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SUMMARY:Trapped Inertial Waves in Magnetohydrodynamic\, Relativistic Accre
 tion Disks - Janosz Dewberry
DTSTART:20161122T130000Z
DTEND:20161122T140000Z
UID:TALK68496@talks.cam.ac.uk
CONTACT:Jean Teyssandier
DESCRIPTION:Semi-periodic variability has been observed for years in emiss
 ion from black hole candidates\, primarily by the Rossi X-Ray Timing Explo
 rer\, with `quasi-periodic oscillations' (QPOs) appearing as coherent peak
 s in the power density spectrum as frequencies of ~0.1-450 Hz. The QPOs wi
 th higher frequencies of 40-450Hz (HFQPOs) attract particular interest bec
 ause their frequencies roughly match those expected for matter orbiting ne
 ar the innermost stable circular orbit (ISCO)\, and remain stable to varia
 tions in luminosity. These characteristics suggest that HFQPOs might offer
  a probe into the intrinsic properties of the central black hole\, specifi
 cally the spin angular momentum. One explanation for HFQPOs is the trappin
 g and amplification of global `diskoseismic' oscillations in the inner reg
 ions of the surrounding accretion disk\, in particular the so-called `grav
 ito-inertial' waves\, or r-modes. In a purely hydrodynamic context\, r-mod
 es can be confined by relativistic effects within a resonant cavity distin
 ct from the ISCO\, and can grow in amplitude through couplings with warps 
 and eccentricities. However\, recent work has called into question the sur
 vival of trapped inertial waves in the presence of magnetohydrodynamic tur
 bulence\, and the very existence of the self-trapping region in an accreti
 on disk threaded by large-scale magnetic fields. I summarise semi-analytic
 al and numerical work aimed at addressing these questions of existence and
  persistence more fully. 
LOCATION:MR11\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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