Influences of IMF By Polarity on Dayside Electron Precipitation in Terms of Energy Channels

Han Wen Shen, Jih Hong Shue, John Dombeck, De Sheng Han

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1 Scopus citations


The By component 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 By polarity 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 By polarity 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 By polarities. 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 By effects on it, which would not have been retrieved without the use of individual energy channels.

Original languageEnglish (US)
Article numbere2021JA030082
JournalJournal of Geophysical Research: Space Physics
Issue number3
StatePublished - Mar 2022
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the grants MOST 109‐2111‐M‐008‐007 and MOST 110‐2111‐M‐008‐010 to National Central University through the Ministry of Science and Technology. We gratefully acknowledge SuperMAG website for using the data of the index. In addition, the authors would like to thank the Editor Natalia Ganushkina and two reviewers for taking the time to evaluate this paper and providing valuable suggestions to improve this paper. SML

Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.


  • IMF by component
  • dayside aurora
  • dayside electron precipitation
  • energy channels
  • hemispheric asymmetry
  • solar wind-magnetosphere-ionosphere coupling


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