We report development of two codes: Mancha3D (single-fluid) and Mancha-2F (two-fluid). Mancha3D features modules for plasma partial ionization, realistic radiative transfer, equation of state, heat conduction, and corona radiative losses, now publicly available. Mancha-2F solves coupled equations for charged and neutral plasma components, with flexible equation sets, elastic and inelastic collisions, viscosity & conductivity.
We made a significant theoretical contribution summarizing the current knowledge of the collisionless fluid models. These models bridge the gap between traditional (MHD) fluid simulations and fully kinetic numerical simulations of the Vlasov equation. We offered a generalization of a highly-collisional Braginskii model. In our formulation, the model is expressed fully analytically through two coupled stress-tensors and two coupled heat fluxes evolution equations for multi-fluid partially ionized plasmas.
We formulated a mode conversion theory for waves in a partially ionized atmosphere. The modified Hall effect provides a new mechanism to couple fast magneto-acoustic and Alfvén waves. Along with the horizontal structuring of the solar atmosphere, this allows for the energy flux of Alfvén waves sufficient for both quiet and active region heating. Magnetic waves are efficiently dissipated through the ambipolar diffusion mechanism or frictional heating, and produce significant plasma-neutral decoupling. Gravitational stratification makes multi-fluid effects influence waves at much low frequencies.
We conducted the first-ever 3D realistic simulations of small-scale dynamo (SSD) and magneto-convection, incorporating partial ionization effects. More intricate SSD fields have a more substantial impact on chromospheric heating through the action of ambipolar and Hall mechanisms than vertically implanted fields. At characteristic times of ~10 minutes for the plasma to become ~500 K hotter at chromospheric locations where ambipolar diffusion is fully resolved in the simulations, with no signs of saturation at our best resolution of 3.5 km. Realistic 3D models of SSD in G, K, and M cool stars demonstrate inherent magnetization of their convection at ~100 G.
We carried out extremely high-resolution multi-fluid simulations of instabilities in cool coronal structures (prominences and coronal rain), fully resolving numerically the physical scales. While we observe a rich variety of multi-fluid effects in these simulations, they become especially prominent at the cool-to-hot plasma transition layers. There, ionization/recombination imbalances create overionized layers with large plasma-neutral drifts (10-20% of the flow speeds), and frictional heating of up to several thousand K, which could potentially be detected in observations.
We participated in defining science cases and instrumentation for the future 4-m EST and first light observing campaigns for DKIST telescopes. High-resolution Mancha3D simulations were used for Adaptive Optics development, and for testing inversion techniques. We undertook a challenging direct detection of plasma-neutral decoupling effects in solar prominences, revealing a slight excess in ion velocities over neutrals.
The knowledge transfer was done by means of communicating our results at multiple conferences and seminars, through collaborations, by organizing the Winter School for the PhD students and young postdocs, by with a series of dedicated workshops on Partially Ionized Plasmas in Astrophysics (PIPA), by mentoring PhD students in our group and those in collaborations.
