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Supersubstorms (SML < −2500 nT): Magnetic storm and solar cycle dependences
Author(s) -
Hajra Rajkumar,
Tsurutani Bruce T.,
Echer Ezequiel,
Gonzalez Walter D.,
Gjerloev Jesper W.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja021835
Subject(s) - solar cycle 23 , solar cycle 22 , solar wind , interplanetary magnetic field , physics , geomagnetic storm , interplanetary spaceflight , solar cycle , solar cycle 24 , magnetosphere , atmospheric sciences , earth's magnetic field , astrophysics , magnetic field , plasma , nuclear physics , quantum mechanics
We study extremely intense substorms with SuperMAG AL (SML) peak intensities < −2500 nT (“supersubstorms”/SSSs) for the period from 1981 to 2012. The SSS events were often found to be isolated SML peaks and not statistical fluctuations of the indices. The SSSs occur during all phases of the solar cycle with the highest occurrence (3.8 year −1 ) in the descending phase. The SSSs exhibited an annual variation with equinoctial maximum altering between spring in solar cycle 22 and fall in solar cycle 23. The occurrence rate and strength of the SSSs did not show any strong relationship with the intensity of the associated geomagnetic storms. All SSS events were associated with strong southward interplanetary magnetic field B s component. The B s fields were part of interplanetary magnetic clouds in 46% and of interplanetary sheath fields in 54% of the cases. About 77% of the SSSs were associated with small regions of very high density solar wind plasma parcels or pressure pulses impinging upon the magnetosphere. Comments on how SSS events may cause power outages at Earth are discussed at the end of the paper.