South‐North hemispheric asymmetry of the FAE distribution around the cusp egion: cluster observation

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Title: South‐North hemispheric asymmetry of the FAE distribution around the cusp egion: cluster observation
Authors: Shi, J
Zhang, Z
Torkar, K
Cheng, Z
Escoubet, P
Farzakeley, A
Dunlop, M
Carr, C
Item Type: Journal Article
Abstract: Cluster data from late July to early October were used to study the distribution of field‐aligned electron (FAE) events around the two cusps. An FAE event was defined as electron parallel flux >3 × 108 (cm2 s)−1. The total number of FAE events around the two cusps was basically identical, but downward FAE events prevailed in the south and upward FAE events in the north. In the southern cusp, the peak of the FAE events distribution versus altitude was about 1.3 RE higher and the peak of the FAE events distribution versus invariant latitude (ILAT) was about 4° ILAT lower. Only the downward FAEs around the southern cusp had a second ILAT peak, which was located about 11° higher than the main peak. The normalized number of FAEs showed nearly the same features as the unnormalized number of the FAEs events. These results indicated a north‐south asymmetry of the FAE distribution around the two cusps. Some causes for the asymmetry are discussed, the main ones being the asymmetry of the magnetospheric configuration resulting from geomagnetic dipolar tilt and solar wind flows, the interplanetary magnetic field asymmetry related to the magnetosphere, and the difference of ionospheric conductivity in the two hemispheres. Various solar wind‐magnetosphere interaction processes, such as quasi‐viscous interaction and reconnection, are responsible for the asymmetry, too. The second distribution peak (at higher ILAT) of the downward FAE events around the southern cusp corresponded to high solar wind speed and may be associated with the northward interplanetary magnetic field Bz field‐aligned current at low altitude. This requires further studies, however.
Issue Date: 1-Jan-2019
Date of Acceptance: 21-Jun-2019
URI: http://hdl.handle.net/10044/1/72058
DOI: https://doi.org/10.1029/2019JA026582
ISSN: 2169-9380
Publisher: American Geophysical Union (AGU)
Start Page: 1
End Page: 11
Journal / Book Title: Journal of Geophysical Research: Space Physics
Copyright Statement: ©2019. American Geophysical Union. All Rights Reserved. This is the peer reviewed version of the following article: Shi, J., Zhang, Z., Torkar, K., Cheng, Z., Escoubet, P., Farzakeley, A., et al ( 2019). South‐north hemispheric asymmetry of the FAE distribution around the cusp region: Cluster observation. Journal of Geophysical Research: Space Physics, 124., which has been published in final form at https://doi.org/10.1029/2019JA026582. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
Sponsor/Funder: Particle Physics and Astronomy Research Council (PPARC)
European Space Agency / Estec
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Funder's Grant Number: PPA/G/O/2001/00023
RES/PSS/NR/bc/337/2004
PPA/R/S/1999/00488
PP/E001076/1
ST/H00419X/1
ST/G008272/1
ST/I000623/1
ST/J004553/1
ST/K001051/1
ST/L001276/1
ST/M003116/1
ST/N002784/1
ST/P003427/1
ST/T000260/1
Publication Status: Published online
Article Number: 2019JA026582
Online Publication Date: 2019-07-16
Appears in Collections:Space and Atmospheric Physics
Physics



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