Periodical
Influences of IMF ByPolarity on Dayside Electron Precipitation in Terms of Energy Channels
| العنوان: | Influences of IMF ByPolarity on Dayside Electron Precipitation in Terms of Energy Channels |
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| المؤلفون: | Shen, Han‐Wen, Shue, Jih‐Hong, Dombeck, John, Han, De‐Sheng |
| المصدر: | Journal of Geophysical Research - Space Physics; March 2022, Vol. 127 Issue: 3 |
| مستخلص: | The Bycomponent of the interplanetary magnetic field (IMF) has long been suggested to play a crucial role in modulating precipitating electrons that create the dayside aurora. However, the effects of the Bypolarity on dayside precipitating electrons have never been examined in terms of energy channels. The present study statistically analyzes these effects using number fluxes of four energy channels. Our results show that the flux response of the dayside electron precipitation to the Bypolarity is not fixed in different energy channels. We infer that the response in the energy range of 688–1,000 eV is associated with interhemispheric field‐aligned currents, while the response in the energy range of 154–224 eV is likely related to the direct entry of magnetosheath electrons via antiparallel reconnection. In addition, local time distributions of precipitating electrons reveal two types of preexisting hemispheric asymmetry regardless of the Bypolarities. The first (second) type, which appears in the 06–12 magnetic local time (MLT) (12–18 MLT) sector, indicates higher (lower) flux in the Southern Hemisphere than in the Northern Hemisphere. All of the present results improve our understanding at the dayside aurora and the IMF Byeffects on it, which would not have been retrieved without the use of individual energy channels. The dawn‐dusk component (By) of the interplanetary magnetic field (IMF) usually leads to a hemispheric asymmetry in aurora. As has long been known, the aurora is created by precipitating electrons. Auroral features are often manifested from combined effects of precipitating electrons with different energies. Different from the simple use of auroral images, we reexamine the IMF Byeffects on the dayside aurora using number fluxes of precipitating electrons in four energy channels. The results reveal that the response to the Bypolarity for the energy range of 154–224 eV likely results from the direct entry of magnetosheath electrons modulated by antiparallel reconnection. The interhemispheric field‐aligned currents induced by IMF Bymainly impact on the features of the energy range of 688–1,000 eV. Aside from the effects caused by the Bypolarity, two types of hemispheric asymmetry in the spatial distribution of the dayside electron precipitation already existed in the prenoon (06–12 magnetic local time [MLT]) and postnoon (12–18 MLT) sectors respectively. The prenoon (postnoon) type shows higher (lower) flux in the Southern Hemisphere than in the Northern Hemisphere. From perspective of precipitating electrons in different energy channels, this study provides us new insights into the hemispheric asymmetry of dayside aurora. The interplanetary magnetic field Byeffects on dayside auroras are firstly examined from perspective of energy channels of precipitating electronsTwo types of preexisting hemispheric asymmetry in the dayside electron precipitation are found to be unrelated to the BypolarityThe response of the dayside electron precipitation to the Bypolarity is found to depend on the energy channel The interplanetary magnetic field Byeffects on dayside auroras are firstly examined from perspective of energy channels of precipitating electrons Two types of preexisting hemispheric asymmetry in the dayside electron precipitation are found to be unrelated to the Bypolarity The response of the dayside electron precipitation to the Bypolarity is found to depend on the energy channel |
| قاعدة البيانات: | Supplemental Index |
| تدمد: | 21699380 21699402 |
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| DOI: | 10.1029/2021JA030082 |