Type II radio emission predictions: Multiple shock ripples and dynamic spectra

Abstract

A recently developed model of type II radio emission from a single ripple on a global shock is extended to (1) investigate the interaction of multiple shock ripples and (2) calculate the dynamic spectra of radio emission for a shock that consists of multiple independent ripples, as it propagates from. 10 solar radii to 1 AU. It is found that the interaction of ripples is relatively unimportant, typically changing the predicted emission level by only 20%. It is predicted that dynamic spectra vary with observer location, which implies that different spacecraft observing the same type II event will see different dynamic spectra. Correlations between source location and dynamic spectra predicted for remote observers are thus investigated and a number of characteristic type II features, such as split bands, are found to be produced naturally by a combination of different source locations and propagation effects such as frequency blocking. The results imply a need for large-scale structure such, as large-scale fluctuations in magnetic field orientations, coronal mass ejections, and corotating interaction regions in order to account for the diversity in type II burst observations. Copyright 2003 by the American Geophysical Union.