Heating of a Quiet Region of the Solar Chromosphere by Ion and Neutral Acoustic Waves

Abstract

Using high-resolution numerical simulations we investigate the plasma heating driven by periodic two-fluid acoustic waves that originate at the bottom of the photosphere and propagate into the gravitationally stratified and partially ionized solar atmosphere. We consider ions+electrons and neutrals as separate fluids that interact between themselves via collision forces. The latter play an important role in the chromosphere, leading to significant damping of short-period waves. Long-period waves do not essentially alter the photospheric temperatures, but they exhibit the capability of depositing a part of their energy in the chromosphere.This results in up about a five times increase of ion temperature that takes place there on a time-scale of a few minutes. The most effective heating corresponds to waveperiods within the range of about 30-200 s with a peak value located at 80 s. However, we conclude that for the amplitude of the driver chosen to be equal to 0.1 km s −1 , this heating is too low to balance the radiative losses in the chromosphere.

Numerical simulations of the lower solar atmosphere heating by two-fluid nonlinear Alfvén waves

“…We clearly see that V i z (corresponding to Alfvén waves) is partially transferred into magnetoacoustic waves (denoted by both the dotted line for V i x and by the dashed line representing V i y ). Moreover, we conclude that the plasma escaping into the corona above the transition region carries a significant amount of mass density and energy, possibly contributing to overall plasma outflows and solar wind (Wójcik et al 2019). We note that the obtained values of mass and energy fluxes lay within the range of theoretical findings for energy losses in the upper chromosphere estimated by Withbroe & Noyes (1977).…”

“…Indeed, Fig. 6 (top-right) reveals a growth of the plasma temperature close to the bottom boundary up to δT i ≈ 200 K over a timescale of 250 s. We note that acoustic (Kuźma et al 2019) and fast magneto-acoustic waves (Popescu Braileanu et al 2019) behave differently from Alfvén waves, as they contribute to plasma heating in the chromosphere, whereas Alfvén waves directly thermalize their energy in the low photosphere. A first attempt to understand how the heating and cooling processes modify the properties of MHD waves in a fully ionized medium in the case of solar prominence was made by Ballester et al (2016).…”

“…This time results from the time needed for Alfvén waves to propagate, to drive magneto-acoustic waves, and for the latter to travel through the chromosphere and reflect from the transition region. We note that after this time the solar granulation in the photosphere is also developed, which can excite magneto-acoustic waves (Wójcik et al 2019).…”

“…(1)-( 7). This code is based on high-order Godunov-type methods (Wójcik et al 2018(Wójcik et al , 2019 and uses the divergence-cleaning method of Dedner et al (2002) to control the ∇ • B = 0 constraint.…”

“…We see that V i x dominates in the upper photosphere (top-left), where the magnetic field lines are strongly curved and almost become horizontal, while V i y prevails in chromospheric regions that are permeated by vertical magnetic field (top-right). The energy of these waves is deposited in the form of thermal energy heating the plasma, and the energy is released during ionneutral collisions; see also Kuźma et al (2019) who showed that two-fluid acoustic waves with their wave periods of 30 − 120 s effectively heat chromospheric plasma. Indeed, Fig.…”