Coronal Heating by MHD Waves

Abstract

The heating of the solar chromosphere and corona to the observed high temperatures, imply the presence of ongoing heating that balances the strong radiative and thermal conduction losses expected in the solar atmosphere. It has been theorized for decades that the required heating mechanisms of the chromospheric and coronal parts of the active regions, quiet-Sun, and coronal holes are associated with the solar magnetic fields. However, the exact physical process that transport and dissipate the magnetic energy which ultimately leads to the solar plasma heating are not yet fully understood. The current understanding of coronal heating relies on two main mechanism: reconnection and MHD waves that may have various degrees of importance in different coronal regions. In this review we focus on recent advances in our understanding of MHD wave heating mechanisms. First, we focus on giving an overview of observational results, where we show that different wave modes have been discovered in the corona in the last decade, many of which are associated with a significant energy flux, either generated in situ or pumped from the lower solar atmosphere. Afterwards, we summarise the recent findings of numerical modelling of waves, motivated by the observational results. Despite the advances, only 3D MHD models with Alfvén wave heating in an unstructured corona can explain the observed coronal temperatures compatible with the quiet Sun, while 3D MHD wave heating models including cross-field density structuring are not yet able to account for the heating of coronal loops in active regions to their observed temperature.

Chromospheric heating and generation of plasma outflows by impulsively generated two-fluid magnetoacoustic waves

“…The present mechanisms considered for solar coronal heating are essentially based on magnetic field reconnection and resonant dissipation and/or phase-mixing of magnetohydrodynamic (MHD) waves. The later mechanism was reviewed recently by Van Doorsselaere et al (2020). who showed that various wave modes may contribute to the heating of the solar corona.…”

Transverse Loop Oscillations via Vortex Shedding: A Self-oscillating Process

“…In recent years, observations by the Coronal Multi-channel Polarimeter, the Solar Dynamics Observatory, and Hinode spacecraft have already proven the ubiquity of transverse perturbations and waves in magnetic structures in the solar corona (e.g., Tomczyk et al 2007;McIntosh et al 2011). The importance of these waves and oscillations is connected to their use in coronal seismology (e.g., Nakariakov & Ofman 2001;Nakariakov & Verwichte 2005), as well as their potential role as heating mechanisms for the solar corona (for a review, see Van Doorsselaere et al 2020).…”

Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

“…There have been several reviews that discuss the key observations and theoretical developments on MHD waves in the solar chromosphere and corona and their contribution to heating (e.g., Arregui, 2015; Aschwanden, 2019; Jess et al., 2015; Mathioudakis et al., 2013; Narain & Ulmschneider, 1996; Van Doorsselaere et al., 2020; Zaqarashvili & Erdélyi, 2009). In the present review, we aim to discuss the physics of MHD waves and instabilities in the chromospheric plasma, and their heating capabilities.…”