Mid-Tail Ion Dynamics at Substorm Onset

  1. Joseph R. Kan,
  2. Thomas A. Potemra,
  3. Susumu Kokubun and
  4. Takesi Iijima
  1. D. C. Delcourt

Published Online: 19 MAR 2013

DOI: 10.1029/GM064p0225

Magnetospheric Substorms

Magnetospheric Substorms

How to Cite

Delcourt, D. C. (1991) Mid-Tail Ion Dynamics at Substorm Onset, in Magnetospheric Substorms (eds J. R. Kan, T. A. Potemra, S. Kokubun and T. Iijima), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM064p0225

Author Information

  1. Space Science Laboratory, NASA/MSFC, Hunstville, Alabama 35812

Publication History

  1. Published Online: 19 MAR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875900308

Online ISBN: 9781118663981



  • Magnetospheric substorms—Congresses


Features of ion trajectories during transient “tail-like” to “dipole-like” reconfigurations of the geomagnetic field are investigated by means of three-dimensional single particle codes. It is shown that the large electric fields induced by the collapse of the geomagnetic tail result in rapid injections of the mid-tail (∼10–15 RE ) populations into low L shells. During this transport, the computations demonstrate a possible transient violation of the particle adiabatic invariants due to local field variations on the time scale of the gyro-period. This effect, which depends upon the particle charge-to-mass ratio, can yield intense (up to the hundreds of kilo-electron volt range) ion accelerations and pitch angle variations. The circulation of terrestrial outflows is further examined within this process, and it is shown that the cleft ion fountain is a potential plasma source for the storm-time ring current. The high-latitude upflowing polar wind also appears of particular interest in this context, since it yields dense and energetic proton shells in inner magnetospheric regions. A detailed analysis of the trajectory results furthermore reveals a clear earthward boundary for the newly-created energetic populations, which corresponds to the post-dipolarization location of the ion adiabatic-nonadiabatic separatrix in the geomagnetic tail.