- Title
- Field-Aligned and Ionospheric Currents by AMPERE and SuperMAG During HSS/SIR-Driven Storms
- Creator
- Pedersen, M. N.; Vanhamäki, H.; Aikio, A. T.; Käki, S.; Workayehu, A. B.; Waters, C. L.; Gjerloev, J. W.
- Relation
- Journal of Geophysical Research: Space Physics Vol. 126, Issue 11, no. e2021JA029437
- Publisher Link
- http://dx.doi.org/10.1029/2021JA029437
- Publisher
- Wiley-Blackwell
- Resource Type
- journal article
- Date
- 2021
- Description
- This study considers 28 geomagnetic storms with Dst (Formula presented.) nT driven by high-speed streams (HSSs) and associated stream interaction regions (SIRs) during 2010–2017. Their impact on ionospheric horizontal and field-aligned currents (FACs) have been investigated using superposed epoch analysis of SuperMAG and AMPERE data, respectively. The zero epoch ((Formula presented.)) was set to the onset of the storm main phase. Storms begin in the SIR with enhanced solar wind density and compressed southward oriented magnetic field. The integrated FAC and equivalent currents maximize 40 and 58 min after (Formula presented.), respectively, followed by a small peak in the middle of the main phase ((Formula presented.) + 4 hr), and a slightly larger peak just before the Dst minimum ((Formula presented.) + 5.3 hr). The currents are strongly driven by the solar wind, and the correlation between the Akasofu (Formula presented.) and integrated FAC is 0.90. The number of substorm onsets maximizes near (Formula presented.). The storms were also separated into two groups based on the solar wind dynamic pressure pdyn in the vicinity of the SIR. High pdyn storms reach solar wind velocity maxima earlier and have shorter lead times from the HSS arrival to storm onset compared with low pdyn events. The high pdyn events also have sudden storm commencements, stronger solar wind driving and ionospheric response at (Formula presented.), and are primarily responsible for the first peak in the currents after (Formula presented.). After (Formula presented.) days, the currents and number of substorm onsets become higher for low compared with high pdyn events, which may be related to higher solar wind speed.
- Subject
- storms; currents; solar wind; substorm onsets
- Identifier
- http://hdl.handle.net/1959.13/1435377
- Identifier
- uon:39700
- Identifier
- ISSN:2169-9380
- Language
- eng
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