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Behavior of the aurora during 10–12 May, 1999 when the solar wind nearly disappeared
Author(s) -
Parks G.,
Brittnacher M.,
Chua D.,
Fillingim M.,
Germany G.,
Spann J.
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 - 10.1029/2000gl000106
Subject(s) - solar wind , atmospheric sciences , interplanetary magnetic field , earth's magnetic field , polar , electron precipitation , precipitation , physics , solar maximum , interplanetary spaceflight , geophysics , environmental science , magnetic field , coronal mass ejection , meteorology , astronomy , magnetosphere , quantum mechanics
The aurora was still active with occasional pseudobreakup events when the solar wind density diminished to unusually small densities (0.2 cc −1 ) during May 10–12, 1999. The aurora was observed at high magnetic latitudes indicating that the electron precipitation source moved northward as the geomagnetic activity decreased. The events we have studied indicate that the solar wind density alone is not the primary parameter that controls the auroral activity. The weak auroral activity was observed with 150 nT magnetic bays and when the interplanetary magnetic field (IMF) B z was small and positive resulting in small ϵ parameter. A new auroral feature was observed on May 11, 1999, between 0900–2000 UT. The electron precipitation was energetic, uniform, and covered the region commonly identified as the polar cap. This precipitation lasted for more than 10 hours and was stable over time scales of tens of minutes. On May 12, as the solar wind began to recover, a prolonged period of dayside activity occurred and was followed by a typical aurora at 0500 UT.