Session B16 - Neutrino and Gamma Ray Astrophysics.
MIXED session, Saturday morning, April 29
202C, Convention Center
Magnetized accretion disks are shown to be subject to collective processes, that can induce the needed outward transport of angular momentum, whose growth rates, as in the case of laboratory plasmas depend on the finiteness of the plasma temperature(B. Coppi and P.S. Coppi, \itPhys. Lett. A)239\rm, 261 (1998) and on the gradient of the rotation frequency(E. Velikhov, \itSoviet Phys.) JETP36\rm, 1938 (1959); S.A. Balbus and J.F. Hawley, \itAp. J. \bf376\rm, 214 (1991) combined. Therefore accretion is envisioned to occur as a sequence of two stages: i) a preheating phase of accumulated plasmas at the outer edge of the disk and ii) a rapid infalling phase following the excitation of the relevant modes. The proposed scenario is similar to that of the so called ``monster sawtooth oscillations'' occuring in magnetically confined laboratory plasmas where the central temperature is observed to rise, as a result of the injection of a high energy particle population and then to crash periodically. The crash leads to a spatial redistribution of the thermal energy and is caused by the excitation of internal modes driven by the plasma pressure gradient when this is raised above a characteristic threshold by the energy transferred from the injected particles to the thermal plasma.
Sponsored in part by the U.S. Department of Energy