Active auroral arc powered by accelerated electrons from very high altitudes
Abstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite...
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2021-01-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-020-79665-5 |
| _version_ | 1818722622197727232 |
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| author | Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori |
| author_facet | Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori |
| author_sort | Shun Imajo |
| collection | DOAJ |
| description | Abstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30,000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms. |
| first_indexed | 2024-12-17T20:57:33Z |
| format | Article |
| id | doaj.art-d14d902323da45109a1842312ec18a2b |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-12-17T20:57:33Z |
| publishDate | 2021-01-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-d14d902323da45109a1842312ec18a2b2022-12-21T21:32:50ZengNature PortfolioScientific Reports2045-23222021-01-011111810.1038/s41598-020-79665-5Active auroral arc powered by accelerated electrons from very high altitudesShun Imajo0Yoshizumi Miyoshi1Yoichi Kazama2Kazushi Asamura3Iku Shinohara4Kazuo Shiokawa5Yoshiya Kasahara6Yasumasa Kasaba7Ayako Matsuoka8Shiang-Yu Wang9Sunny W. Y. Tam10Tzu‑Fang Chang11Bo‑Jhou Wang12Vassilis Angelopoulos13Chae-Woo Jun14Masafumi Shoji15Satoko Nakamura16Masahiro Kitahara17Mariko Teramoto18Satoshi Kurita19Tomoaki Hori20Institute for Space-Earth Environmental Research, Nagoya UniversityInstitute for Space-Earth Environmental Research, Nagoya UniversityAcademia Sinica Institute of Astronomy and AstrophysicsInstitute of Space and Astronautical Science, Japan Aerospace Exploration AgencyInstitute of Space and Astronautical Science, Japan Aerospace Exploration AgencyInstitute for Space-Earth Environmental Research, Nagoya UniversityGraduate School of Natural Science and Technology, Kanazawa UniversityPlanetary Plasma and Atmospheric Research Center, Tohoku UniversityData Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto UniversityAcademia Sinica Institute of Astronomy and AstrophysicsInstitute of Space and Plasma Sciences, National Cheng Kung UniversityInstitute of Space and Plasma Sciences, National Cheng Kung UniversityAcademia Sinica Institute of Astronomy and AstrophysicsDepartment of Earth, Planetary, and Space Sciences, University of CaliforniaInstitute for Space-Earth Environmental Research, Nagoya UniversityInstitute for Space-Earth Environmental Research, Nagoya UniversityInstitute for Space-Earth Environmental Research, Nagoya UniversityInstitute for Space-Earth Environmental Research, Nagoya UniversityFaculty of Engineering, Kyushu Institute of TechnologyResearch Institute for Sustainable Humanosphere, Kyoto UniversityInstitute for Space-Earth Environmental Research, Nagoya UniversityAbstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30,000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms.https://doi.org/10.1038/s41598-020-79665-5 |
| spellingShingle | Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori Active auroral arc powered by accelerated electrons from very high altitudes Scientific Reports |
| title | Active auroral arc powered by accelerated electrons from very high altitudes |
| title_full | Active auroral arc powered by accelerated electrons from very high altitudes |
| title_fullStr | Active auroral arc powered by accelerated electrons from very high altitudes |
| title_full_unstemmed | Active auroral arc powered by accelerated electrons from very high altitudes |
| title_short | Active auroral arc powered by accelerated electrons from very high altitudes |
| title_sort | active auroral arc powered by accelerated electrons from very high altitudes |
| url | https://doi.org/10.1038/s41598-020-79665-5 |
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