论文标题
磁重新连接作为从旋转黑洞中提取能量的机制
Magnetic Reconnection as a Mechanism for Energy Extraction from Rotating Black Holes
论文作者
论文摘要
旋转黑洞存储旋转能，可以提取。当黑洞浸入外部提供的磁场中时，梯形内的磁场线的重新连接会产生负能量（相对于无穷大）颗粒，这些颗粒落入黑洞事件地平线中，而其他颗粒逃脱了从黑洞中窃取能量。我们分析表明，当黑洞旋转高（无量纲旋转$ a \ sim1 $）并且等离子体被强烈磁化时，可以通过磁重新连接进行能量提取（等离子体磁化$σ_0> 1/3 $）。允许能量提取的参数空间区域取决于等离子体磁化和重新连接磁场线的方向。对于$σ_0\ gg 1 $，发现被最大旋转黑洞吞咽的减速等离子体的无穷大的渐近负能量被发现为$ε^\ infty_- \ simeq - \ sqrt {σ_0/3} $。逃脱到无穷大的加速等离子体将黑洞能量渐近为无穷大，每焓$ε^\ infty_+ \ simeq \ simeq \ sqrt {3σ_0} $。我们表明，通过逃逸血浆从黑洞中提取的最大功率为$ p _ {\ rm extres}^{\ rm max} \ sim 0.1 m^2 \ sqrt {σ_0} \，w_0 $对于碰撞政权。当$ a \ sim 1 $时，能量提取会导致黑洞的大量染色。发现通过磁重连接在Ergosphere中的等离子能量过程的最大效率为$η_{\ rm max} \ simeq 3/2 $。由于在此处提出的方案中应间歇性地发生Ergosphere中的快速磁重新连接，因此，黑洞中几个重力半径内的相关发射有望表现出爆发性质。
Spinning black holes store rotational energy that can be extracted. When a black hole is immersed in an externally supplied magnetic field, reconnection of magnetic field lines within the ergosphere can generate negative energy (relative to infinity) particles that fall into the black hole event horizon while other particles escape stealing energy from the black hole. We show analytically that energy extraction via magnetic reconnection is possible when the black hole spin is high (dimensionless spin $a\sim1$) and the plasma is strongly magnetized (plasma magnetization $σ_0>1/3$). The parameter space region where energy extraction is allowed depends on the plasma magnetization and the orientation of the reconnecting magnetic field lines. For $σ_0 \gg 1$, the asymptotic negative energy at infinity per enthalpy of the decelerated plasma that is swallowed by a maximally rotating black hole is found to be $ε^\infty_- \simeq - \sqrt{σ_0/3}$. The accelerated plasma that escapes to infinity and takes away black hole energy asymptotes the energy at infinity per enthalpy $ε^\infty_+ \simeq \sqrt{3σ_0}$. We show that the maximum power extracted from the black hole by the escaping plasma is $P_{\rm extr}^{\rm max} \sim 0.1 M^2\sqrt{σ_0}\,w_0$ (here, $M$ is the black hole mass and $w_0$ is the plasma enthalpy density) for the collisionless plasma regime and one order of magnitude lower for the collisional regime. Energy extraction causes a significant spindown of the black hole when $a \sim 1$. The maximum efficiency of the plasma energization process via magnetic reconnection in the ergosphere is found to be $η_{\rm max} \simeq 3/2$. Since fast magnetic reconnection in the ergosphere should occur intermittently in the scenario proposed here, the associated emission within a few gravitational radii from the black hole is expected to display a bursty nature.
