<論文>1978年12月11日に科学衛星JIKIKEN(EXOS-B)によって観測されたミニサブストームに伴う長周期Pi2磁気脈動(宇宙科学特集号 : 科学衛星JIKIKEN(EXOS-B))

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A typical long-period Pi2 event that was associated with a distinct mini-substorm took place at 1355UT (2255 in 135° east meridian time) on December 11, 1978, after a successive ten-day magnetically calm period. The event was observed simultaneously at both the Jikiken (Exos-B) statellite near an expanded plasmapause on the 21h LT meridian and a ground-based station, Onagawa, on the 〜23h LT meridian. The plasmapause position before the substorm onset is estimated from the stimulated plasma wave experiment to be L≳6.3. A dynamic spectrum analysis of the data revealed that the observed main period of the Pi2 was 140 seconds at Jikiken, and both 140 and 220 seconds at Onagawa. The torsional oscillation model (namely, the plasma-sheet model) that an odd mode hydromagnetic torsional oscillation of the contracted dipole-like field-line that was excited by the distant plasma instability on a tail-like field-line is applied to explain the mechanism of the Pi2. The tail-like field-line whose apex was at > 16.4 R_E is assumed to contract rapidly due to the instability to the dipole-like one with the apex at 9.2 R_E. The period of 140 sec of the same Pi2 event observed at Jikiken is interpreted as a transient hydromagnetic surface wave excited secondarily on the plasmapause. This mechanism is discussed in comparison with the Pg model that a hydromagnetic surface wave on the expanded plasmapause excited by a plasma instability on the plasmapause is observed as a giant pulsation in the auroral zone.
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<論文>1978年12月11日に科学衛星JIKIKEN(EXOS-B)によって観測されたミニサブストームに伴う長周期Pi2磁気脈動(宇宙科学特集号 : 科学衛星JIKIKEN(EXOS-B))

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