Production of the large scale superluminal ejections of the microquasar GRS 1915+105 by violent magnetic reconnection

We propose here that the large-scale superluminal ejections observed in the galactic microquasar GRS 1915+105 during radio flare events are produced by violent magnetic reconnection episodes in the corona just above the inner edge of the magnetized accretion disk that surrounds the central similar to 10 M-circle dot black hole. The process occurs when a large-scale magnetic field is established by a turbulent dynamo in the inner disk region with a ratio between the gas+radiation and the magnetic pressures beta similar or equal to 1, implying a magnetic field intensity of similar to 7 x 10(8) G. During this process, substantial angular momentum is removed from the disk by the wind generated by the vertical magnetic flux therefore increasing the disk mass accretion to a value near (but below) the critical one (M similar to 10(19) g s(-1)). Part of the magnetic energy released by reconnection heats the coronal gas (T-c less than or similar to 5 x 10(8) K) that produces a steep X-ray spectrum with luminosity L-X similar or equal to 10(39) erg s(-1), consistent with observations. The remaining magnetic energy released goes to accelerate the particles to relativistic velocities (v similar to v(A) similar to c, where vA is the Alfven speed) in the reconnection site through first-order Fermi processes. In this context, two possible mechanisms have been examined that produce power-law electron distributions N(E) proportional to E-alpha E, with alpha(E) = 5/2, 2, and corresponding synchrotron radio power-law spectra with spectral indices which are compatible with that observed during the flares (S-v proportional to v(-0.75,-0.5)).