arXiv subjects

Kevin Thoelecke

Publications and source records attributed to Kevin Thoelecke.

3 recordsLinked to original sources

arXiv2019

The Structure of Magnetically Dominated Energy Extracting Black Hole Magnetospheres: Dependencies on Field Line Angular Velocity

If a magnetically dominated magnetosphere is to extract a black hole's rotational energy and transmit it to distant regions, then the inner light surface of that magnetosphere must lie within the ergoregion. That inner light surface condition limits the angular velocity of magnetic field lines. We take the distribution of magnetic field line angular velocity on the horizon to be a useful proxy for inner light surface location and study how different distributions affect the structure of energy-extracting magnetospheres. Within magnetospheres that exhibit differential field line bending towards both the azimuthal axis and the equatorial plane, we find that the total Poynting flux energy directed outward along the azimuthal axis can vary by over a factor of 100 for a single value of black hole spin.

astro-ph.HE↗

arXiv2019

Perturbing Monopolar Force-Free Magnetospheres to Slowly Rotating Black Holes

We study the effects of frame-dragging on the structure of force-free magnetospheres around rotating black holes. For slowly rotating black holes, analytic explorations often focus on transforming an exact force-free solution applicable to a static black hole into a solution approximately applicable to a slowly-rotating black hole via perturbations in black hole spin. We show that the single perturbed monopolar solution most commonly arrived at using such techniques is in fact a separatrix between two broad classes of solutions: those with poloidal magnetic fields that bend upwards towards the azimuthal axis and those that bend downwards towards the equatorial plane. This is because frame-dragging affects the toroidal magnetic field distributions, changing the force balance between poloidal magnetic field lines.

astro-ph.HE↗

arXiv2017

Effects of Inner Alfvén Surface Location on Black Hole Energy Extraction in the Limit of a Force-Free Magnetosphere

An energy extracting black hole magnetosphere can be defined by the location of its inner Alfvén surface, which determines the rate of black hole energy extraction along a given magnetic field line. We study how the location of the inner Alfvén surface can modify the structure of energy extracting black hole magnetospheres in the force-free limit. Hundreds of magnetospheres are numerically computed via a general relativistic extension of the Newtonian magnetofrictional method for a full range of black hole spins and flow parameters. We find that jet-like structures naturally form very close to the horizon for Alfvén surfaces near the boundary of the ergosphere and that energy is extracted towards the equatorial plane for Alfvén surfaces close to the horizon. This suggests that two broad classes of energy extracting black hole magnetospheres might exist; those that transmit extracted energy directly to distant observers, and those that transmit extracted energy to nearby accreting matter. Applied to transient high energy phenomena, we find that they might also differ in timescale by a factor of 20 or more.

astro-ph.HE↗