Journal of Astronomy and Space Sciences

The Korean Space Science Society (한국우주과학회)
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Plasma Flows and Bubble Properties Associated with the Magnetic Dipolarization in Space Close to Geosynchronous Orbit

  • Lee, Ji-Hee (Department of Astronomy and Space Science Chungbuk National University) ;
  • Lee, Dae-Young (Department of Astronomy and Space Science Chungbuk National University) ;
  • Park, Mi-Young (Department of Astronomy and Space Science Chungbuk National University) ;
  • Lee, Eun-Hee (Yonsei University Observatory, Yonsei University)
  • Received : 2013.03.12
  • Accepted : 2013.04.04
  • Published : 2013.06.15
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Abstract

In this paper we examine a total of 16 dipolarization events that were observed by THEMIS spacecraft in space close to geosynchronous orbit, r < ${\sim}7\;R_E$. For the identified events, we examine the characteristics of the plasma flows and associated bubbles as defined based on $pV^{5/3}$, where p is the plasma pressure and V the volume of unit magnetic flux. First, we find that the flow speed in the near-geosynchronous region is very low, mostly within a few tens of km/s, except for a very few events for which the flow can rise up to ~200 km/s but only very near the dipolarization onset time. Second, the bubble parameter, $pV^{5/3}$, decreases by a much smaller factor after the dipolarization onset than for the events in the farther out tail region. We suggest that the magnetic dipolarization in the near-geosynchronous region generates or is associated with only very weak plasma bubbles. Such bubbles in the near-geosynchronous region would penetrate earthward only by a small distance before they stop at an equilibrium position or drift around the Earth.

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References

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