Magnetospheric Parameters Determined from Structured Micropulsations

摘要

The structured elements in Pc 1 and Pi 1 events display characteristics of multihop and halfhop ULF whistlers respectively. Analysis of these events which is carried out for different magnetic field and plasma distribution models yields useful information about the source and propagation of these micropulsations as well as information about the magnetospheric plasma distribution. The Pc 1 propagation zone is centered about 75 degrees geomagnetic latitude on the sunlit hemisphere, and about 65 degrees on the dark hemisphere. Equatorial plasma densities are in general agreement with those determined from VLF whistler analysis and satellite observations. Evidence for spikes and steep gradients in the plasma density is presented. The region for propagation of structured Pi 1 elements is located between seven and thirteen earth radii at solar magnetospheric longitudes of approximately 135 degrees. The difference between the structured Pc 1 and Pi 1 elements is discussed in terms of hypothetical sources and of the magnetospheric wave amplification by trapped particles in the ion-cyclotron resonance interaction. (Author)