Substorm ion injections: Geosynchronous observations and test particle orbits in three-dimensional dynamic MHD fields

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/96JA03032· OSTI ID:544524

Birn, J; Thomsen, M F; Borovsky, J E; Reeves, G D; McComas, D J; Belian, R D ^[1]; Hesse, M ^[2]

---

1. Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
2. NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)

We investigate particle acceleration and the flux increases associated with substorm particle injections using geosynchronous observations and test proton orbits in the dynamic fields of a three-dimensional MHD simulation of neutral line formation and dipolarization in the magnetotail. The energetic particle flux changes obtained from the test particle orbits agree well with observations that demonstrate rapid ion flux increases at energies above {approximately}20keV but little change at lower energies. The {open_quotes}injection region{close_quotes} inferred from the test particles not only has a sharp earthward boundary (the usual injection boundary) but also a sharp but ragged tailward boundary. The earthward portion of enhanced ion flux can be traced to the enhanced cross-tail electric field associated with the collapse and dipolarization of the inner tail, whereas the tailward edge is closely associated with the near-Earth x-type neutral line. Because of the rapid earthward motion of accelerated ions away from the neutral line, this boundary is displaced earthward to where the energetic ions become more adiabatic in the stronger dipolar field. Lower-energy ions are not affected by cross-tail acceleration in the strong E{sub y} fields because their earthward {bold E}{times}{bold B} drift dominates the cross-tail drift, except very close to the neutral line.{copyright} 1997 American Geophysical Union

• OSTI ID: 544524
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A2 Vol. 102; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
EARTH MAGNETOSPHERE
ELECTRIC FIELDS
MAGNETIC STORMS
MAGNETOTAIL
PLASMA ACCELERATION
PLASMA DRIFT
PLASMA SHEET