MRI-active inner regions of protoplanetary discs. I. A detailed model of disc structure
File(s)
Accepted version
OA Location
Author(s)
Jankovic, Marija R
Owen, James E
Mohanty, Subhanjoy
Tan, Jonathan C
Type
Journal Article
Abstract
Short-period super-Earth-sized planets are common. Explaining how they form near their present orbits requires understanding the structure of the inner regions of protoplanetary discs. Previous studies have argued that the hot inner protoplanetary disc is unstable to the magnetorotational instability (MRI) due to thermal ionization of potassium, and that a local gas pressure maximum forms at the outer edge of this MRI-active zone. Here we present a steady-state model for inner discs accreting viscously, primarily due to the MRI. The structure and MRI-viscosity of the inner disc are fully coupled in our model; moreover, we account for many processes omitted in previous such models, including disc heating by both accretion and stellar irradiation, vertical energy transport, realistic dust opacities, dust effects on disc ionization, and non-thermal sources of ionization. For a disc around a solar-mass star with a standard gas accretion rate (M˙∼10−8 M⊙ yr−1) and small dust grains, we find that the inner disc is optically thick, and the accretion heat is primarily released near the mid-plane. As a result, both the disc mid-plane temperature and the location of the pressure maximum are only marginally affected by stellar irradiation, and the inner disc is also convectively unstable. As previously suggested, the inner disc is primarily ionized through thermionic and potassium ion emission from dust grains, which, at high temperatures, counteract adsorption of free charges on to grains. Our results show that the location of the pressure maximum is determined by the threshold temperature above which thermionic and ion emission become efficient.
Date Issued
2021-04-16
Date Acceptance
2021-03-29
Citation
Monthly Notices of the Royal Astronomical Society, 2021, 504 (1), pp.280-299
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Start Page
280
End Page
299
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
504
Issue
1
Copyright Statement
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). This is a pre-copy-editing, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version Marija R Jankovic, James E Owen, Subhanjoy Mohanty, Jonathan C Tan, MRI-active inner regions of protoplanetary discs. I. A detailed model of disc structure, Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 1, June 2021, Pages 280–299 is available online at: https://doi.org/10.1093/mnras/stab920
This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). This is a pre-copy-editing, author-produced version of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version Marija R Jankovic, James E Owen, Subhanjoy Mohanty, Jonathan C Tan, MRI-active inner regions of protoplanetary discs. I. A detailed model of disc structure, Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 1, June 2021, Pages 280–299 is available online at: https://doi.org/10.1093/mnras/stab920
Sponsor
The Royal Society
Commission of the European Communities
Grant Number
UF150412
853022
Subjects
0201 Astronomical and Space Sciences
Astronomy & Astrophysics
Publication Status
Published
Date Publish Online
2021-04-01