Abstract
We show that radiation-dominated accretion discs are likely to suffer from a 'photon bubble' instability similar to that described by Arons in the context of accretion on to neutron star polar caps. The instability requires a magnetic field for its existence. In an asymptotic regime appropriate to accretion discs, we find that the overstable modes obey the remarkably simple dispersion relation ω2 = - igkF(B, k). Here g is the vertical gravitational acceleration, B is the magnetic field, and F is a geometric factor of order unity that depends on the relative orientation of the magnetic field and the wavevector. In the non-linear outcome it seems likely that the instability will enhance vertical energy transport and thereby change the structure of the innermost parts of relativistic accretion discs.
Original language | English (US) |
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Pages (from-to) | 929-935 |
Number of pages | 7 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 297 |
Issue number | 3 |
DOIs | |
State | Published - Jul 1 1998 |
Externally published | Yes |
Keywords
- Accretion, accretion discs
- Instabilities
- MHD
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science