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Abstract Extreme (>20 nT/s) geomagnetic disturbances (GMDs, also denoted as MPEs—magnetic perturbation events)—impulsive nighttime disturbances with time scale ∼5–10 min, have sufficient amplitude to cause bursts of geomagnetically induced currents (GICs) that can damage technical infrastructure. In this study, we present occurrence statistics for extreme GMD events from five stations in the MACCS and AUTUMNX magnetometer arrays in Arctic Canada at magnetic latitudes ranging from 65° to 75°. We report all large (≥6 nT/s) and extreme GMDs from these stations from 2011 through 2022 to analyze variations of GMD activity over a full solar cycle and compare them to those found in three earlier studies. GMD activity between 2011 and 2022 did not closely follow the sunspot cycle, but instead was lowest during its rising phase and maximum (2011–2014) and highest during the early declining phase (2015–2017). Most of these GMDs, especially the most extreme, were associated with high‐speed solar wind streams (Vsw >600 km/s) and steady solar wind pressure. All extreme GMDs occurred within 80 min after substorm onsets, but few within 5 min. Multistation data often revealed a poleward progression of GMDs, consistent with a tailward retreat of the magnetotail reconnection region. These observations indicate that extreme GIC hazard conditions can occur for a variety of solar wind drivers and geomagnetic conditions, not only for fast‐coronal mass ejection driven storms.
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This content will become publicly available on December 1, 2026
Properties of Earthward and Tailward High‐Speed Plasma Flows in Earth's Distant Magnetotail: Solar Cycle and Geomagnetic Activity Dependence
Abstract High‐speed plasma flows in Earth's magnetotail are important for the global dynamics of the magnetosphere. We survey 11 yrs of high‐speed plasma flows observed by the ARTEMIS spacecraft in Earth's distant magnetotail between XGSE = −52 REand XGSE = −66 REto investigate their properties for a wide range of solar and geomagnetic activity levels. We find that tailward and earthward high‐speed flows at these distances exhibit notable asymmetries, with higher ion temperatures and larger dawn‐dusk magnetic field magnitudes in tailward flows compared to earthward flows. These asymmetries suggest that a significant portion of tailward high‐speed flows originate from near‐Earth magnetotail reconnection, while earthward high‐speed flows originate from a distant magnetotail reconnection site tailward of ARTEMIS. The occurrence rate of high‐speed flows follows the solar cycle progression and is about twice as high during solar maximum compared to solar minimum. Furthermore, both tailward and earthward high‐speed flows have higher median ion and electron temperatures, outflow speeds, and dawn‐dusk magnetic fields during solar maximum. In addition to the solar cycle dependence, the ion and electron temperatures in the high‐speed flows increase with increasing geomagnetic activity, for both the Auroral Electrojet (AE) and the Disturbance Storm Time (Dst) indices. Interestingly, during large substorms (AE > 1,100 nT) and geomagnetic storms (Dst < −90 nT), only tailward high‐speed flows are observed at lunar distances in this data set. In essence, our results indicate that the properties of both near‐Earth and distant tail reconnection are functions of the solar cycle and geomagnetic activity.
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- Award ID(s):
- 2409449
- PAR ID:
- 10681125
- Publisher / Repository:
- Journal of Geophysical Research - Space Physics
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 130
- Issue:
- 12
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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