Analytic modeling of the Moreton wave kinematics

TL;DR

This paper develops an analytical model to understand the kinematics of Moreton waves, comparing different source expansion scenarios with observations, and suggests that flaring region expansion or CME flank expansion better explains the observed waves than the upward CME motion.

Contribution

The paper introduces an analytical model for Moreton wave evolution and demonstrates that flaring or CME flank expansion better explains observed wave kinematics than upward CME motion.

Findings

Model reproduces observed Moreton wave only with impulsive source acceleration.

Upward CME motion alone cannot explain the wave kinematics.

Flaring region or CME flank expansion are likely drivers of Moreton waves.

Abstract

The issue whether Moreton waves are flare-ignited or CME-driven, or a combination of both, is still a matter of debate. We develop an analytical model describing the evolution of a large-amplitude coronal wave emitted by the expansion of a circular source surface in order to mimic the evolution of a Moreton wave. The model results are confronted with observations of a strong Moreton wave observed in association with the X3.8/3B flare/CME event from January 17, 2005. Using different input parameters for the expansion of the source region, either derived from the real CME observations (assuming that the upward moving CME drives the wave), or synthetically generated scenarios (expanding flare region, lateral expansion of the CME flanks), we calculate the kinematics of the associated Moreton wave signature. Those model input parameters are determined which fit the observed Moreton wave kinematics best. Using the measured kinematics of the upward moving CME as the model input, we are not able to reproduce the observed Moreton wave kinematics. The observations of the Moreton wave can be reproduced only by applying a strong and impulsive acceleration for the source region expansion acting in a piston mechanism scenario. Based on these results we propose that the expansion of the flaring region or the lateral expansion of the CME flanks is more likely the driver of the Moreton wave than the upward moving CME front.