The dependence of the EIT wave velocity on the magnetic field strength

TL;DR

This study investigates the relationship between EIT wave velocity and magnetic field strength, finding a negative correlation that challenges the fast-mode wave model and supports the fieldline stretching explanation.

Contribution

It provides observational evidence linking EIT wave speed to magnetic field strength, favoring the fieldline stretching model over the fast-mode wave hypothesis.

Findings

EIT wave velocity negatively correlates with magnetic field strength.

Results challenge the fast-mode wave model predictions.

Supports the fieldline stretching model as explanation.

Abstract

"EIT waves" are a wavelike phenomenon propagating in the corona, which were initially observed in the extreme ultraviolet (EUV) wavelength by the EUV Imaging Telescope (EIT). Their nature is still elusive, with the debate between fast-mode wave model and non-wave model. In order to distinguish between these models, we investigate the relation between the EIT wave velocity and the local magnetic field in the corona. It is found that the two parameters show significant negative correlation in most of the EIT wave fronts, {\it i.e.}, EIT wave propagates more slowly in the regions of stronger magnetic field. Such a result poses a big challenge to the fast-mode wave model, which would predict a strong positive correlation between the two parameters. However, it is demonstrated that such a result can be explained by the fieldline stretching model, \emph{i.e.,} that "EIT waves" are apparently-propagating brightenings, which are generated by successive stretching of closed magnetic field lines pushed by the erupting flux rope during coronal mass ejections (CMEs).