,Magnetic extraction of energy from black hole accretion disc and its application to astrophysics

• 作 者: Ye Yong-Chn Wang Ding-Xiong Gong Xiao-Long
• 机 构: Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
• 出 处: 中国物理（英文版）
• 发表日期: 2005年2期
• 关键词: black holes black hole physics accretion discs emissivity index

A new configuration of magnetic field (NCMF) in black hole (BH) magnetosphere is proposed by considering the effects of the screw instability. Three mechanisms of extracting energy magnetically are involved in the NCMF: (1)the Blandford-Znajek (BZ) process; (2) the magnetic coupling (MC) process; (3) a new scenario (henceforth the DL process) for extracting rotational energy from the disc, which is related to the open field lines connecting the disc with the astrophysical load. The expressions for the powers and torques of the above energy mechanisms are derived by using two kinds of the equivalent circuits. It tus out that the power and efficiency of extracting energy magnetically from the BH accretion disc are all augmented in the NCMF. It is shown that a very steep emissivity can be produced in a NCMF,which is consistent with the recent XMM-Newton observation of the nearby bright Seyfert 1 galaxy MCG-6-30-15.