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Response of the equatorial and polar magnetosphere to the very tenuous solar wind on May 11, 1999
Author(s) -
Farrugia C. J.,
Singer H. J.,
Evans D.,
Berdichevsky D.,
Scudder J. D.,
Ogilvie K. W.,
Fitzenreiter R. J.,
Russell C. T.
Publication year - 2000
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 - 10.1029/2000gl003800
Subject(s) - magnetosphere , solar wind , polar , atmospheric sciences , physics , substorm , northern hemisphere , geophysics , asymmetry , interplanetary magnetic field , southern hemisphere , geology , astronomy , magnetic field , quantum mechanics
We examine effects in the equatorial and polar magnetosphere during 9–13 May, 1999. Earth's field at geostationary orbit became closely dipolar for ∼16 hours when solar wind densities n sw were <1 cm −3 . Electron precipitation in the northern polar cap intensified as n sw decreased, with significant fluxes up to ∼15 keV energy on May 11. The simultaneous precipitation void in the southern polar cap implies a very pronounced north‐south asymmetry, also reflected in the hemispherical power deposition. With an intense and collimated strahl, these observations support the ideas of Fairfield and Scudder [1985] on the preferential entry of the strahl into the northern hemisphere under the observed IMF away sector as a source of the north‐south precipitation asymmetry. The polar rain north‐south asymmetry argues against an ejecta source for the solar wind drop‐out. The temporal profiles of solar wind parameters were very asymmetric with respect to the time of minimum n sw , and strong compressions and substorm activity prevailed as n sw recovered.