Solar Particle Access into the Inner Magnetosphere

Abstract

There are four modes of access of energetic particles into the inner magnetosphere, defined here as the region of ‘closed’ field lines, i.e. regions of latitude below, for instance, the 40 keV electron boundary. These are direct entry to all latitudes above the cut-off, longitudinal drift from the nightside to the dayside pseudotrapping region, radial diffusion through the dayside magnetopause and a combination of radial and pitch angle diffusion. The first two modes of access are reversible processes, and the access boundaries can, in principle at least, be determined using numerical calculations in static model magnetospheric fields.

Apart from this static description of particle access, it is also possible to use energetic solar particle measurements on closed field lines as diagnostics for magnetospheric motions and wave distribution as function of time and location within the magnetosphere, and information can be obtained on the motion of boundaries and the strength of pitch angle scattering as function of position within the magnetosphere and as function of geomagnetic activity. Observations and theoretical treatments of these problems are discussed.