Plasma Flows and Bubble Properties Associated with the Magnetic Dipolarization in Space Close to Geosynchronous Orbit

• Published in: Journal of astronomy and space sciences Vol. 30; no. 2; pp. 95 - 100
• Main Authors: Lee, Ji-Hee, Lee, Dae-Young, Park, Mi-Young, Lee, Eun-Hee
• Format: Journal Article
• Language: English
• Published: 한국우주과학회 01.06.2013; The Korean Space Science Society
• Subjects: magnetic dipolarization; plasma bubbles; substorm; 천문학; plasma bubbles; magnetic dipolarization; substorm
• ISSN: 2093-5587; 2093-1409
• DOI: 10.5140/JASS.2013.30.2.095

In this paper we examine a total of 16 dipolarization events that were observed by THEMIS spacecraft in space close togeosynchronous orbit, r < ~ 7 RE. For the identified events, we examine the characteristics of the plasma flows and associatedbubbles as defined based on pV5/3, where p is the plasma pressure and V the volume of unit magnetic flux. First, we find thatthe flow speed in the near-geosynchronous region is very low, mostly within a few tens of km/s, except for a very few events forwhich the flow can rise up to ~200 km/s but only very near the dipolarization onset time. Second, the bubble parameter, pV5/3,decreases by a much smaller factor after the dipolarization onset than for the events in the farther out tail region. We suggestthat the magnetic dipolarization in the near-geosynchronous region generates or is associated with only very weak plasmabubbles. Such bubbles in the near-geosynchronous region would penetrate earthward only by a small distance before theystop at an equilibrium position or drift around the Earth.