Propagation of Alfv\'enic Waves From Corona to Chromosphere and Consequences for Solar Flares

TL;DR

This study models how Alfvén waves propagate from the corona to the chromosphere, revealing their potential role in heating, electron acceleration, and sunquake excitation during solar flares.

Contribution

Developed a 2-fluid model to simulate Alfvén wave transmission and damping in the solar atmosphere, highlighting the impact of wave frequency on energy transfer and chromospheric heating.

Findings

Energy transmission can exceed 20% for waves with periods ≤1 second.

Waves with periods ≥10 seconds pass through with minimal damping.

Significant damping (37%-100%) occurs for waves with periods ≤1 second due to ion-neutral friction.

Abstract

How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a 2-fluid model (of plasma and neutrals) and used it to perform 1D simulations of Alfv\'en waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra and umbra) show that energy transmission from corona to chromosphere can exceed 20% of incident energy for wave periods of one second or less. Damping of waves in the chromosphere depends strongly on wave frequency: waves with periods 10 seconds or longer pass through the chromosphere with relatively little damping, however, for periods of 1 second or less, a substantial fraction (37%-100%) of wave energy entering the chromosphere is damped by ion-neutral friction in the mid and upper chromosphere, with electron resistivity playing some role in the lower chromosphere and in umbras. We therefore conclude that Alfv\'enic waves with periods of a few seconds or less are capable of heating the chromosphere during solar flares, and speculate that they could also contribute to electron acceleration or exciting sunquakes.