Wave propagation and energy transport in the magnetic network of the Sun

TL;DR

This study uses 2-D MHD simulations to analyze wave propagation and energy transport in solar magnetic flux concentrations, revealing how magnetic field strength and boundary-layer thickness influence energy fluxes and mode conversion.

Contribution

It provides a quantitative evaluation of energy transport modes and the impact of boundary-layer thickness on wave propagation in solar magnetic elements.

Findings

Strong magnetic fields enhance acoustic flux to the chromosphere.

Insufficient energy in acoustic flux to offset chromospheric radiative losses.

Wider boundary layers reduce acoustic emission from flux interfaces.

Abstract

We investigate wave propagation and energy transport in magnetic elements, which are representatives of small scale magnetic flux concentrations in the magnetic network on the Sun. This is a continuation of earlier work by Hasan et al. (2005). The new features in the present investigation include a quantitative evaluation of the energy transport in the various modes and for different field strengths, as well as the effect of the boundary-layer thickness on wave propagation. We carry out 2-D MHD numerical simulations of magnetic flux concentrations for strong and moderate magnetic fields. Waves are excited in the tube and ambient medium by a transverse impulsive motion of the lower boundary. The nature of the modes excited depends on the value of beta. Mode conversion occurs in the moderate field case when the fast mode crosses the beta=1 contour. In the strong field case the fast mode undergoes conversion from predominantly magnetic to predominantly acoustic when waves are leaking from the interior of the flux concentration to the ambient medium. We also estimate the energy fluxes in the acoustic and magnetic modes. The main conclusions of our work are twofold: firstly, for transverse, impulsive excitation, flux tubes/sheets with strong fields are more efficient than those with weak fields in providing acoustic flux to the chromosphere. However, there is insufficient energy in the acoustic flux to balance the chromospheric radiative losses in the network, even for the strong field case. Secondly, the acoustic emission from the interface between the flux concentration and the ambient medium decreases with the width of the boundary layer.