标题： 浮动轨道和从磁化克尔黑洞中提取能量 显示英文标题

标题： Floating orbits and energy extraction from magnetized Kerr black holes

摘要： 我们研究了带电粒子在弱磁化克尔黑洞附近的电磁辐射反冲效应。 我们数值求解Teukolsky方程以找到视界和空间无穷远处的电磁辐射能量流。 我们也采用低频极限下的分析方法，发现与数值结果有很好的一致性。 对于广泛的参数范围，在所有轨道半径上，视界上的能量流均为负值：这些模式通过超辐射被放大。 更有趣的是，对于轨道半径为$r_0 \gtrsim 9M$的轨道，视界上的通量（绝对值）大于无穷远处的通量：浮动轨道是黑洞周围存在磁场时的普遍结果。 这些轨道上的粒子通过它们的辐射场从黑洞提取能量；净效果是粒子动能增加，因此它们向外螺旋至无穷远。 尽管在实际吸积盘中预计粘性力占主导地位，但浮动轨道仍然是黑洞时空存在能区这一特征的一个有趣现象。 显示英文摘要

摘要： We study electromagnetic radiation reaction on a charged particle around a weakly magnetized Kerr black hole. We solve numerically the Teukolsky equation to find energy fluxes in electromagnetic radiation at the horizon and at spatial infinity. We also employ analytical methods in the low-frequency limit, finding excellent agreement with the numerical results. For a wide range of parameters, energy fluxes on the horizon are negative for all orbital radii: the modes are amplified through superradiance. More interestingly, the flux on the horizon is larger (in absolute value) than the flux at infinity for orbits with orbital radius $r_0 \gtrsim 9M$ -- floating orbits are a generic outcome of having magnetic fields around black holes. Particles on these orbits extract energy from the BH through their radiation field; the net effect is an increase in the particles' kinetic energy, so that they outspiral to infinity. Although in realistic accretion disks viscous forces are expected to dominate, floating orbits remain an interesting feature of the existence of ergoregions in black hole spacetimes.