Twofluid simulations of waves in the solar chromosphere. I. Numerical code verification
Abstract
Solar chromosphere consists of a partially ionized plasma, which makes modeling the solar chromosphere a particularly challenging numerical task. Here we numerically model chromospheric waves using a twofluid approach with a newly developed numerical code. The code solves twofluid equations of conservation of mass, momentum, and energy, together with the induction equation for the case of the purely hydrogen plasma with collisional coupling between the charged and neutral fluid components. The implementation of a semiimplicit algorithm allows us to overcome the numerical stability constraints due to the stiff collisional terms. We test the code against analytical solutions of acoustic and Alfvén wave propagation in uniform medium in several regimes of collisional coupling. The results of our simulations are consistent with the analytical estimates, and with other results described in the literature. In the limit of a large collisional frequency, the waves propagate with a common speed of a single fluid. In the other limit of a vanishingly small collisional frequency, the Alfvén waves propagate with an Alfvén speed of the charged fluid only, while the perturbation in neutral fluid is very small. The acoustic waves in these limits propagate with the sound speed corresponding to either the charges or the neutrals, while the perturbation in the other fluid component is negligible. Otherwise, when the collision frequency is similar to the real part of the wave frequency, the interaction between charges and neutrals through momentumtransfer collisions cause alterations of the waves frequencies and damping of the wave amplitudes.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 July 2019
 DOI:
 10.1051/00046361/201834154
 arXiv:
 arXiv:1905.03559
 Bibcode:
 2019A&A...627A..25P
 Keywords:

 Sun: chromosphere;
 Sun: oscillations;
 Sun: magnetic fields;
 methods: numerical;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Computational Physics;
 Physics  Plasma Physics;
 Physics  Space Physics
 EPrint:
 A&