JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. A3, 10.1029/2001JA900166, 2002
Modeling energetic particle injections in dynamic pulse fields with varying propagation speeds
Demokritus University of Thrace,
Xanthi, Greece
Laboratory for Atmospheric and Space Physics,
Boulder, Colorado, USA
Demokritus University of Thrace,
Xanthi, Greece
Applied Physics Laboratory, Johns Hopkins University,
Laurel, Maryland, USA
Abstract
[1] Dispersionless injections are a ubiquitous characteristic of substorms. They are defined as simultaneous enhancements in the fluxes of electrons and ions of different energies, and they are often observed near or inside geosynchronous orbit. We model dispersionless electron injections by considering the interaction of an earthward propagating electromagnetic pulse with the preexisting electron population. Such simulations have been performed previously [Li et al., 1993, 1998]; however, they assumed a constant propagation velocity for the transient fields. Observations have shown that substorm injections and associated magnetic signatures do not propagate at constant velocities, but rather slow down as they approach the inner magnetosphere. Between 4.5 and 6.6 RE the injection propagation speeds reach surprisingly low values, of the order of 24 km/s. Nonetheless, the injections still remain dispersionless [Reeves et al., 1996]. In our simulation we vary the pulse speed with the radial distance from the Earth to match the reported propagation speeds and demonstrate that dispersionless injections are achievable under such low propagation speeds. In particular, we simulate the dispersionless injections of 12 February 1991 measured at two radially displaced spacecraft (CRRES and LANL 1990–095), when they were both around local midnight.
Received 28 May 2001; revised 14 September 2001; accepted 20 October 2001; published 5 March 2002.
Keywords: dispersionless, injections, modeling.
Index Terms: 2753 Magnetospheric Physics: Numerical modeling; 7807 Space Plasma Physics: Charged particle motion and acceleration; 2744 Magnetospheric Physics: Magnetotail; 2788 Magnetospheric Physics: Storms and substorms.
Citation: Modeling energetic particle injections in dynamic pulse fields with varying propagation speeds, J. Geophys. Res., 107(A3), 10.1029/2001JA900166, 2002.