An Electromagnetic Model for Jet Power from an Advection Dominated Accretion Flow around a Rotating Black Hole

We discuss jet production from an advection dominated accretion flow (ADAF) around a rotating black hole (BH) in an electromagnetic regime. An analytical expression for the jet power is derived by using an equivalent circuit in the BH magnetosphere. It turns out that a large fraction of jet powers is contributed from the inner region of the ADAF, and the jet power depends sensitively on the degree to which the flow is advection-dominated. In addition, we use our model to fit the strong jet powers of several BL Lac objects, which cannot be explained by virtue of the BZ process.     

Magnetic Extraction of Energy from Accretion Disc Around a Rotating Black Hole

An analytical expression for the jet power extracted from the disc (JPEFD) is derived based on an equivalent circuit in black hole magnetosphere with a mapping relation between the radial coordinate of the disc and that of unknown astrophysical load. It turns out that this JPEFD is comparable with two other JPEFDs derived in the Poynting flux and hydrodynamic regimes, respectively. In addition, the relative importance of this JPEFD relative to the Blandford-Znajek power is discussed. It is shown that the BZ power is generally dominated by the JPEFD except in some extreme cases. Furthermore, we show that the JPEFD derived in our model can be well fitted with the jet power of 3C 273.     

A Unified Model of Magnetic Extraction of Spin Energy from a Black Hole

A unified model of magnetic extraction of spin energy from a black hole in discussed based on the theory of black hole magnetosphere.The magnetic extracting power is expressed by a unified formula,which is applicable to bloth the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process.The strength and characteristics of the BZ power and the MC power are compared in detail.In addition,the impedance matching condition for the BZ power is extended to the more general case.     

Electromagnetic Quantities in Black Hole Magnetosphere

Some electromagnetic quantities in the black hole (BH) magnetosphere are discussed by considering the coexistence of the Blandford-Znajek process and the magnetic coupling process. These quantities are (i) flux of electromagnetic energy and angular momentum transferred between the BH and the disc, (ii) poloidal currents flowing on the     

Effects of Magnetic Coupling on Profile of Emission Lines and Images of an Accretion Disc Around a Black Hole

The profiles of emission lines and images of an accretion disc around a black hole (13tt) are simulated by considering the effects of the magnetic coupling (MC) of a central BH with the disc. The MC effects are discussed for both slow- and fast-spinning BHs, and the following results are obtained. Firstly, the width of the emission lines and the brightness of the disc are reduced and augmented for slow- and fast-spinning BHs, respectively. Secondly,the image of the disc becomes dimmer and brighter near the inner edge of the disc for slow- and fast-spinning BHs, respectively. It turns out that all these results arise from the MC effects on the position of the dominant emission region of the accretion disc.     

A New Approach to Black hole Spin in X-Ray Binaries

A new approach of detecting the black hole spin in x-ray binaries is proposed based on the model of the coexistence of the Blandford-Znajek （BZ） and magnetic coupling （MC） processes, in which the BZ process is used to power the jet emissions from x-ray binaries, and high frequency quasi-periodic oscillations （QPOs） are explained by a rotating hotspot in the inner region of the accretion disc surrounding a fast-spinning black hole. It is shown that the black hole spins of several x-ray binaries （XTE J1550-564, GRO d1665-40 and GRS 1915＋105） can be constrained in a rather narrow range, provided that QPOs and jets coexist in these sources.     

Screw Instability in Black Hole Magnetosphere and kHz QPOs in X-Ray Binaries

Screw instability of the magnetic field connecting a rotating black hole (BH) with its surrounding disc is discussed in coexistence with the Blandford-Znajek (BZ) process and the magnetic coupling (MC) process. A scenario for kilohertz quasi-periodic oscillations (kHz QPOs) in x-ray binaries is proposed by introducing inductance components in the equivalent circuit for BH magnetosphere. It turns out that the period related to the screw instability is consistent with the observations of kHz QPO x-ray binaries.     

黑洞自转角速度的演化特征

在同时考虑吸积和Blandford-Znajek过程的条件下,详细讨论了吸积盘（包括薄盘和厚盘）中心黑洞的自转角速度Ω_h的演化特征.结果表明,当黑洞的无量纲角动量a_*演化到某一临界时,Ω_h对时间的变化率由正变负,从而推断在顺行吸积过程事Ω_h先增后减,演化非单调,因而存在一个极大值.并指出黑洞的无量纲角动理a_*比黑洞的角动量J和自转角速度Ω_h更适合描写吸积盘中心黑洞自转状态的演 关键词：     

Energy Extraction from a Black Hole and Its Influence on X-Ray Spectra

The famous jet production mechanism, i.e. the Blandford and Znajek （BZ） process, has realized the idea proposed by Penrose that the rotational en- ergy of a black hole （BH） could be extracted from the ergosphere. In the BZ process, large-scale magnetic fields connecting the BH horizon and the remote as- trophysical load can extract the energy and angular momentum of the rotating BH in the form of electro- magnetic energy. The BZ mechanism was successful in explaining astrophysical jets and was widely used in high energy astrophysics. As a variation of the BZ process, the magnetic connection （MC） between the BH horizon and the accretion disk, namely, the MC process, was later discussed by researchers. Li discovered that the extractable energy of an extreme Kerr BH in the MC process can reach ～0.15Mc2, which is higher than that in the BZ process, where M is the BH mass and c is the light speed. In recent years, some astrophysical phenomena observed in BH systems, such as broad iron emission lines and high frequency quasi-periodic oscillations （QPOs）, re- veal the importance of the MC process. How- ever, we are still interested in how the extracted en- ergy is dissipated in the inner accretion disk and how it affects the accretion flow and the x-ray spectrum remains unclear.     

Effects of Screw Instability on Extracting Energy from a Rotating Black Hole

Magnetic extraction of energy from a rotating black hole (BH) is discussed in the coexistence of the BlandfordZnajek (BZ) process and the magnetic coupling (MC) process by considering the effects of the screw instability of the magnetic field. It is shown that the screw instability affects the configuration of the magnetosphere and the evolution characteristics of the BH, augmenting the energy extracted in the BZ and MC processes. In addition, the observed energy and duration of several gamma-ray bursts can be fitted well by virtue of our model.