A Hydrodynamic Model of Alfv\'enic Wave Heating in a Coronal Loop and its Chromospheric Footpoints

TL;DR

This study models Alfvénic wave propagation and dissipation in coronal loops, revealing how travel times and plasma ionization influence energy deposition and chromospheric heating, advancing understanding of wave-based coronal heating mechanisms.

Contribution

It introduces a ray tracing method for wave propagation in hydrodynamic simulations, removing the instant propagation assumption and analyzing its effects on loop dynamics.

Findings

Ionization level critically affects wave dissipation location and rate.

Long-duration waves penetrate deeper into the chromosphere, creating a pressure front.

Wave dissipation drives a pressure front propagating deeper, unlike electron beam heating.

Abstract

Alfv\'enic waves have been proposed as an important energy transport mechanism in coronal loops, capable of delivering energy to both the corona and chromosphere and giving rise to many observed features, of flaring and quiescent regions. In previous work, we established that resistive dissipation of waves (ambipolar diffusion) can drive strong chromospheric heating and evaporation, capable of producing flaring signatures. However, that model was based on a simplified assumption that the waves propagate instantly to the chromosphere, an assumption which the current work removes. Via a ray tracing method, we have implemented traveling waves in a field-aligned hydrodynamic simulation that dissipate locally as they propagate along the field line. We compare this method to and validate against the magnetohydrodynamics code Lare3D. We then examine the importance of travel times to the dynamics of the loop evolution, finding that (1) the ionization level of the plasma plays a critical role in determining the location and rate at which waves dissipate; (2) long duration waves effectively bore a hole into the chromosphere, allowing subsequent waves to penetrate deeper than previously expected, unlike an electron beam whose energy deposition rises in height as evaporation reduces the mean-free paths of the electrons; (3) the dissipation of these waves drives a pressure front that propagates to deeper depths, unlike energy deposition by an electron beam.