University of Oulu

Holappa, L., Reistad, J. P., Ohma, A., Gabrielse, C., & Sur, D. (2021). The magnitude of imf b y influences the magnetotail response to solar wind forcing. Journal of Geophysical Research: Space Physics, 126(11).

The magnitude of IMF By influences the magnetotail response to solar wind forcing

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Author: Holappa, L.1,2,3; Robinson, R. M.2,3; Pulkkinen, A.3;
Organizations: 1Space Climate Research Group, Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
2Catholic University of America, Washington, DC, USA
3NASA Goddard Space Flight Center, Greenbelt, MD, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.2 MB)
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Language: English
Published: American Geophysical Union, 2021
Publish Date: 2022-04-21


The dynamics of substorms are known to be dominated by the North-South (Bz) component of the Interplanetary Magnetic Field (IMF), which is the most important driver of the dayside reconnection. Even though the dawn-dusk (By) component is also known to play a role in substorm dynamics, its effects are not yet fully understood. In this paper we study how IMF By modulates the onset latitude, strength and occurrence frequency of substorms as well as the isotropic boundary (IB) latitude of energetic protons. We show that the substorm onset latitude and the IB latitude are about one degree lower for large magnitude By (|By| < 3nT) than for small By. In contrast, the substorm occurrence frequency is larger for small |By|. We suggest that the magnetotail is more stable during large |By|, requiring the magnetotail lobes (and hence the polar cap) to contain more flux to initiate a substorm compared to the situation when By is small.

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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: 11
Article number: e2021JA029752
DOI: 10.1029/2021JA029752
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work of Lauri Holappa was funded by the Academy of Finland Postdoctoral project (no. 322459). Anders Ohma was supported by the Research Council of Norway/CoE under contract 223252/F50. Jone Peter Reistad was funded by the Research Council of Norway through grant 300844/F50. This effort was facilitated by the Center for the Unified Study of Interhemispheric Asymmetries (CUSIA), NASA Award 80NSSC20K0606. Christine Gabrielse was funded by NASA Award 80NSSC20K0606.
Academy of Finland Grant Number: 322459
Detailed Information: 322459 (Academy of Finland Funding decision)
Copyright information: © 2021. American Geophysical Union.