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In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo.
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of particle species found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. There are also rarer traces of some other nuclei and isotopes such as phosphorus, titanium, chromium, and nickel's isotopes 58Ni, 60Ni, and 62Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface.
The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes others may be temporarily created. The belts are named after James Van Allen, who published an article describing the belts in 1958.
Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ionosphere, thermosphere, and exosphere. Though physically distinct, space weather is analogous to the terrestrial weather of Earth's atmosphere. The term "space weather" was first used in the 1950s and popularized in the 1990s. Later, it prompted research into "space climate", the large-scale and long-term patterns of space weather.
Advanced Composition Explorer is a NASA Explorer program satellite and space exploration mission to study matter comprising energetic particles from the solar wind, the interplanetary medium, and other sources.
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium. The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way. As part of the interplanetary magnetic field, the heliosphere shields the Solar System from significant amounts of cosmic ionizing radiation; uncharged gamma rays are, however, not affected. Its name was likely coined by Alexander J. Dessler, who is credited with the first use of the word in the scientific literature in 1967. The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.
The interplanetary medium (IPM) or interplanetary space consists of the mass and energy which fills the Solar System, and through which all the larger Solar System bodies, such as planets, dwarf planets, asteroids, and comets, move. The IPM stops at the heliopause, outside of which the interstellar medium begins. Before 1950, interplanetary space was widely considered to either be an empty vacuum, or consisting of "aether".
Cluster II was a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of nearly two solar cycles. The mission is composed of four identical spacecraft flying in a tetrahedral formation. As a replacement for the original Cluster spacecraft which were lost in a launch failure in 1996, the four Cluster II spacecraft were successfully launched in pairs in July and August 2000 onboard two Soyuz-Fregat rockets from Baikonur, Kazakhstan. In February 2011, Cluster II celebrated 10 years of successful scientific operations in space. In February 2021, Cluster II celebrated 20 years of successful scientific operations in space. As of March 2023, its mission has been extended until September 2024. The China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2004 to 2007.
The following is a chronology of discoveries concerning the magnetosphere.
Explorer 52, also known as Hawkeye-1, Injun-F, Neutral Point Explorer, IE-D, Ionospheric Explorer-D, was a NASA satellite launched on June 3, 1974, from Vandenberg Air Force Base on a Scout E-1 launch vehicle.
Heliophysics is the physics of the Sun and its connection with the Solar System. NASA defines heliophysics as "(1) the comprehensive new term for the science of the Sun - Solar System Connection, (2) the exploration, discovery, and understanding of Earth's space environment, and (3) the system science that unites all of the linked phenomena in the region of the cosmos influenced by a star like our Sun."
The magnetosphere of Jupiter is the cavity created in the solar wind by Jupiter's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973.
The Van Allen Probes, formerly known as the Radiation Belt Storm Probes (RBSP), were two robotic spacecraft that were used to study the Van Allen radiation belts that surround Earth. NASA conducted the Van Allen Probes mission as part of the Living With a Star program. Understanding the radiation belt environment and its variability has practical applications in the areas of spacecraft operations, spacecraft system design, mission planning and astronaut safety. The probes were launched on 30 August 2012 and operated for seven years. Both spacecraft were deactivated in 2019 when they ran out of fuel. They are expected to deorbit during the 2030s.
Dynamics Explorer was a NASA mission, launched on 3 August 1981, and terminated on 28 February 1991. It consisted of two unmanned satellites, DE-1 and DE-2, whose purpose was to investigate the interactions between plasmas in the magnetosphere and those in the ionosphere. The two satellites were launched together into polar coplanar orbits, which allowed them to simultaneously observe the upper and lower parts of the atmosphere.
The Solar Sentinels was a series of proposed space missions to the Sun. Solar Sentinels was proposed in 2006 in conjunction with other Sun missions, and another simpler proposal was submitted in 2008.
Energetic Neutral Atom (ENA) imaging is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere.
The Heliophysics Science Division of the Goddard Space Flight Center (NASA) conducts research on the Sun, its extended Solar System environment, and interactions of Earth, other planets, small bodies, and interstellar gas with the heliosphere. Division research also encompasses geospace—Earth's uppermost atmosphere, the ionosphere, and the magnetosphere—and the changing environmental conditions throughout the coupled heliosphere.
Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. They take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots.
Explorer 12, also called EPE-A or Energetic Particles Explorer-A and as S3), was a NASA satellite built to measure the solar wind, cosmic rays, and the Earth's magnetic field. It was the first of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 16 August 1961, aboard a Thor-Delta launch vehicle. It ceased transmitting on 6 December 1961 due to power failure.
Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) is a planned orbiter mission tasked to study the origins of the solar wind and how it affects Earth. TRACERS was proposed by Craig A. Kletzing at the University of Iowa who served as Principal Investigator until his death in 2023. David M. Miles at the University of Iowa was named as Principal Investigator in his stead. The TRACERS mission received US$115 million in funding from NASA.
References
- ↑ Rycroft, M. J. (14 June 1989). "Solar—terrestrial physics: an overview". Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences. 328 (1598): 39–42. doi:10.1098/rsta.1989.0022.
- ↑ "Space Physics Textbook". 2006-11-26. Archived from the original on December 18, 2008. Retrieved 2008-12-31.
- ↑ Li, W.; Hudson, M.K. (2019). "Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era". J. Geophys. Res. 124 (11): 8319–8351. doi: 10.1029/2018JA025940 .
