The Theory of Heating of the Solar Corona and Launching of the Solar Wind by Alfv\'en Waves

TL;DR

This paper develops an MHD-based model demonstrating how Alfvén waves heat the solar corona and drive the solar wind, aligning well with observations and providing insights into spectral line broadening and transition region properties.

Contribution

It introduces a method to calculate temperature and velocity profiles in the solar corona based on spectral density of Alfvén waves, supporting the Alfvén wave hypothesis for coronal heating.

Findings

Agreement with observational temperature profiles in the transition region

Prediction of angular dependence of spectral line broadening

Explanation of the narrow transition region width $\

Abstract

State-of-the-art MHD calculations reveal acceptable agreement with observational data for the height profile of the temperature $T(h)$ in the transition region of solar corona. Simultaneously, the velocity of the solar wind $U(h)$ has also been calculated. The developed method gives the possibility at given frequency dependent spectral density of Alfv\'en waves (AW) coming from chromosphere $\mathcal{W}(\omega)$ to calculate both height profiles $T(h)$ and $U(h)$. In agreement with the concepts of the self-induced opacity of plasma with respect of AW, the narrow width $\lambda$ of the transition region is determined by the fast temperature increase of the viscosity $\eta(T,B)$. After more than 70 years of development of Solar physics, the Alfv\'en hypothesis of heating of the solar corona by AW has remained without alternatives; none of other mechanisms can explain $ab$ $initio$ the value of $\lambda$. The performed MHD analysis explains the height dependence of the non-thermal broadening of the chromospheric spectral lines and predicts angular dependence of this broadening with respect of position in solar disc. One can expect significant impact of MHD analysis in the interpretation of the long expected data from Parker Solar Probe.

Full text

The Theory of Heating of the Solar Corona and Launching of the Solar Wind by Alfvén Waves

Albert Maksimov Varonov

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