Magnetohydrodynamics of charged interstellar dust. Multifluid models and study of the linear modes
Year: 2026
Type: article
Abstract: Interstellar grains play key roles in star and planet formation, including in the coupling of gas to the magnetic field during protostellar collapse. The significance of these roles depends on the local grain size distribution, which requires a multifluid treatment of charged dust. We aim to understand the fundamental physics of the dynamics of a dust distribution in interaction with the gas and the magnetic field. In particular, our purpose is to characterize the (de)coupling conditions of these different components. We provide a multifluid model of charged dust that accounts for the inertia of the grains. We used a chemical network to simulate the charge equilibrium in collapsing protostellar cores. We computed the Alfvén modes and the magnetosonic modes to understand the coupling regimes between the gas, the dust fluids, and the magnetic field. We also analyzed and compared to the predictions of existing models, namely of the neutral dust multifluid and the standard non-ideal magnetohydrodynamics. The charged multifluid model agrees with non-ideal magnetohydrodynamics on the larger scales of a collapsing dense core and the forming disk, while we successfully extend to new regimes where the inertia of dust grains matters. We find that high charge-to-mass dust grains carry the propagation of magnetohydrodynamical waves in protostellar envelopes. We provide analytical expressions of the speed of these waves depending on the dust distribution. The magnetocompressive perturbations lead to local dust-to-gas ratio variations at astronomical unit scales. A theoretical understanding of the dynamics of a charged dust distribution is provided in the linear regime. The closed set of magnetohydrodynamics equations can be implemented in numerical codes to explore nonlinear effects during the protostellar collapse, such as turbulence, angular momentum transport, and magnetic dust clumping.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funder: European Research Council
Award: G6018591478
OpenAlex ID: W7204868172