Dust dynamics in current sheets within protoplanetary disks

I. Isothermal models including ambipolar diffusion and Ohmic resistivity

¹ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
e-mail: ugo.lebreuilly@cea.fr
² École normale supérieure de Lyon, CRAL, UMR CNRS 5574, Université de Lyon, 46 allée d Italie, 69364 Lyon Cedex 07, France
³ Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
⁴ Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA

Received: 21 July 2021
Accepted: 25 May 2023

Abstract

Context. Chondrules originate from the reprocessing of dust grains. They are key building blocks of telluric planets, yet their formation, which must happen in strongly localized regions of high temperature, remains poorly understood.

Aims. We examine the dust spatial distribution near regions of strong local heating produced by current sheets, as a step toward exploring a potential path for chondrule formation. We further aim to investigate current sheet formation under various conditions in protoplanetary disks in the presence of ambipolar diffusion and Ohmic resistivity and the effect of current sheet morphology on dust dynamics in their vicinity.

Methods. We used the RAMSES code including modules for nonideal magnetohydrodynamics and the solution of the dynamics of multiple sizes of dust grains to compute unstratified shearing box simulations of current sheet formation. Through seven models, we investigated the effect of the ambipolar diffusion and Ohmic resistivity strength, the initial density, and magnetic field, as well as the resolution and box size.

Results. We find that current sheets form in all our models, with typical widths of 10⁻³–10⁻² AU, and that strong dust fraction variations occur for millimeter-sized grains. These variations are typically of an order of magnitude and up to two orders of magnitude for the most favorable cases. We also show that the box size and resolution has a strong impact on the current sheet distribution and intensity.

Conclusions. The formation of current sheets that can intensely heat their surroundings near strong dynamical dust fraction variations could have important implications for chondrule formation, as it appears likely to happen in regions with a large dust fraction.