Monochromatic Two-Fluid Alfvén Waves in the Partially Ionised Solar Chromosphere

Abstract

We present new results towards the explanation of the chromospheric-heating problem and the solar-wind origin, using a two-fluid model that takes into account the collisional interaction between ions (protons) and neutrals (hydrogen atoms). Our aim is to further reveal the mechanism behind chromospheric heating and plasma outflows. We simulate and analyse the propagation and evolution of Alfvén waves in the partially ionised solar chromosphere, consisting of ions + electrons and neutral fluids. The simplified model chromosphere is permeated by a vertical, uniform magnetic field. We perform numerical simulations in the framework of a quasi-1.5-dimensional (1.5D), two-fluid model in which Alfvén waves are excited by a harmonic driver in the transverse component of the ion and neutral velocities, operating in the chromosphere. In the case of a small-amplitude driver, Alfvén waves are weakly damped, and for the chosen wave periods of a few seconds, Alfvén waves manage to propagate through the chromosphere and enter the solar corona. Non-linear Alfvén waves excited by a large-amplitude driver cause significant chromospheric heating and plasma outflows. We thus conclude that two-fluid Alfvén waves with larger amplitudes can contribute to chromospheric heating and plasma outflows, which may result higher up in the solar-wind origin.

Magnetohydrodynamic waves in the partially ionized solar plasma

“…Since the findings from [42] were derived from linear wave analysis, validation via nonlinear simulations is needed, such as those conducted by Boocock & Tsiklauri [130] albeit without the inclusion of partial ionization effects. Indeed, some studies have extended the exploration of Alfvén wave heating in the chromosphere, employing two-fluid numerical simulations (see, for instance, [110,[131][132][133]). These investigations reaffirm that high-frequency Alfvén waves could contribute significantly to heating the chromospheric plasma, as earlier research had indicated.…”

Estimated electric conductivities of thermal plasma for air-fuel combustion and oxy-fuel combustion with potassium or cesium seeding

“…Thus, the number density of electrons is not recommended to exceed 0.001 (0.1 %) of the number density of neutrals in the plasma [ 91 ]. With such weak ionization, the use of ideal gas law is valid, and is not violated by the small fraction of electrons added to the neutral particles and the small fraction of neutrals that turn into ions [ 92 , 93 ].…”