Field‐aligned current during an interval of B Y ‐dominated interplanetary‐field; modeled‐to‐observed comparisons

J. A. Carter*, A. A. Samsonov, S. E. Milan, G. Branduardi‐Raymont, A. J. Ridley, L. J. Paxton, B. J. Anderson, C. L. Waters, T. Edwards

*Corresponding author for this work

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We model an interval of remarkable interplanetary magnetic field, for which we have a comprehensive set of observational data. This interval is associated with the arrival of an interplanetary coronal mass ejection. The solar wind densities at the time are particularly high and the interplanetary magnetic field is primarily northward over many hours. This results in strong auroral emissions within the polar cap in a cusp spot, which we associate with lobe reconnection at the high-latitude magnetopause. We also observe areas of upwards field-aligned current within the summer Northern Hemisphere polar cap that exhibit large current magnitudes. The model is able to reproduce the spatial distribution of the field-aligned currents well, even under changing conditions in the incoming interplanetary magnetic field. Discrepancies exist between the modeled and observed current magnitudes. Notably, the winter Southern Hemisphere exhibits much lower current magnitudes overall. We also model a sharp transition of the location of magnetopause reconnection at the beginning of the interval, before the IMF remained northward for many hours. The reconnection location changed rapidly from a subsolar location at the low-latitude magnetopause under southward interplanetary magnetic field conditions, to a high-latitude lobe reconnection location when the field is northward. This occurs during a fast rotation of the IMF at the shock front of a magnetic cloud
Original languageEnglish
Article numbere2021JA029722
JournalJournal of Geophysical Research: Space Physics
Number of pages15
Publication statusPublished - 2021


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