Characteristics of transient magnetic field events in the dayside magnetosphere
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概要
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Transient magnetic field variations in the dayside magnetosphere, whose magnetic signatures resemble the flux transfer events (FTE's), are statistically investigated by using AMPTE/CCE magnetometer data during 1984-1986. These transient magnetic field events are observed in the L=6.0-9.4 and 0700-1600 magnetic local time (MLT) sector. It is found that the detection rate and the magnitude of magnetic field perturbation increase as the distance from the magnetopause decreases, which suggests that the transient magnetic field events are the phenomena near the magnetopause. In northern latitudes the radial component of the magnetic field shows a positive perturbation followed by a negative perturbation, while in southern latitudes the reversed sequence is seen. This tendency is the same as FTE's. Examination of the simultaneously obtained IMP-8 and ISEE-1 magnetic field data indicates that the transient magnetic field events occur mainly in association with southward orientation of the interplanetary magnetic field (IMF). This tendency is also the same as FTE's. These similarities in statistical characteristics suggest that the transient magnetic field events are caused by the same generation mechanism as FTE's. One of the interesting features revealed in this study is the MLT-dependence of the rotational polarity of the transverse magnetic field perturbation. The rotation is predominantly left-handed (with respect to the ambient magnetic field) in the forenoon sector, while it is right-handed in the afternoon sector. This suggests that the source of the magnetic field perturbation, presumably located near the magnetopause, moves azimuthally tailward.
- 国立極地研究所の論文
著者
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Kokubun Susumu
Geophysics Research Laboratory The University Of Tokyo
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Kawano Hideaki
Geophysics Research Laboratory University Of Tokyo
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Takahashi Kazue
The Johns Hopkins University Applied Physics Laboratory
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