Fragmented structure of interplanetary type II bursts

Abstract

We present the Ulysses observations of a highly fragmented interplanetary type II burst and an associated pair of forward shocks. We argue that the coupling of Langmuir waves excited by one of these shocks with escaping radiation at the sharp density gradient associated with the companion shock is responsible for the clumpiness of the type II event. This linear coupling process is shown to cause large fluctuations in the efficiency of conversion of Langmuir waves into electromagnetic radiation at the fundamental of the electron plasma frequency f_pe, leading to the fragmentary structure of the type II radio burst.