The wave properties of coronal bright fronts observed using SDO/AIA

Abstract

Coronal bright fronts (CBFs) are large scale wavefronts that propagate though the solar corona at hundreds of kilometers per second. While their kinemat- ics have been studied in detail, many questions remain regarding the temporal evolution of their amplitude and pulse width. Here, contemporaneous high ca- dence, multi-thermal observations of the solar corona from the Solar Dynamic Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO) spacecraft are used to determine the kinematics and expansion rate of a CBF wavefront observed on 2010 August 14. The CBF was found to have a lower initial velocity with weaker deceleration in STEREO observations compared to SDO (~340 km s?1 and ?72 m s?2 as opposed to ~410 km s?1 and ?279 m s?2). The CBF kinematics from SDO were found to be highly passband-dependent, with an initial velocity ranging from 379?12 km s?1 to 460?28 km s?1 and accel- eration ranging from ?128?28 m s?2 to ?431?86 m s?2 in the 335 ?A and 304 ?A passbands respectively. These kinematics were used to estimate a quiet coronal magnetic field strength range of ~1?2 G. Significant pulse broadening was also observed, with expansion rates of ~130 km s?1 (STEREO) and ~220 km s?1 (SDO). By treating the CBF as a linear superposition of sinusoidal waves within a Gaussian envelope, the resulting dispersion rate of the pulse was found to be ~8?13 Mm2 s?1. These results are indicative of a fast-mode magnetoacoustic wave pulse propagating through an inhomogeneous medium.