). Proceedings of the Section of Sciences, Koninklijke Akademie van Wetenschappen Te Amsterdam. 30 (9–10): 1115–1127.
  28. Bothe, Walther; Werner Kolhörster (November 1929). "Das Wesen der Höhenstrahlung". Zeitschrift für Physik. 56 (11–12): 751–777. Bibcode:1929ZPhy...56..751B. doi:10.1007/BF01340137.
  29. Rossi, Bruno (August 1930). "On the Magnetic Deflection of Cosmic Rays". Physical Review. 36 (3): 606. Bibcode:1930PhRv...36..606R. doi:10.1103/PhysRev.36.606.
  30. Johnson, Thomas H. (May 1933). "The Azimuthal Asymmetry of the Cosmic Radiation". Physical Review. 43 (10): 834–835. Bibcode:1933PhRv...43..834J. doi:10.1103/PhysRev.43.834.
  31. Alvarez, Luis; Compton, Arthur Holly (May 1933). "A Positively Charged Component of Cosmic Rays". Physical Review. 43 (10): 835–836. Bibcode:1933PhRv...43..835A. doi:10.1103/PhysRev.43.835.
  32. Rossi, Bruno (May 1934). "Directional Measurements on the Cosmic Rays Near the Geomagnetic Equator". Physical Review. 45 (3): 212–214. Bibcode:1934PhRv...45..212R. doi:10.1103/PhysRev.45.212.
  33. Freier, Phyllis; Lofgren, E.; Ney, E.; Oppenheimer, F.; Bradt, H.; Peters, B.; et al. (July 1948). "Evidence for Heavy Nuclei in the Primary Cosmic radiation". Physical Review. 74 (2): 213–217. Bibcode:1948PhRv...74..213F. doi:10.1103/PhysRev.74.213.
  34. Freier, Phyllis; Peters, B.; et al. (December 1948). "Investigation of the Primary Cosmic Radiation with Nuclear Photographic Emulsions". Physical Review. 74 (12): 1828–1837. Bibcode:1948PhRv...74.1828B. doi:10.1103/PhysRev.74.1828.
  35. Rossi, Bruno (1934). "Misure sulla distribuzione angolare di intensita della radiazione penetrante all'Asmara". Ricerca Scientifica. 5 (1): 579–589.
  36. Auger, P.; et al. (July 1939), "Extensive Cosmic-Ray Showers", Reviews of Modern Physics, 11 (3–4): 288–291, Bibcode:1939RvMP...11..288A, doi:10.1103/RevModPhys.11.288.
  37. J.L. DuBois; R.P. Multhauf; C.A. Ziegler (2002). The Invention and Development of the Radiosonde (PDF). Smithsonian Studies in History and Technology. 53. Smithsonian Institution Press.
  38. S. Vernoff (1935). "Radio-Transmission of Cosmic Ray Data from the Stratosphere". Nature . 135 (3426): 1072–1073. Bibcode:1935Natur.135.1072V. doi:10.1038/1351072c0.
  39. Bhabha, H. J.; Heitler, W. (1937). "The Passage of Fast Electrons and the Theory of Cosmic Showers" (PDF). Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 159 (898): 432–458. Bibcode:1937RSPSA.159..432B. doi:10.1098/rspa.1937.0082. ISSN   1364-5021.
  40. Braunschweig, W.; et al. (1988). "A study of Bhabha scattering at PETRA energies". Zeitschrift für Physik C Particles and Fields. 37 (2): 171–177. doi:10.1007/BF01579904.
  41. Clark, G.; Earl, J.; Kraushaar, W.; Linsley, J.; Rossi, B.; Scherb, F.; Scott, D. (1961). "Cosmic-Ray Air Showers at Sea Level". Physical Review. 122 (2): 637–654. Bibcode:1961PhRv..122..637C. doi:10.1103/PhysRev.122.637.
  42. "The Pierre Auger Observatory". Auger Project. Archived from the original on 13 September 2018.
  43. Kraushaar, W. L.; et al. (1972). "Title unknown". The Astrophysical Journal. 177: 341. Bibcode:1972ApJ...177..341K. doi:10.1086/151713.
  44. Baade, W.; Zwicky, F. (1934). "Cosmic Rays from Super-novae". Proceedings of the National Academy of Sciences of the United States of America. 20 (5): 259–263. Bibcode:1934PNAS...20..259B. doi:10.1073/pnas.20.5.259. JSTOR   86841.
  45. Babcock, H. (1948). "Magnetic Variable Stars as Sources of Cosmic Rays". Physical Review. 74 (4): 489. Bibcode:1948PhRv...74..489B. doi:10.1103/PhysRev.74.489.
  46. Sekido, Y.; Masuda, T.; Yoshida, S.; Wada, M. (1951). "The Crab Nebula as an Observed Point Source of Cosmic Rays". Physical Review. 83 (3): 658–659. Bibcode:1951PhRv...83..658S. doi:10.1103/PhysRev.83.658.2.
  47. Gibb, Meredith (3 February 2010). "Cosmic Rays". Imagine the Universe. NASA Goddard Space Flight Center. Retrieved 17 March 2013.
  48. Hague, J. D. (July 2009). "Correlation of the Highest Energy Cosmic Rays with Nearby Extragalactic Objects in Pierre Auger Observatory Data" (PDF). Proceedings of the 31st ICRC, Łódź 2009. International Cosmic Ray Conference. Łódź, Poland. pp. 6–9. Archived from the original (PDF) on 28 May 2013. Retrieved 17 March 2013.
  49. Hague, J. D. (July 2009). "Correlation of the Highest Energy Cosmic Rays with Nearby Extragalactic Objects in Pierre Auger Observatory Data" (PDF). Proceedings of the 31st ICRC, Łódź, Poland 2009 - International Cosmic Ray Conference: 36–39. Archived from the original (PDF) on 28 May 2013. Retrieved 17 March 2013.
  50. Moskowitz, Clara (25 June 2009). "Source of Cosmic Rays Pinned Down". Space.com. TechMediaNetwork. Retrieved 20 March 2013.
  51. Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bonechi, L.; Bongi, M.; Bonvicini, V.; Borisov, S.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; Consiglio, L.; De Pascale, M. P.; De Santis, C.; De Simone, N.; Di Felice, V.; Galper, A. M.; Gillard, W.; Grishantseva, L.; Jerse, G.; Karelin, A. V.; Koldashov, S. V.; et al. (2011). "PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra". Science. 332 (6025): 69–72. arXiv: 1103.4055 . Bibcode:2011Sci...332...69A. doi:10.1126/science.1199172. hdl:2108/55474. PMID   21385721.
  52. Jha, Alok (14 February 2013). "Cosmic ray mystery solved". The Guardian. Guardian News and Media Limited. Retrieved 21 March 2013.
  53. The Pierre Auger Collaboration (2017). "Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above 8×10^18 eV". Science. 357 (6357): 1266–1270. arXiv: 1709.07321 . doi:10.1126/science.aan4338. PMID   28935800.
  54. Mewaldt, Richard A. (1996). "Cosmic Rays". California Institute of Technology.
  55. Koch, L.; Engelmann, J. J.; Goret, P.; Juliusson, E.; Petrou, N.; Rio, Y.; Soutoul, A.; Byrnak, B.; Lund, N.; Peters, B. (October 1981). "The relative abundances of the elements scandium to manganese in relativistic cosmic rays and the possible radioactive decay of manganese 54". Astronomy and Astrophysics. 102 (11): L9. Bibcode:1981A&A...102L...9K.
  56. L. Accardo (AMS Collaboration); et al. (18 September 2014). "High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–500 GeV with the Alpha Magnetic Spectrometer on the International Space Station" (PDF). Physical Review Letters. 113 (12): 121101. Bibcode:2014PhRvL.113l1101A. doi:10.1103/PhysRevLett.113.121101. PMID   25279616.
  57. Schirber, Michael (2014). "Synopsis: More Dark Matter Hints from Cosmic Rays?". Physical Review Letters. 113 (12): 121102. arXiv: 1701.07305 . Bibcode:2014PhRvL.113l1102A. doi:10.1103/PhysRevLett.113.121102. PMID   25279617.
  58. "New results from the Alpha Magnetic$Spectrometer on the International Space Station" (PDF). AMS-02 at NASA. Retrieved 21 September 2014.
  59. Aguilar, M.; Alberti, G.; Alpat, B.; Alvino, A.; Ambrosi, G.; Andeen, K.; Anderhub, H.; Arruda, L.; Azzarello, P.; Bachlechner, A.; Barao, F.; Baret, B.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Basili, A.; Batalha, L.; Bates, J.; Battiston, R.; Bazo, J.; Becker, R.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Berges, P.; Bertucci, B.; Bigongiari, G.; et al. (2013). "First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–350 GeV" (PDF). Physical Review Letters. 110 (14): 141102. Bibcode:2013PhRvL.110n1102A. doi:10.1103/PhysRevLett.110.141102. PMID   25166975.
  60. Moskalenko, I. V.; Strong, A. W.; Ormes, J. F.; Potgieter, M. S. (January 2002). "Secondary antiprotons and propagation of cosmic rays in the Galaxy and heliosphere". The Astrophysical Journal. 565 (1): 280–296. arXiv: astro-ph/0106567 . Bibcode:2002ApJ...565..280M. doi:10.1086/324402.
  61. AMS Collaboration; Aguilar, M.; Alcaraz, J.; Allaby, J.; Alpat, B.; Ambrosi, G.; Anderhub, H.; Ao, L.; et al. (August 2002). "The Alpha Magnetic Spectrometer (AMS) on the International Space Station: Part I – results from the test flight on the space shuttle". Physics Reports. 366 (6): 331–405. Bibcode:2002PhR...366..331A. doi:10.1016/S0370-1573(02)00013-3. hdl:2078.1/72661.
  62. "EGRET Detection of Gamma Rays from the Moon". NASA/GSFC. 1 August 2005. Retrieved 2010-02-11.
  63. Morison, Ian (2008). Introduction to Astronomy and Cosmology. John Wiley & Sons. p. 198. Bibcode:2008iac..book.....M. ISBN   978-0-470-03333-3.
  64. "Extreme Space Weather Events". National Geophysical Data Center.
  65. "Pierre Auger Observatory". Auger.org. Archived from the original on 12 October 2012. Retrieved 17 August 2012.
  66. "The Mystery of High-Energy Cosmic Rays". Pierre Auger Observatory. Auger.org.
  67. D. Lal; A.J.T. Jull; D. Pollard; L. Vacher (2005). "Evidence for large century time-scale changes in solar activity in the past 32 Kyr, based on in-situ cosmogenic 14C in ice at Summit, Greenland". Earth and Planetary Science Letters . 234 (3–4): 335–349. Bibcode:2005E&PSL.234..335L. doi:10.1016/j.epsl.2005.02.011.
  68. Castellina, Antonella; Donato, Fiorenza (2012). Oswalt, T.D.; McLean, I.S.; Bond, H.E.; French, L.; Kalas, P.; Barstow, M.; Gilmore, G.F.; Keel, W., eds. Planets, Stars, and Stellar Systems (1 ed.). Springer. ISBN   978-90-481-8817-8.
  69. R.L. Fleischer; P.B. Price; R.M. Walker (1975). Nuclear tracks in solids: Principles and applications. University of California Press.
  70. "What are cosmic rays?" (PDF). Michigan State University National Superconducting Cyclotron Laboratory. Archived from the original (PDF) on 12 July 2012. Retrieved 23 February 2013.
  71. "Cloud Chambers and Cosmic Rays: A Lesson Plan and Laboratory Activity for the High School Science Classroom" (PDF). Cornell University Laboratory for Elementary-Particle Physics. 2006. Retrieved 23 February 2013.
  72. Chu, W.; Kim, Y.; Beam, W.; Kwak, N. (1970). "Evidence of a Quark in a High-Energy Cosmic-Ray Bubble-Chamber Picture". Physical Review Letters. 24 (16): 917–923. Bibcode:1970PhRvL..24..917C. doi:10.1103/PhysRevLett.24.917.
  73. Timmer, John (13 October 2014). "Cosmic ray particle shower? There's an app for that". Ars Technica.
  74. Collaboration website Archived 14 October 2014 at the Wayback Machine
  75. CRAYFIS detector array paper. Archived 14 October 2014 at the Wayback Machine
  76. Collaboration website
  77. CREDO 'first light' press release.
  78. "The Detection of Cosmic Rays". Milagro Gamma-Ray Observatory. Los Alamos National Laboratory. 3 April 2002. Archived from the original on 5 March 2013. Retrieved 22 February 2013.
  79. Letessier-Selvon, Antoine; Stanev, Todor (2011). "Ultrahigh energy cosmic rays". Reviews of Modern Physics. 83 (3): 907–942. arXiv: 1103.0031 . Bibcode:2011RvMP...83..907L. doi:10.1103/RevModPhys.83.907.
  80. Trumbore, Susan (2000). Noller, J. S.; J. M. Sowers; W. R. Lettis, eds. Quaternary Geochronology: Methods and Applications. Washington, D.C.: American Geophysical Union. pp. 41–59. ISBN   978-0-87590-950-9.
  81. "Natürliche, durch kosmische Strahlung laufend erzeugte Radionuklide" (PDF) (in German). Retrieved 2010-02-11.
  82. UNSCEAR "Sources and Effects of Ionizing Radiation" page 339 retrieved 2011-6-29
  83. Japan NIRS UNSCEAR 2008 report page 8 retrieved 2011-6-29
  84. Princeton.edu "Background radiation" retrieved 2011-6-29
  85. Washington state Dept. of Health "Background radiation" Archived 2 May 2012 at the Wayback Machine retrieved 2011-6-29
  86. Ministry of Education, Culture, Sports, Science, and Technology of Japan "Radiation in environment" retrieved 2011-6-29
  87. IBM experiments in soft fails in computer electronics (1978–1994), from Terrestrial cosmic rays and soft errors, IBM Journal of Research and Development, Vol. 40, No. 1, 1996. Retrieved 16 April 2008.
  88. Scientific American (2008-07-21). "Solar Storms: Fast Facts". Nature Publishing Group.
  89. Intel plans to tackle cosmic ray threat, BBC News Online, 8 April 2008. Retrieved 16 April 2008.
  90. In-flight upset, 154 km west of Learmonth, Western Australia, 7 October 2008, VH-QPA, Airbus A330-303 . (2011). Australian Transport Safety Bureau.
  91. Globus, Al (10 July 2002). "Appendix E: Mass Shielding". Space Settlements: A Design Study. NASA. Retrieved 24 February 2013.
  92. Atkinson, Nancy (24 January 2005). "Magnetic shielding for spacecraft". The Space Review. Retrieved 24 February 2013.
  93. Phillips, Tony (25 October 2013). "The Effects of Space Weather on Aviation". Science News. NASA.
  94. "Converting Cosmic Rays to Sound During a Transatlantic Flight to Zurich" on YouTube
  95. NAIRAS (Nowcast of Atmospheric Ionizing Radiation System)
  96. Runaway Breakdown and the Mysteries of Lightning, Physics Today, May 2005.
  97. Ney, Edward P. (14 February 1959). "Cosmic Radiation and the Weather". Nature. 183 (4659): 451–452. Bibcode:1959Natur.183..451N. doi:10.1038/183451a0.
  98. Dickinson, Robert E. (December 1975). "Solar Variability and the Lower Atmosphere". Bulletin of the American Meteorological Society. 56 (12): 1240–1248. Bibcode:1975BAMS...56.1240D. doi:10.1175/1520-0477(1975)056<1240:SVATLA>2.0.CO;2.
  99. "Ancient Mass Extinctions Caused by Cosmic Radiation, Scientists Say" - National Geographic (2007)
  100. Melott, A.L.; Thomas, B.C. (2009). "Late Ordovician geographic patterns of extinction compared with simulations of astrophysical ionizing radiation damage". Paleobiology. 35 (3): 311–320. arXiv: 0809.0899 . doi:10.1666/0094-8373-35.3.311.
  101. "Did Supernova Explosion Contribute to Earth Mass Extinction?" - Space.com (2016)
  102. Long, Marion (25 June 2007). "Sun's Shifts May Cause Global Warming". Discover . Retrieved 7 July 2013.
  103. Henrik Svensmark (1998). "Influence of Cosmic Rays on Earth's Climate" (PDF). Physical Review Letters . 81 (22): 5027–5030. Bibcode:1998PhRvL..81.5027S. CiteSeerX   10.1.1.522.585 . doi:10.1103/PhysRevLett.81.5027.
  104. Plait, Phil (August 31, 2011). "No, a new study does not show cosmic-rays are connected to global warming". Discover. Kalmbach Publishing. Retrieved 11 January 2018.
  105. Benestad, Rasmus E. "'Cosmoclimatology' – tired old arguments in new clothes" . Retrieved 13 November 2013.
  106. Peter Laut, "Solar activity and terrestrial climate: an analysis of some purported correlations", Journal of Atmospheric and Solar-Terrestrial Physics 65 (2003) 801- 812
  107. Lockwood, Mike (16 May 2012). "Solar Influence on Global and Regional Climates". Surveys in Geophysics. 33 (3–4): 503–534. Bibcode:2012SGeo...33..503L. doi:10.1007/s10712-012-9181-3.
  108. Sloan, T.; Wolfendale, A.W. (7 November 2013). "Cosmic rays, solar activity and the climate". Environmental Research Letters. 8 (4): 045022. Bibcode:2013ERL.....8d5022S. doi:10.1088/1748-9326/8/4/045022.
  109. Melott, Adrian L.; F. Marinho; L. Paulucci (2019). "Muon Radiation Dose and Marine Megafaunal Extinction at the end-Pliocene Supernova". Astrobiology. 19. arXiv: 1712.09367 . doi:10.1089/ast.2018.1902. PMID   30481053.
  110. Benitez, Narciso; et al. (2002). "Evidence for Nearby Supernova Explosions". Phys. Rev. Lett. 88 (8): 081101. arXiv: astro-ph/0201018 . Bibcode:2002PhRvL..88h1101B. doi:10.1103/PhysRevLett.88.081101. PMID   11863949.
  111. Fimiani, L.; Cook, D.L.; Faestermann, T.; Gómez-Guzmán, J.M.; Hain, K.; Herzog, G.; Knie, K.; Korschinek, G.; Ludwig, P.; Park, J.; Reedy, R.C.; Rugel, G. (2016). "Interstellar 60Fe on the Surface of the Moon". Phys. Rev. Lett. 116 (15): 151104. doi:10.1103/PhysRevLett.116.151104. PMID   27127953.

Further references