Abstract We present results of a study of the diffusion coefficient for low-energy protons upstream of three interplanetary shocks observed on ISEE-3. The intensity increase as the shock approaches can be fitted by a running exponential, the e-folding time t★ of which is assumed to be a direct measure of the diffusion coefficient. The energy dependence of t★ close to the shock (0–60 Re) is derived from the four energy channels covering the range 35–238 keV. The t★ in the low energy channels (less than 100 keV) increases with distance away from the shock. However t★ decreases above 100 keV and roughly beyond 100 Re, so that the diffusion coefficient becomes independent of energy. We suggest that the energy-independence of t★ in a region well upstream of the shock is the result of enhanced parallel scattering through 90° pitch-angles for higher energy (larger gyroradius) particles which are more sensitive to variations in the transverse direction of the magnetic field.
Diffusion coefficients of low-energy protons upstream of quasi-parallel interplanetary shocks
Advances in Space Research ; 4 , 2-3 ; 315-318
1984-01-01
4 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
NTRS | 1986
|Elsevier | 1986
|