Role of interchange reconnection in convection at small interplanetary magnetic field clock angles and in transpolar arc motion

Masakazu Watanabe, George J. Sofko

Research output: Contribution to journalArticle

10 Citations (Scopus)


When the interplanetary magnetic field (IMF) clock angle θC ≡ atan2(BY, BZ) lies in the range 0° < |θC| < 30°, there only persist IMF-lobe and lobe-closed reconnection (both of which we call interchange-type), with Dungey-type reconnection (IMF-closed and lobe-lobe) being absent. Reconnection for IMF BY > 0 (BY < 0) occurs in the northern dusk (dawn) quadrant and in the southern dawn (dusk) quadrant. The IMF-lobe reconnection in one quadrant is coupled to the lobe-closed reconnection in the other quadrant by magnetic flux reciprocation, and in the ionosphere, that reconnection pair produces an "interchange-type merging cell" in the hemisphere of IMF-lobe reconnection and a reciprocal cell in the other hemisphere. When the polar cap is completely divided into two parts by the transpolar plasma sheet (the theta aurora configuration), the interchange-type merging cell transports open magnetic flux from one part of the polar cap to the other without affecting the theta aurora configuration, causing the dawn-dusk motion of the transpolar plasma sheet. This type of flux transport is destroyed if any Dungey-type reconnection occurs. Thus a necessary condition for the theta aurora configuration to be maintained during the dawn-dusk travel of the transpolar plasma sheet is the absence of Dungey-type reconnection. This condition is reasonably satisfied for 0° < |θC| < 30°. The absence of Dungey-type reconnection in the presence of IMF B Y can be understood as a transitional state of the magnetic flux circulation when the IMF rotates from due northward to dawnward or duskward.

Original languageEnglish
Article numberA01209
JournalJournal of Geophysical Research: Space Physics
Issue number1
Publication statusPublished - Jan 1 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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