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Observations of centrifugal acceleration during compression of magnetosphere
Author(s) -
Cladis J. B.,
Collin H. L.,
Lennartsson O. W.,
Moore T. E.,
Peterson W. K.,
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 - 10.1029/1999gl010737
Subject(s) - physics , magnetosphere , acceleration , particle acceleration , plasma , ionosphere , computational physics , magnetic field , polar , magnetosphere particle motion , geophysics , mechanics , classical mechanics , astronomy , nuclear physics , quantum mechanics
Centrifugal acceleration of escaping ionospheric plasma is one of the important and fundamental processes responsible for energizing and transporting ionospheric plasma to all regions of the magnetosphere. Normally this mechanism operates over extremely large distances. Because of this feature and limitations in particle instrumentation, it has not been possible to directly confirm from in‐situ plasma measurements the very specific predictions made by basic plasma theory about centrifugal acceleration. We report here data obtained near Polar satellite apogee over the northern polar cap during a magnetospheric compression event that occurred on September 24, 1998. Between 2345:18 and 2347:18 UT the magnetic field rotated by about 20° and increased in intensity. The Toroidal Imaging Mass‐Angle Spectrograph (TIMAS) instrument on Polar obtained bulk velocity moments of preexisting upflowing H + , O + , He + , and He ++ ions with enough precision and resolution to directly demonstrate, together with computer simulation, that the magnitude and direction of changes in plasma motion during this event follow directly from the changes in the magnetic field configuration as predicted by the equations describing centrifugal acceleration.