Impulsive Ion Acceleration in Earth's Outer Magnetosphere

  1. Tom Chang,
  2. M. K. Hudson,
  3. J. R. Jasperse,
  4. R. G. Johnson,
  5. P. M. Kintner and
  6. M. Schulz
  1. D. N. Baker and
  2. R. D. Belian

Published Online: 21 MAR 2013

DOI: 10.1029/GM038p0375

Ion Acceleration in the Magnetosphere and Ionosphere

Ion Acceleration in the Magnetosphere and Ionosphere

How to Cite

Baker, D. N. and Belian, R. D. (1986) Impulsive Ion Acceleration in Earth's Outer Magnetosphere, in Ion Acceleration in the Magnetosphere and Ionosphere (eds T. Chang, M. K. Hudson, J. R. Jasperse, R. G. Johnson, P. M. Kintner and M. Schulz), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM038p0375

Author Information

  1. University of California, Los Alamos National Laboratory, Los Alamos, NM 87545

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1986

ISBN Information

Print ISBN: 9780875900636

Online ISBN: 9781118664216



  • Magnetosphere—Congresses;
  • Ionosphere—Congresses;
  • Ion flow dynamics—Congresses;
  • Space plasmas—Congresses


Considerable observational evidence is found that ions are accelerated to high energies in the outer magnetosphere during geomagnetic disturbances. The acceleration often appears to be quite impulsive causing temporally brief (tens of seconds), very intense bursts of ions in the distant plasma sheet as well as in the near-tail region. These ion bursts extend in energy from tens of keV to over 1 MeV and are closely associated with substorm expansive phase onsets. Although the very energetic ions are not of dominant importance for magnetotail plasma dynamics, they serve as an important tracer population. Their absolute intensity and brief temporal appearance bespeaks a strong and rapid acceleration process in the near-tail, very probably involving large induced electric fields substantially greater than those associated with cross-tail potential drops. Subsequent to their impulsive acceleration, these ions are injected into the outer trapping regions forming ion “driftecho” events, as well as streaming tailward away from their acceleration site in the near-earth plasma sheet. Most auroral ion acceleration processes occur (or are greatly enhanced) during the time that these global magnetospheric events are occurring in the magnetotail. A qualitative model relating energetic ion populations to near tail magnetic reconnection at substorm onset followed by global redistribution is quite successful in explaining the primary observational features. Recent measurements of the elemental composition and charge-states have proven valuable for showing the source (solar wind or ionosphere) of the original plasma population from which the ions were accelerated. New data relying on such methods hold great promise for illuminating the details of the substorm ion acceleration mechanism.