Interplanetary scattering of fast solar electrons deduced from type III bursts observed at low frequencies

Abstract

Observations of low frequency solar type III radio bursts and the associated fast solar electrons show that the total path length traveled by the particles between the Sun and the Earth is significantly greater than the length of the smooth Archimedean spiral trajectory followed by the centroid of the type III exciter (Alvarez et al. , 1975). Here we assume that the ratio of electron path length and the spiral length increases approximately as r n , where r is heliocentric distance, and then compute the radio bursts arrival time at 1 AU for different values of n . A comparison with the radio observations indicates that the best fit occurs for n = 1.5 ± 1.0. We interpret these results in terms of the variation of electron scattering with heliocentric distance.