Photon bubbles in accretion discs

Research output: Contribution to journalArticlepeer-review


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 languageEnglish (US)
Pages (from-to)929-935
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Jul 1 1998
Externally publishedYes


  • Accretion, accretion discs
  • Instabilities
  • MHD

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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