Type II radio bursts: 2. Application of the new analytic formalism

Abstract

Type II radio bursts drift in frequency as shock waves and coronal mass ejections (CMEs) move through the Sun's corona and the solar wind. This paper applies an extended analytic theoretical model for type II radio bursts to an MHD simulation of the rippled shock front found upstream of the flanks of a CME. The theory treats the acceleration of electrons at the shock, formation of electron beams, growth of Langmuir waves, and conversion of Langmuir energy into radiation. The extended theory is entirely analytic and includes kappa electron velocity distribution functions for the ambient plasma electrons and the shock-reflected electrons. It also includes the plateauing of the electron beam, which releases energy for the Langmuir waves. This paper presents and discusses our numerical results for synthetic radio source regions and synthetic dynamic spectra, gained by applying our radiation model to an MHD simulation of a shock driven by a CME. The investigation reveals strong emission upstream of the flanks of the shock. A complicated rippled shock geometry develops with embedded "ripples" that stimulate short-lived "bright spot" radio sources, which lead to complicated substructures in the dynamic spectrum, and more extended sources that usually have a weaker and more diffuse radio emission. The natural development of ripples on the shock provides a natural link between the ripple theory of Knock, Cairns, and colleagues and the bolt-on model presented here. © 2012 American Geophysical Union. All Rights Reserved.