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

Masakazu Watanabe, George J. Sofko

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10 Citations (Scopus)

Abstract

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
Volume114
Issue number1
DOIs
Publication statusPublished - Jan 1 2009
Externally publishedYes

Fingerprint

interplanetary magnetic fields
Interchanges
magnetic fields
clocks
quadrants
Clocks
convection
arcs
Magnetic fields
magnetic field
aurora
Magnetic flux
lobes
magnetic flux
polar caps
hemispheres
Plasmas
Merging
plasma
reciprocation

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

Cite this

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abstract = "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.",
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AB - 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.

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