Particle observations by EPA/EPONA during the outbound pass of Giotto from comet Halley and their relationship to large scale magnetic field irregularities.
Neubauer, F. M.; Ip, W. -H.; Daly, P.; Wenzel, K. P.; Kirsch, E.; O'Sullivan, D.; Thompson, A.; McKenna-Lawlor, S.
Germany, Ireland
Abstract
The acceleration processes producing spikes seen superimposed on the general intensity time profile of energetic particles obtained with EPA/EPONA during the outbound pass of Giotto on 14/15 March 1986, are studied using complementary magnetic field data. Three different types of spikes were identified. Evidence for the ion pick-up process and probably also for field line reconnection as well as for the shock drift process combined with the first order Fermi mechanism was found near to the bowshock. At distances >1×106km from the bowshock generally the second order Fermi effect contributed to the observed particle energies. The anisotropy in particle count rate detected during the inbound and outbound passes suggests a preferential escape of particles from the outbound bowshock.