The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons
Abstract Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>...
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| Format: | Article |
| Language: | English |
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Wiley
2016-07-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1002/2016GL069029 |
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| author | J. Yu L.Y. Li J. B. Cao G. D. Reeves D. N. Baker H. Spence |
| author_facet | J. Yu L.Y. Li J. B. Cao G. D. Reeves D. N. Baker H. Spence |
| author_sort | J. Yu |
| collection | DOAJ |
| description | Abstract Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (Bz‐IMF < −2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00–18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancake distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher‐energy electrons have stronger pancake distributions (the larger A), suggesting that the compression‐induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00–06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day‐night asymmetry and the interplanetary conditions. The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. These variations are consistent with the drift shell splitting and/or magnetopause shadowing effect. |
| format | Article |
| id | doaj-art-37fc56599bdf4e37a8c0445fa02c4dce |
| institution | Kabale University |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2016-07-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-37fc56599bdf4e37a8c0445fa02c4dce2025-08-20T03:49:41ZengWileyGeophysical Research Letters0094-82761944-80072016-07-0143147319732710.1002/2016GL069029The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electronsJ. Yu0L.Y. Li1J. B. Cao2G. D. Reeves3D. N. Baker4H. Spence5School of Space and Environment Beihang University Beijing ChinaSchool of Space and Environment Beihang University Beijing ChinaSchool of Space and Environment Beihang University Beijing ChinaSpace Sciences and Applications Group Los Alamos National Laboratory Los Alamos New Mexico USALaboratory for Atmospheric and Space Physics University of Colorado Boulder Boulder Colorado USAInstitue for the Study of Earth, Oceans, and Space University of New Hampshire Durham New Hampshire USAAbstract Using the Van Allen Probe in situ measured magnetic field and electron data, we examine the solar wind dynamic pressure and interplanetary magnetic field (IMF) effects on global magnetic field and outer radiation belt relativistic electrons (≥1.8 MeV). The dynamic pressure enhancements (>2 nPa) cause the dayside magnetic field increase and the nightside magnetic field reduction, whereas the large southward IMFs (Bz‐IMF < −2nT) mainly lead to the decrease of the nightside magnetic field. In the dayside increased magnetic field region (magnetic local time (MLT) ~ 06:00–18:00, and L > 4), the pitch angles of relativistic electrons are mainly pancake distributions with a flux peak around 90° (corresponding anisotropic index A > 0.1), and the higher‐energy electrons have stronger pancake distributions (the larger A), suggesting that the compression‐induced betatron accelerations enhance the dayside pancake distributions. However, in the nighttime decreased magnetic field region (MLT ~ 18:00–06:00, and L ≥ 5), the pitch angles of relativistic electrons become butterfly distributions with two flux peaks around 45° and 135° (A < 0). The spatial range of the nighttime butterfly distributions is almost independent of the relativistic electron energy, but it depends on the magnetic field day‐night asymmetry and the interplanetary conditions. The dynamic pressure enhancements can make the nighttime butterfly distribution extend inward. The large southward IMFs can also lead to the azimuthal expansion of the nighttime butterfly distributions. These variations are consistent with the drift shell splitting and/or magnetopause shadowing effect.https://doi.org/10.1002/2016GL069029solar wind dynamic pressuresouthward interplanetary magnetic fieldday‐night asymmetrical variations of magnetic fieldday‐night asymmetrical variations of relativistic electron pitch angle distributionspancake distributionsbutterfly distributions |
| spellingShingle | J. Yu L.Y. Li J. B. Cao G. D. Reeves D. N. Baker H. Spence The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons Geophysical Research Letters solar wind dynamic pressure southward interplanetary magnetic field day‐night asymmetrical variations of magnetic field day‐night asymmetrical variations of relativistic electron pitch angle distributions pancake distributions butterfly distributions |
| title | The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| title_full | The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| title_fullStr | The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| title_full_unstemmed | The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| title_short | The influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| title_sort | influences of solar wind pressure and interplanetary magnetic field on global magnetic field and outer radiation belt electrons |
| topic | solar wind dynamic pressure southward interplanetary magnetic field day‐night asymmetrical variations of magnetic field day‐night asymmetrical variations of relativistic electron pitch angle distributions pancake distributions butterfly distributions |
| url | https://doi.org/10.1002/2016GL069029 |
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