Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 33, 519-524, 2015
https://doi.org/10.5194/angeo-33-519-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
ANGEO Communicates
06 May 2015
Extremely intense (SML ≤–2500 nT) substorms: isolated events that are externally triggered?
B. T. Tsurutani1, R. Hajra2, E. Echer2, and J. W. Gjerloev3,4 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
2Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, SP, Brazil
3Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
4Birkeland Center, University of Bergen, Norway
Abstract. We examine particularly intense substorms (SML ≤–2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst ≤–250 nT) and intense (−100 nT ≥ Dst >–250) magnetic storms. SSS events can also occur during nonstorm (Dst ≥–50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm−3) solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

Citation: Tsurutani, B. T., Hajra, R., Echer, E., and Gjerloev, J. W.: Extremely intense (SML ≤–2500 nT) substorms: isolated events that are externally triggered?, Ann. Geophys., 33, 519-524, https://doi.org/10.5194/angeo-33-519-2015, 2015.
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Short summary
Particularly intense substorms (SSS), brilliant auroral displays with strong >106A currents in the ionosphere, are studied. It is believed that these SSS events cause power outages during magnetic storms. It is shown that SSS events can occur during all intensity magnetic storms; thus power problems are not necessarily restricted to the rare most intense storms. We show four SSS events that are triggered by solar wind pressure pulses. If this is typical, ~30-minute warnings could be issued.
Particularly intense substorms (SSS), brilliant auroral displays with strong 106A currents in...
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