Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock
The generation of energetic particles in the Universe is an important topic in astrophysical and space physics. Although the diffusive shock acceleration has been acknowledged to play an essential role in particle acceleration, the injection problem has not been well resolved yet. Using measurements...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ada5f0 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832585008323231744 |
|---|---|
| author | Y. Y. Liu J. B. Cao C. M. Liu Y. T. Song D. K. Hu |
| author_facet | Y. Y. Liu J. B. Cao C. M. Liu Y. T. Song D. K. Hu |
| author_sort | Y. Y. Liu |
| collection | DOAJ |
| description | The generation of energetic particles in the Universe is an important topic in astrophysical and space physics. Although the diffusive shock acceleration has been acknowledged to play an essential role in particle acceleration, the injection problem has not been well resolved yet. Using measurements from the Magnetospheric Multiscale spacecraft, we report unexpected spiky enhancements of energetic electron flux in the upstream region of the Earth’s bow shock. Such enhancements are then demonstrated to result from the accelerated electron population by shock reflection. Meanwhile, the magnetic field exhibits no variations except an increase in radius of curvature. Based on the results above, we uncover the underlying acceleration scenario. When the interplanetary magnetic field with a proper curvature approaches the bow shock, the two ends of a magnetic field line may touch the shock front earlier than its middle part. Magnetic mirror points form at the two field-line-shock intersections. The solar wind electrons are therefore trapped and bounce between two mirror points. Eventually, these electrons undergo fast Fermi reflection several times and gain substantial energies. The spacecraft observation of accelerated electrons is reproduced with a numerical method based on the reflection model. Such an acceleration process may be a potential solution to the injection problem. |
| format | Article |
| id | doaj-art-913d778bedfa48ffb557f40c7093911d |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-913d778bedfa48ffb557f40c7093911d2025-01-27T07:10:52ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979217910.3847/1538-4357/ada5f0Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow ShockY. Y. Liu0https://orcid.org/0000-0002-0765-1709J. B. Cao1C. M. Liu2https://orcid.org/0000-0002-9705-5387Y. T. Song3D. K. Hu4School of Space and Earth Sciences, Beihang University , Beijing 100191, People’s Republic of China ; jbcao@buaa.edu.cn; Key Laboratory of Space Environment Monitoring and Information Processing , Ministry of Industry and Information Technology, Beijing 100191, People’s Republic of ChinaSchool of Space and Earth Sciences, Beihang University , Beijing 100191, People’s Republic of China ; jbcao@buaa.edu.cn; Key Laboratory of Space Environment Monitoring and Information Processing , Ministry of Industry and Information Technology, Beijing 100191, People’s Republic of ChinaSchool of Space and Earth Sciences, Beihang University , Beijing 100191, People’s Republic of China ; jbcao@buaa.edu.cn; Key Laboratory of Space Environment Monitoring and Information Processing , Ministry of Industry and Information Technology, Beijing 100191, People’s Republic of ChinaSchool of Space and Earth Sciences, Beihang University , Beijing 100191, People’s Republic of China ; jbcao@buaa.edu.cn; Key Laboratory of Space Environment Monitoring and Information Processing , Ministry of Industry and Information Technology, Beijing 100191, People’s Republic of ChinaSchool of Space and Earth Sciences, Beihang University , Beijing 100191, People’s Republic of China ; jbcao@buaa.edu.cn; Key Laboratory of Space Environment Monitoring and Information Processing , Ministry of Industry and Information Technology, Beijing 100191, People’s Republic of ChinaThe generation of energetic particles in the Universe is an important topic in astrophysical and space physics. Although the diffusive shock acceleration has been acknowledged to play an essential role in particle acceleration, the injection problem has not been well resolved yet. Using measurements from the Magnetospheric Multiscale spacecraft, we report unexpected spiky enhancements of energetic electron flux in the upstream region of the Earth’s bow shock. Such enhancements are then demonstrated to result from the accelerated electron population by shock reflection. Meanwhile, the magnetic field exhibits no variations except an increase in radius of curvature. Based on the results above, we uncover the underlying acceleration scenario. When the interplanetary magnetic field with a proper curvature approaches the bow shock, the two ends of a magnetic field line may touch the shock front earlier than its middle part. Magnetic mirror points form at the two field-line-shock intersections. The solar wind electrons are therefore trapped and bounce between two mirror points. Eventually, these electrons undergo fast Fermi reflection several times and gain substantial energies. The spacecraft observation of accelerated electrons is reproduced with a numerical method based on the reflection model. Such an acceleration process may be a potential solution to the injection problem.https://doi.org/10.3847/1538-4357/ada5f0Interplanetary particle accelerationPlanetary bow shocksShocksSolar wind |
| spellingShingle | Y. Y. Liu J. B. Cao C. M. Liu Y. T. Song D. K. Hu Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock The Astrophysical Journal Interplanetary particle acceleration Planetary bow shocks Shocks Solar wind |
| title | Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock |
| title_full | Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock |
| title_fullStr | Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock |
| title_full_unstemmed | Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock |
| title_short | Electron Acceleration by Multiple Fast Fermi Reflections at Earth’s Bow Shock |
| title_sort | electron acceleration by multiple fast fermi reflections at earth s bow shock |
| topic | Interplanetary particle acceleration Planetary bow shocks Shocks Solar wind |
| url | https://doi.org/10.3847/1538-4357/ada5f0 |
| work_keys_str_mv | AT yyliu electronaccelerationbymultiplefastfermireflectionsatearthsbowshock AT jbcao electronaccelerationbymultiplefastfermireflectionsatearthsbowshock AT cmliu electronaccelerationbymultiplefastfermireflectionsatearthsbowshock AT ytsong electronaccelerationbymultiplefastfermireflectionsatearthsbowshock AT dkhu electronaccelerationbymultiplefastfermireflectionsatearthsbowshock |