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Explicit IMF B y Dependence in Geomagnetic Activity: Modulation of Precipitating Electrons
Author(s) -
Holappa L.,
Asikainen T.,
Mursula K.
Publication year - 2020
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 - 10.1029/2019gl086676
Subject(s) - earth's magnetic field , solar wind , physics , interplanetary magnetic field , electrojet , geophysics , northern hemisphere , magnetosphere , ionosphere , atmospheric sciences , flux (metallurgy) , ionospheric dynamo region , magnetic field , materials science , quantum mechanics , metallurgy
The most important driver of geomagnetic activity is the north–south ( B z ) component of the interplanetary magnetic field (IMF), which dominates the solar wind‐magnetosphere coupling and all solar wind coupling functions. While the east–west ( B y ) IMF component is also included in most coupling functions, its effect is always assumed to be symmetric with respect of its sign. However, recent studies have shown that, for a fixed value of any coupling function, geomagnetic activity is stronger forB y > 0 than forB y < 0 in Northern Hemisphere winter. In Southern Hemisphere winter, the dependence on theB ysign is reversed. In this paper, we use measurements of National Oceanic and Atmospheric Administration Polar‐Orbiting Operational Environmental Satellites to show that the flux of magnetospheric electrons precipitating into the atmosphere also exhibits an explicitB ydependence. ThisB ydependence is strong in the midnight and dawn sectors where it causes a relatedB yeffect in the westward electrojet and geomagnetic activity by modulating ionospheric conductivity.