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Simulating the acceleration of dust grains in interstellar turbulence

Presentation #328.04 in the session Dust.

Published onJun 29, 2022
Simulating the acceleration of dust grains in interstellar turbulence

Interstellar dust grains play a significant role in shaping the spectrum of interstellar and extragalactic radiation, reprocessing perhaps 30% of the energy emitted from stars into the infrared. Most of this reprocessing is produced by small grains < 0.01 μm in size. However, it is thought that grains are initially produced at relatively large sizes in supernova ejecta and stellar winds. As such, small grains are likely produced via the shattering of large grains that have been stochastically accelerated to high velocities. To understand this stochastic acceleration, we have implemented novel magnetohydrodynamic(MHD)-particle-in-cell(PIC) methods into the astrophysical fluid code RAMSES. We treat dust grains as a set of massive particles that experience aerodynamic drag and electromagnetic forces. Under the influence of these forces, we follow the motion of dust grains embedded in ideal MHD turbulence. We find that dust grains approximately 1 μm in size can be effectively accelerated to well beyond their shattering velocities in typical cold neutral medium conditions. This is true for both electrically charged and neutral grains. While the peak of the gas-grain relative drift velocity distribution is higher for neutral grains, the drift velocity distribution of charged grains exhibits an extended exponential tail out to much greater velocities.

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