Plasma observations of magnetopause crossings at geosynchronous orbit
- Los Alamos National Laboratory, NM (United States)
The entire three-spacecraft magnetospheric plasma analyzer (MPA) data set has been examined for intervals of magnetosheath plasma at geosynchronous orbit. Over the 6 1/2 spacecraft years of data reviewed, 916 5-min intervals of magnetosheath plasma observations were identified and cataloged. Unlike previous studies that suggested that magnetopause encounters were far more likely on the prenoon that postnoon side at geosynchronous orbit, this study examines three independent lines of evidence and finds that only a small asymmetry (in this same sense) exists. On a statistical basis, a local time of {approximately}1130 is both the median and mean for these magnetosheath observations; this local time is simply consistent with the effects of an aberrated solar wind direction due to the motion of the Earth around the Sun. Simultaneous multipoint observations across both sides of local noon are also consistent with a small offset due to aberration of the magnetopause. Finally, the authors examined the locations of the dawn-dusk flow reversals for a number of cases where one of the geosynchronous spacecraft was outside the magnetopause in the magnetosheath flow. These flow reversals tended to occur near local noon, again indicating that in contrast to previous findings, no large asymmetry exists. 16 refs., 6 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 106835
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A11 Vol. 99; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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