Coronal Extreme Ultraviolet (EUV) Waves and Their Seismological Applications

Abstract:

Magnetohydrodynamic (MHD) waves can be used as seismological tools to probe the physical conditions of the solar corona, including its magnetic field and plasma parameters. Recent high cadence and full-disk imaging observations in extreme ultraviolet (EUV) by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) have opened a new chapter in understanding these waves and utilizing them for coronal seismology. We will review such new observations, focusing on two intimately related phenomena - global EUV waves (so-called "EIT waves") associated with coronal mass ejections (CMEs) and quasi-periodic, fast-mode magnetosonic wave trains associated with flares: (1) The generation and propagation of global EUV waves and their interaction with coronal structures, e.g., reflection and refraction, can provide diagnostics for the global corona in which they propagate, such as mapping the spatial distribution of the wave phase speed and thus the magnetic field strength. (2) AIA-detected fast-mode wave trains are closely correlated with flare pulsations seen from radio to hard X-rays and propagate at typically 500-2000 km/s along funnel-shaped waveguides often located within CME bubbles. They can provide diagnostics for flare energy release mechanisms and the local corona around the flaring active region. We will discuss the roles of such waves in energy transport within the solar atmosphere and in their associated CME/flare eruptions.