Observation and modeling of compressional Pi 3 magnetic pulsations

Journal Article · Sat Jul 01 04:00:00 EDT 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA03368· OSTI ID:223567

Matsuoka, H; Takahashi, K; Yumoto, K ^[1]

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1. Nagoya Univ., Toyokawa (Japan); and others

Compressional magnetic pulsations with irregular waveforms and periods longer than 150 s (here termed Pi 3) have been studied by using data from Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) and GOES 5 and 6 in the dayside magnetosphere and compared with signatures on the ground at low latitudes by using data from Kakioka station (L=1.25). On the ground, the pulsations appear in the horizontal component. A study of 17 such concurrent events during a 2-month period in 1986 reveals following pulsation characteristics. (1) The peak-to-peak amplitudes in space ({delta}B{sub T}) and on the ground ({delta}H) are comparable and are in the range of 0.5-7 nT. (2) On the ground the pulsations can be seen at all local times, even at midnight, while at geostationary orbit they are observed only on the dayside with a clear amplitude maximum at noon. (3) The pulsations on the ground lag those observed by CCE near local noon, and the lag increases as the local time separation between CCE and the ground station increases. The time lag is 1-2 min longer when the ground station is on the nightside then when it is on the dayside. (4) The time lag between pulsations observed at geostationary orbit and near noon by CCE varies systematically with local time and is about 2 min per 6 hours of local time separation. These observations indicate that some nightside pulsations in the Pi 3 band have dayside origins. The position dependence of the pulsation amplitude can be explained well by changes in the magnetopause current, which are in turn presumably caused by changes in the solar wind dynamic pressure. The time lags observed in space are consistent with signal propagation in the MHD fast mode, but the variation in space-ground time lags with ground station local time must be attributed to another mechanism. 39 refs., 13 figs., 1 tab.

• OSTI ID: 223567
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A7 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
EARTH MAGNETOSPHERE
GROUND LEVEL
LONG WAVE RADIATION
MAGNETIC FIELDS
MILLI HZ RANGE
PULSATIONS
REMOTE SENSING
SATELLITES
WAVE PROPAGATION