University of Oulu

Pitkänen, T., Hamrin, M., Chong, G. S., & Kullen, A. (2021). Relevance of the north-south electric field component in the propagation of fast convective earthward flows in the magnetotail: An event study. Journal of Geophysical Research: Space Physics, 126, e2021JA029233.

Relevance of the north-south electric field component in the propagation of fast convective earthward flows in the magnetotail : An Event Study

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Author: Pitkänen, T.1,2; Hamrin, M.1; Chong, G. S.1;
Organizations: 1Department of Physics, Umeå University, Umeå, Sweden
2Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
3Department of Space and Plasma Physics, School of Electrical Engineering and Computer Science, Royal Institute of Technology, Stockholm, Sweden
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.5 MB)
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Language: English
Published: American Geophysical Union, 2021
Publish Date: 2021-10-19


Fast earthward plasma flows are commonly observed in the magnetotail plasma sheet. These flows are often termed as bursty bulk flows because of their bursty nature, and they are considered to be generated by magnetic reconnection. Close to the neutral sheet (Bx ∼ 0), the fast flows are considered to be associated with an enhanced dawn-to-dusk electric field (Ey > 0), which together with the northward magnetic field component (Bz > 0) protrude the plasma earthward via enhanced E × B-drift. Sometimes, reversals in the dawn-dusk velocity component perpendicular to the magnetic field (V⊥y) are measured in association with Bx sign changes in the flows. This suggests that the electric field component in the north-south direction (Ez) can play a role in determining the dawn-dusk direction of the enhanced drift. We present data measured by the Magnetospheric Multiscale, which demonstrate that Ez can have a dictating role for V⊥y of fast flows. Furthermore, it is shown that the critical contribution of Ez is not limited only to V⊥y, but it can also dominantly determine the enhanced drift of the fast flows in the X direction (V⊥y). The latter can occur also near and at the neutral sheet, which adds an alternative configuration to the conventional picture of Ey and Bz being the main players in driving the earthward fast flows. The domination of Ez in the studied events appears with potential signatures of an influence of a nonzero dawn-dusk component of the interplanetary magnetic field (IMF By) on the magnetotail.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 126
Issue: 7
Article number: e2021JA029233
DOI: 10.1029/2021JA029233
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work was supported by the Swedish National Space Agency (SNSA) grants 118/17 (T. Pitkänen), 271/14 (M. Hamrin), and 81/17 (G. S. Chong).
Copyright information: © 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.