Energy spectrum of low-energy fluxes of particles accelerated by interplanetary shocks

Abstract

The injection rate of particles at the front of interplanetary shocks has usually been studied locally, around the shock passage by the observer's position, but little is known of how the efficiency of the particle-acceleration process evolves as the shock propagates from the Sun to the Earth. In many events accelerated particles are observed long in advance of the arrival of the shock (from 5 hours to 2 days), and they show large anisotropies. We have used a compound shock-particle model to derive the injection rate of particles at the shock front and their energy spectrum, as a function of time, by fitting the observed particle fluxes and anisotropies between 100 and 1000 keV. We have studied three individual low-energy particle events taken as representatives of West, Central Meridian and East events.