Volume 441, Number 3, October III 2005
|Page(s)||845 - 853|
|Published online||23 September 2005|
Production of the large scale superluminal ejections of the microquasar GRS 1915+105 by violent magnetic reconnection
Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil e-mail: firstname.lastname@example.org
2 Department of Astronomy, University of Wisconsin, Madison, USA e-mail: email@example.com
Accepted: 13 June 2005
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 ~ 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 , implying a magnetic field intensity of ~ 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 ( g s-1). Part of the magnetic energy released by reconnection heats the coronal gas ( K) that produces a steep X-ray spectrum with luminosity erg s- 1, consistent with observations. The remaining magnetic energy released goes to accelerate the particles to relativistic velocities (, where vA is the Alfvén 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 , with , and corresponding synchrotron radio power-law spectra with spectral indices which are compatible with that observed during the flares ().
Key words: acceleration of particles / accretion, accretion disks / black hole physics / magnetic fields
© ESO, 2005
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