Two-fluid simulations of waves in the solar chromosphere I: numerical code verification. (arXiv:1905.03559v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Braileanu_B/0/1/0/all/0/1">B. Popescu Braileanu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lukin_V/0/1/0/all/0/1">V. S. Lukin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khomenko_E/0/1/0/all/0/1">E. Khomenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vicente_A/0/1/0/all/0/1">A. de Vicente</a>
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 two-fluid approach with a
newly developed numerical code. The code solves two-fluid 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
semi-implicit 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 Alfv’en 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 Alfv’en waves
propagate with an Alfv’en 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 very small.
Otherwise, when the collision frequency is similar to the real part of the wave
frequency, the interaction between charges and neutrals through momentum
transfer collisions cause alterations of the waves frequencies and damping of
the wave amplitudes.
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 two-fluid approach with a
newly developed numerical code. The code solves two-fluid 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
semi-implicit 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 Alfv’en 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 Alfv’en waves
propagate with an Alfv’en 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 very small.
Otherwise, when the collision frequency is similar to the real part of the wave
frequency, the interaction between charges and neutrals through momentum
transfer collisions cause alterations of the waves frequencies and damping of
the wave amplitudes.
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