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Relations Between v z and B x Components in Solar Wind and their Effect on Substorm Onset
Author(s) -
Kubyshkina Marina,
Semenov Vladimir,
Erkaev Nikolay,
Gordeev Evgeny,
Dubyagin Stepan,
Ganushkitalia,
Shukhtina Maria
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl076268
Subject(s) - substorm , physics , interplanetary magnetic field , sign (mathematics) , solar wind , plasma sheet , astrophysics , asymmetry , magnetosphere , magnetic field , geophysics , plasma , nuclear physics , mathematical analysis , mathematics , quantum mechanics
We analyze two substorm onset lists, produced by different methods, and show that the ( B x · v z ) product of the solar wind (SW) velocity and interplanetary magnetic field (IMF) components for two thirds of all substorm onsets has the same sign as IMF B z . The explanation we suggest is the efficient displacement of the magnetospheric plasma sheet due to IMF B x and SW flow v z , which both force the plasma sheet moving in one direction if the sign of ( B x · v z ) correlates with the sign B z . The displacement of the current sheet, in its turn, increases the asymmetry of the magnetotail and can alter the threshold of substorm instabilities. We study the SW and IMF data for the 15‐year period (which comprises two substorm lists periods and the whole solar cycle) and reveal the similar asymmetry in the SW, so that the sign of ( B x · v z ) coincides with the sign of IMF B z during about two thirds of all the time. This disproportion can be explained if we admit that about 66% of IMF B z component is transported to the Earth's orbit by the Alfvén waves with antisunward velocities.