University of Oulu

Holappa, L., & Buzulukova, N. Y. (2022). Explicit IMF By-dependence of energetic protons and the ring current. Geophysical Research Letters, 49, e2022GL098031.

Explicit IMF By-dependence of energetic protons and the ring current

Saved in:
Author: Holappa, Lauri1,2,3; Buzulukova, N. Y.2,3
Organizations: 1Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
2University of Maryland, College Park, MD, USA
3NASA Goddard Space Flight Center, Greenbelt, MD, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1 MB)
Persistent link:
Language: English
Published: American Geophysical Union, 2022
Publish Date: 2022-10-21


The most important parameter driving the solar wind-magnetosphere interaction is the southward (Bz) component of the interplanetary magnetic field (IMF). While the dawn-dusk (By) component of the IMF is also known to play an important role, its effects are usually assumed to be independent of its sign. Here we demonstrate for the first time a seasonally varying, explicit IMF By-dependence of the ring current and Dst index. Using satellite observations and a global magnetohydrodynamic model coupled with a ring current model, we show that for a fixed level of solar wind driving the flux of energetic magnetospheric protons and the growth-rate of the ring current are greater for By < 0 (By > 0) than for By > 0 (By < 0) in Northern Hemisphere summer (winter). While the physical mechanism of this explicit By-effect is not yet fully understood, our results suggest that IMF By modulates magnetospheric convection and plasma transport in the inner magnetosphere.

see all

Series: Geophysical research letters
ISSN: 0094-8276
ISSN-E: 1944-8007
ISSN-L: 0094-8276
Volume: 49
Issue: 8
Article number: e2022GL098031
DOI: 10.1029/2022gl098031
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
114 Physical sciences
Funding: The authors acknowledge the financial support by the Academy of Finland to the Postdoctoral Researcher project of L. Holappa (no. 322459). For N. Y. Buzulukova, this work has been partially supported by NASA Grant 80NSSC19K0085. N. Y. Buzulukova thanks ISSI in Bern Switzerland for support of the International Team N523 “Imaging the Invisible: Unveiling the Global Structure of Earth's Dynamic Magnetosphere.” This work was carried out using the SWMF and BATS-R-US tools developed at the University of Michigan Center for Space Environment Modeling. The modeling tools are part of the Full version of SWMF code that is available for download under a user license through the University of Michigan web-page CIMI model has been developed at NASA GSFC, Heliophysics division, Geospace Physics Laboratory. Computational resources supporting this work were provided by the NASA High-End Computing Program through the NASA Advanced Supercomputing Division at Ames Research Center.
Academy of Finland Grant Number: 322459
Detailed Information: 322459 (Academy of Finland Funding decision)
Dataset Reference: Detailed model settings ( files) and model output used in production of Figures 1 and 2 have been made available online for download at Zenodo ( SWMF run input files are also included in Text S8 and S9 of Supporting Information S1. The solar wind data (solar wind speed and different components of IMF) and the Dst index were downloaded from the OMNI2 database ( All the original POES/MEPED energetic particle data used here are archived in the NOAA/NGDC dataserver (
Copyright information: © 2022 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.