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Neutral-charged-particle Collisions as the Mechanism for Accretion Disk Angular Momentum Transport

Zhang, Yang and Bellan, Paul M. (2022) Neutral-charged-particle Collisions as the Mechanism for Accretion Disk Angular Momentum Transport. Astrophysical Journal, 930 (2). Art. No. 167. ISSN 0004-637X. doi:10.3847/1538-4357/ac62d5.

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The matter in an accretion disk must lose angular momentum when moving radially inwards but how this works has long been a mystery. By calculating the trajectories of individual colliding neutrals, ions, and electrons in a weakly ionized 2D plasma containing gravitational and magnetic fields, we numerically simulate accretion disk dynamics at the particle level. As predicted by Lagrangian mechanics, the fundamental conserved global quantity is the total canonical angular momentum, not the ordinary angular momentum. When the Kepler angular velocity and the magnetic field have opposite polarity, collisions between neutrals and charged particles cause: (i) ions to move radially inwards, (ii) electrons to move radially outwards, (iii) neutrals to lose ordinary angular momentum, and (iv) charged particles to gain canonical angular momentum. Neutrals thus spiral inward due to their decrease of ordinary angular momentum while the accumulation of ions at small radius and accumulation of electrons at large radius produces a radially outward electric field. In 3D, this radial electric field would drive an out-of-plane poloidal current that produces the magnetic forces that drive bidirectional astrophysical jets. Because this neutral angular momentum loss depends only on neutrals colliding with charged particles, it should be ubiquitous. Quantitative scaling of the model using plausible disk density, temperature, and magnetic field strength gives an accretion rate of 3 × 10−8 solar mass per year, which is in good agreement with observed accretion rates.

Item Type:Article
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URLURL TypeDescription
Zhang, Yang0000-0002-4168-9225
Bellan, Paul M.0000-0002-0886-8782
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 24; revised 2022 March 3; accepted 2022 March 21; published 2022 May 17. This material is based upon work supported by NSF award Nos. 2105492 and 1914599.
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Subject Keywords:Accretion; Stellar accretion; Jets; Plasma jets; Protoplanetary disks; Circumstellar disks; Plasma astrophysics
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Accretion (14); Stellar accretion (1578); Jets (870); Plasma jets (1263); Protoplanetary disks (1300); Circumstellar disks (235); Plasma astrophysics (1261)
Record Number:CaltechAUTHORS:20220525-90461000
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Official Citation:Yang Zhang and Paul M. Bellan 2022 ApJ 930 167
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114914
Deposited By: George Porter
Deposited On:31 May 2022 15:32
Last Modified:31 May 2022 15:32

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