Velocity Distributions of Ion Beams in the Plasma Sheet Boundary Layer

  1. Tom Chang,
  2. M. K. Hudson,
  3. J. R. Jasperse,
  4. R. G. Johnson,
  5. P. M. Kintner and
  6. M. Schulz
  1. T. E. Eastman,
  2. R. J. Decoster and
  3. L. A. Frank

Published Online: 21 MAR 2013

DOI: 10.1029/GM038p0117

Ion Acceleration in the Magnetosphere and Ionosphere

Ion Acceleration in the Magnetosphere and Ionosphere

How to Cite

Eastman, T. E., Decoster, R. J. and Frank, L. A. (2013) Velocity Distributions of Ion Beams in the Plasma Sheet Boundary Layer, 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/GM038p0117

Author Information

  1. Department of Physics and Astronomy, the University Of Iowa, Iowa City, Iowa 52242

Publication History

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

ISBN Information

Print ISBN: 9780875900636

Online ISBN: 9781118664216

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Keywords:

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

Summary

Field-aligned ion beams commonly occur in the plasma sheet boundary layer. With sufficient energy and angular resolution, plasma measurements of ion beam velocity distributions there can be used as a diagnostic tool to evaluate ion acceleration processes. Model fits to data are shown for adiabatic deformation of a flowing Maxwellian, acceleration due to field-aligned potentials, and current-sheet acceleration. Isodensity contours of the velocity distributions typically show a closer spacing within the low-energy portion of the ion beams that is not consistent with adiabatic deformation alone acting upon an initially isotropic distribution function. Detailed comparisons of acceleration models with the overall shapes of the observed beam distributions indicate that the ion beams have been subjected to some potential drop which may be field-aligned (DeCoster and Frank, 1979) or perhaps cross-tail as for the current-sheet acceleration process (Lyons and Speiser, 1982). Measurements of velocity dispersion effects have also proven to be a useful diagnostic tool although propagation effects are difficult to separate from signatures of the initial acceleration process. Ion acceleration processes in the magnetotail are primarily associated with the plasma sheet boundary layer. This observational result has important implications for magnetotail dynamics.