OUTBURSTS FROM A BLACK-HOLE VIA ALFVEN-WAVE TO ELECTROMAGNETIC-WAVE MODE CONVERSION

A new mechanism for outbursts from a black hole is proposed. A recent work on general relativistic plasma equilibria around a black hole has shown the possibility of equilibrium presence of matter and magnetic fields in the neighborhood of the event horizon, even where the corpus cular equilibrium is not allowed (r < 3R(s), where R-s is the Schwarzs child radius). A large-amplitude Alfven pulse in the black hole electr on-positron atmosphere that propagates away from the hole into lower m agnetic field regions can experience resonance and mode-convert itself into a large-amplitude electromagnetic (EM) pulse. It is shown theore tically and computationally that through this process a large amount o f mass can be picked up by the solitary EM pulse capable of traveling in a vacuum, with which particles are accelerated to relativistic ener gies. Photon spectra are obtained not inconsistent with observation, w hich follow a multiple power law with log-log slopes of approximately -1, before a ''knee'' in the spectrum at energies slightly greater tha n 1 MeV. It is suggested that this may be a possible mechanism for the outbursts of the black hole binary GRO J1655-40.