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A missing variable in solar wind‐magnetosphere‐ionosphere coupling studies
Author(s) -
Sergeev V. A.,
Sormakov D. A.,
Angelopoulos V.
Publication year - 2014
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 - 10.1002/2014gl062271
Subject(s) - plasma sheet , substorm , solar wind , magnetosphere , physics , electrojet , ionosphere , geophysics , atmospheric sciences , plasma , computational physics , magnetic field , earth's magnetic field , quantum mechanics
The auroral electrojet ( AL ) index is commonly used to characterize the magnetospheric activity. The ground magnetic perturbations that comprise AL are formed predominantly by Hall currents, however, and the Hall conductivity is sensitive to plasma sheet T e and N e parameters, which control the production of energetic electrons via their field‐aligned acceleration. Using AL index and nightside‐dawn sector plasma sheet electron data, we demonstrate that a hotter, lower density plasma sheet is associated with stronger ground magnetic variations in the nightside auroral zone than a colder, denser plasma sheet under similar solar wind driving conditions. TheT e 1 / 2 / N e ‐dependent difference may exceed a factor of 4 during the growth phase events, whereas the acceleration during substorm expansions smears it out. Background plasma sheet state is mainly controlled by the solar wind velocity and density. We suggest that plasma sheetT e 1 / 2 / N evariable constitutes an important (and currently ignored) variable in studies of solar wind‐magnetosphere‐ionosphere coupling.