Global MHD instabilities: from Low Frequency to High Frequency QPOs, and to Sgr A*

Abstract

I review recent work that goes beyond our model for the Low-Frequency Quasi-Periodic Oscillation of microquasars, based on the Accretion-Ejection Instability. I show that similar instabilities, which can be viewed as strongly unstable versions of the diskoseismologic modes, provide explanations for both the High-Frequency QPO and for the quasi-periodicity observed durng the flares of Sgr A*, the supermassive black hole at the Galactic Center.

11 pages, 8 figures, in the proceedings of the VI Microquasar Workshop "Microquasars and beyond", Como, 2006 Sep 18-22 (Italy), ed: T. Belloni (2006), PoS(MQW6)031