Uniturbulence and Alfven wave solar model

TL;DR

This paper develops a new solar atmospheric model that incorporates kink wave damping to improve understanding of solar wind acceleration and coronal heating, extending previous models by including additional wave modes and non-linear effects.

Contribution

It introduces the UAWSOM model, combining kink wave energy evolution with MHD equations, capturing non-linear damping effects and providing a framework for multi-wave mode solar wind modeling.

Findings

Kink wave energy evolution contains non-linear damping terms.

Numerical simulations show kink wave driving causes solar wind outflow.

The model offers a pathway to improve solar wind and coronal heating theories.

Abstract

AWSOM-type models (Van der Holst et al. 2014) have been very successful in describing the solar atmosphere by incorporating the Alfven wave driving as extra contributions in the global MHD equations. However, they lack the contributions from other wave modes. In this paper, we aim to write governing equations for the energy evolution equation of kink waves. In a similar manner as AWSOM, we combine the kink wave evolution equation with MHD. Our goal is to incorporate the extra heating provided by the uniturbulent damping of the kink waves. We attempt to construct the UAWSOM equations (uniturbulence and Alfven wave driven solar models). We have recently described the MHD equations in terms of the Q-variables. These latter variables allow to follow the evolution of waves in a co-propagating reference frame. We transform the Q-variable MHD equations into an energy evolution equation. First we do this generally, and then we specialise to the description of kink waves. We also couple this evolution equation to the slowly varying MHD formulation and solve the system in 1D. We find that the kink wave energy evolution equation contains non-linear terms, even in the absence of counterpropagating waves. The non-linear damping is expressed solely through equilibrium parameters, rather than an ad-hoc perpendicular correlation term, as in the case of the AWSOM models. A proof-of-concept numerical implementation in python shows that the kink wave driving indeed leads to radial outflow and heating. Thus, UAWSOM may have the necessary ingredients to drive the solar wind and heat the solar corona against losses. Not only does our current work constitute a pathway to fix shortcomings in heating and wind driving in the popular AWSOM model, it also provides the mathematical formalism to incorporate more wave modes for additional driving of the solar wind.