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Solar Wind-Magnetosphere Coupling During High-Intensity Long-Duration Continuous AE Activity (HILDCAA)

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posted on 2024-01-09, 15:03 authored by SE Milan, MK Mooney, G Bower, AL Fleetham, SK Vines, J Gjerloev
High-Intensity Long-Duration Continuous AE Activity (HILDCAA) intervals are driven by High Speed solar wind Streams (HSSs) during which the rapidly-varying interplanetary magnetic field (IMF) produces high but intermittent dayside reconnection rates. This results in several days of large, quasi-periodic enhancements in the auroral electrojet (AE) index. There has been debate over whether the enhancements in AE are produced by substorms or whether HILDCAAs represent a distinct class of magnetospheric dynamics. We investigate 16 HILDCAA events using the expanding/contracting polar cap model as a framework to understand the magnetospheric dynamics occurring during HSSs. Each HILDCAA onset shows variations in open magnetic flux, dayside and nightside reconnection rates, the cross-polar cap potential, and AL that are characteristic of substorms. The enhancements in AE are produced by activity in the pre-midnight sector, which is the typical substorm onset region. The periodicities present in the intermittent IMF determine the exact nature of the activity, producing a range of behaviors from a sequence of isolated substorms, through substorms which merge into one-another, to almost continuous geomagnetic activity. The magnitude of magnetic fluctuations, dB/dt, in the pre-midnight sector during HSSs is sufficient to produce a significant risk of Geomagnetically Induced Currents.

Funding

A Consolidated Grant Proposal for Solar and Planetary Science at the University of Leicester, 2022 - 2025

Science and Technology Facilities Council

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Investigating the Drivers of Geomagnetically Induced Currents

Natural Environment Research Council

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History

Citation

Milan, S. E., Mooney, M. K., Bower, G., Fleetham, A. L., Vines, S. K., & Gjerloev, J. (2023). Solar wind-magnetosphere coupling during High-Intensity Long-Duration Continuous AE Activity (HILDCAA). Journal of Geophysical Research: Space Physics, 128, e2023JA032027. https://doi.org/10.1029/2023JA032027

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Space Physics

Volume

128

Issue

11

Publisher

American Geophysical Union (AGU)

issn

2169-9380

eissn

2169-9402

Acceptance date

2023-11-02

Copyright date

2023

Available date

2024-01-09

Language

en

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