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Simultaneous THEMIS in situ and auroral observations of a small substorm

Research output: Contribution to journalJournal article


  • E. Donovan
  • W. Liu
  • J. Liang
  • E. Spanswick
  • I. Voronkov
  • M. Conners
  • M. Syrjasuo
  • G. Baker
  • B. Jackel
  • T. Trondsen
  • M. Greffen
  • V. Angelopoulos
  • C.T. Russell
  • S.B. Mende
  • H.U. Frey
  • A. Keiling
  • C.W. Carlson
  • J.P. McFadden
  • K.-H. Glassmeier
  • U. Auster
  • K. Hayashi
  • K. Sakaguchi
  • K. Shiokawa
  • I.J. Rae
Article numberL17S18
Journal publication date12/08/2008
JournalGeophysical Research Letters
Number of pages5
Original languageEnglish


We present ground-based and in situ observations from March 13, 2007. The THEMIS satellites were in the evening sector conjugate to THEMIS ground-based imagers. At ∼0507 UT there was an optical onset on inner CPS field lines. This involved near-simultaneous brightening of 1 MLT hour longitudinal segment of the onset arc. The part of the arc that brightened was that closest to the equatorward boundary of the diffuse (proton) aurora. Within one minute, a dipolarization front moved across four THEMIS satellites. Based on their locations, the order in which they detected the dipolarization front, and the auroral evolution, we assert that the expansion phase began earthward of the four satellites and evolved radially outwards. We conclude that this onset occurred in an azimuthally localized region of highly stretched field lines.

Bibliographic note

Copyright 2008 by the American Geophysical Union