STEVE (backronym for Strong Thermal Emission Velocity Enhancement) is an atmospheric optical phenomenon that appears as a purple and green light ribbon in the night sky, named in late 2016 by aurora watchers from Alberta, Canada. According to analysis of satellite data from the European Space Agency's Swarm mission, the phenomenon is caused by a 25 km (16 mi) wide ribbon of hot plasma at an altitude of 450 km (280 mi), with a temperature of 3,000 °C (3,270 K; 5,430 °F) and flowing at a speed of 6 km/s (3.7 mi/s) (compared to 10 m/s (33 ft/s) outside the ribbon). The phenomenon is not rare, but had not been investigated and described scientifically prior to that time. [1] [2] [3]
The STEVE phenomenon has been observed by auroral photographers for decades. [3] Some evidence suggests that STEVE observations may have been recorded as early as 1705. [4] Notations resembling the phenomenon exist in some observations from 1911 to the 1950s by Carl Størmer. [5] [6]
The first accurate determination of the nature of the phenomenon was not made, however, until after members of a Facebook group, Alberta Aurora Chasers, named it, attributed it to a proton aurora, and began calling it a "proton arc". [7] When physics professor Eric Donovan from the University of Calgary saw their photographs and suspected that their determination was incorrect because proton auroras are not visible, [8] he correlated the time and location of the phenomenon with Swarm satellite data and one of the Alberta Aurora Chaser photographers, Song Despins. She provided GPS coordinates from Vimy, Alberta, that helped Donovan link the data to identify the phenomenon. [1]
One of the aurora watchers, photographer Chris Ratzlaff, [9] [10] suggested using the name "Steve" for the phenomenon, in reference to Over the Hedge, an animated comedy movie from 2006. The characters in the movie give the name to a hedge that appears overnight, in order to make it seem more benign. [11] Reports of the heretofore undescribed and unusual "aurora" went viral as an example of citizen science on Aurorasaurus. [12] [13]
During the fall meeting of the American Geophysical Union in December 2016, Robert Lysak suggested using a backronym of "Steve" for the phenomenon that would stand for a "Strong Thermal Emission Velocity Enhancement". [14] That acronym, "STEVE", has been adopted by the team at NASA Goddard Space Flight Center that is studying the phenomenon. [15]
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STEVE phenomena may be spotted further from the poles than the aurora, [16] and as of March 2018, have been observed in the United Kingdom, Canada, Alaska, northern U.S. states, Australia, New Zealand [17] and Denmark. [18] The phenomenon appears as a very narrow arc extending for hundreds or thousands of kilometers, aligned east–west. It generally lasts for twenty minutes to an hour. As of March 2018, STEVE phenomena have only been spotted in the presence of an aurora. None were observed from October 2016 to February 2017, or from October 2017 to February 2018, leading NASA to believe that STEVE phenomena may only appear during certain seasons. [19] However, STEVE phenomena have since been reported and photographed in South Australia during a geomagnetic storm event on 11 October 2024. [20]
A study published in March 2018 by Elizabeth A. MacDonald and co-authors in the peer-reviewed journal, Science Advances , suggested that the STEVE phenomenon accompanies a subauroral ion drift (SAID), [21] a fast-moving stream of extremely hot particles. STEVE marks the first observed visual effect accompanying a SAID. [19]
In August 2018, researchers determined that the skyglow of the phenomenon was not associated with particle precipitation (electrons or ions) and, as a result, could be generated in the ionosphere. [22]
One proposed mechanism for the glow is that excited nitrogen breaks apart and interacts with oxygen to form glowing nitric oxide. [23]
Often, although not always, a STEVE phenomenon is observed above a green, "picket-fence" aurora according to a study published in Geophysical Research Letters. [24] [25] Although the picket-fence aurora is created through precipitation of electrons, they appear outside the auroral oval and so their formation is different from traditional aurora. [26] The study also showed these phenomena appear in both hemispheres simultaneously. Sightings of picket-fence aurora have been made without observations of STEVE. [27]
The green emissions in the picket fence aurora seem to be related to eddies in the supersonic flow of charged particles, similar to the eddies seen in a river that move more slowly than the water around them. Hence, the green bars in the picket fence are moving more slowly than the structures in the purple emissions and some scientists have speculated they could be caused by turbulence in the charged particles from space. [28]
An aurora , also commonly known as the northern lights or southern lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions. Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering the entire sky.
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A whistler is a very low frequency (VLF) electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with maximum frequencies usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. The study of whistlers categorizes them into Pure Note, Diffuse, 2-Hop, and Echo Train types.
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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 was 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 was extended until September 2024. The China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2004 to 2007.
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Ashen light is a hypothesised subtle glow that has been claimed to be seen on the night side of the planet Venus. The phenomenon has not been scientifically confirmed, and theories as to the observed phenomenon's cause are numerous, such as emission of light by Venus, or optical phenomena within the observing telescope itself. A modern hypothesis as to the source of light on Venus suggests it to be associated with lightning, for which there is some evidence on Venus. This theory has fallen out of favour, however, as there is not enough light generated by this lightning so as to be observed. A more recent hypothesis is that it is a form of transient aurorae or airglow caused by unusually high solar activity interacting with the upper Venusian atmosphere.
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.
Canadian Geospace Monitoring (CGSM) is a Canadian space science program that was initiated in 2005. CGSM is funded primarily by the Canadian Space Agency, and consists of networks of imagers, meridian scanning photometers, riometers, magnetometers, digital ionosondes, and High Frequency SuperDARN radars. The overarching objective of CGSM is to provide synoptic observations of the spatio-temporal evolution of the ionospheric thermodynamics and electrodynamics at auroral and polar latitudes over a large region of Canada.
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Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a planned joint venture mission between the European Space Agency and the Chinese Academy of Sciences. SMILE will image for the first time the magnetosphere of the Sun in soft X-rays and UV during up to 40 hours per orbit, improving our understanding of the dynamic interaction between the solar wind and Earth's magnetosphere. The prime science questions of the SMILE mission are
Gordon Greeley Shepherd is a Canadian space scientist, currently a Distinguished Research Professor Emeritus at York University
Elizabeth MacDonald is a space weather scientist who works at NASA Goddard Space Flight Center. She is a co-investigator on the Helium, Oxygen, Proton, and Electron Spectrometer on the NASA Radiation Belts Storm Probe mission.
John Clifford Bird is a Canadian engineer, scientist, and journalist. Bird’s research has included laser physics, atmospheric physics, and materials in microgravity. He broke the world altitude record for hang gliding by launching from a helium balloon at 35,000 ft, and spent a year at the Amundsen–Scott South Pole Station, which was documented in his book One Day, One Night: Portraits of the South Pole.
A subauroral ion drift (SAID), also known as a polarisation jet, is an atmospheric phenomenon driven by substorms in the Earth's magnetosphere. First discovered in 1971, a SAID is a latitudinally narrow layer of rapid, westward flowing ions in the Earth’s ionosphere. Though not traditionally associated with an optical emission, the STEVE discovery paper suggested the first link between this optical emission’s occurrence and that of an extremely fast and hot SAID event.
Cynthia Cattell is a space plasma physicist known for her research on solar flares and radiation belts.
James Wynne Dungey (1923–2015) was a British space scientist who was pivotal in establishing the field of space weather and made significant contributions to the fundamental understanding of plasma physics.
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