On the role of transition region on the Alfven wave phase mixing in solar spicules

TL;DR

This paper investigates how the transition region affects the dissipation of standing Alfven waves in solar spicules, highlighting the role of phase mixing, density gradients, and magnetic shear in energy transfer to the corona.

Contribution

It introduces a model considering the transition region, steady flow, and sheared magnetic fields to analyze standing Alfven wave damping in solar spicules, which was not extensively studied before.

Findings

Standing Alfven waves dissipate over time, not space.

Density gradients and magnetic shear enhance phase mixing damping.

Damping times align with observed spicule lifetimes.

Abstract

Alfvenic waves are thought to play an important role in coronal heating and solar wind acceleration. Here we investigate the dissipation of standing Alfven waves due to phase mixing at the presence of steady flow and sheared magnetic field in the stratified atmosphere of solar spicules. The transition region between chromosphere and corona has also been considered. The initial flow is assumed to be directed along spicule axis, and the equilibrium magnetic field is taken 2-dimensional and divergence-free. It is determined that in contrast to propagating Alfven waves, standing Alfven waves dissipate in time rather than in space. Density gradients and sheared magnetic fields can enhance damping due to phase mixing. Damping times deduced from our numerical calculations are in good agreement with spicule lifetimes. Since spicules are short living and transient structures, such a fast dissipation mechanism is needed to transport their energy to the corona.