A new model for heating of Solar North Polar Coronal Hole

TL;DR

This paper develops a new model for the North Polar Coronal Hole to analyze MHD wave dissipation and propagation, considering heat conduction and viscosity, and explores their role in plasma heating and solar wind acceleration.

Contribution

It introduces a comprehensive MHD wave model for NPCH that includes anisotropic heat conduction and viscosity effects, providing insights into wave dissipation and plasma heating mechanisms.

Findings

Wave dissipation depends on viscosity and wave type.

Energy flux densities suggest waves can heat plasma and accelerate solar wind.

Parallel heat conduction causes anomalous dispersion, affecting wave propagation.

Abstract

This paper presents a new model of North Polar Coronal Hole (NPCH) to study dissipation/propagation of MHD waves. We investigate the effects of the isotropic viscosity and heat conduction on the propagation characteristics of the MHD waves in NPCH. We first model NPCH by considering the differences in radial as well as in the direction perpendicular to the line of sight (\textit{los}) in temperature, particle number density and non-thermal velocities between plumes and interplume lanes for the specific case of \ion{O}{VI} ions. This model includes parallel and perpendicular (to the magnetic field) heat conduction and viscous dissipation. Next, we derive the dispersion relations for the MHD waves in the case of absence and presence of parallel heat conduction. In the case of absence of parallel heat conduction, we find that MHD wave dissipation strongly depends on the viscosity for modified acoustic and Alfven waves. The energy flux density of acoustic waves varies between $10^{4.7}$ and $10^7 \,erg\,cm^{-2}\,s^{-1}$ while the energy flux density of Alfven waves turned out to be between $ 10^6-10^{8.6} \,erg\,cm^{-2}\,s^{-1}$. But, solutions of the magnetoacustic waves show that the parallel heat conduction introduce anomalous dispersion to the NPCH plasma wherein the group velocity of waves exceeds the speed of light in vacuum. Our results suggests all these waves may provide significant source for the observed preferential accelerating and heating of \ion{O}{VI} ions, in turn coronal plasma heating and an extra accelerating agent for fast solar wind in NPCH.