Jonathan Zrake

PRODUCING MAGNETAR MAGNETIC FIELDS IN THE MERGER OF BINARY NEUTRON STARS

The merger of binary neutron stars (BNSs) can lead to large amplifications of the magnetic field due to the development of turbulence and instabilities in the fluid, such as the Kelvin-Helmholtz shear instability, which drive small-scale dynamo activity. In order to properly resolve such instabilities and obtain the correct magnetic field amplification, one would need to employ resolutions that are currently unfeasible in global general relativistic magnetohydrodynamic (GRMHD) simulations of BNS mergers. Here, we present a subgrid model that allows global simulations to take into account the small-scale amplification of the magnetic field which is caused by the development of turbulence during BNS mergers. Assuming dynamo saturation, we show that magnetar-level fields (

INVERSE CASCADE OF NONHELICAL MAGNETIC TURBULENCE IN A RELATIVISTIC FLUID

\sim 10^{16}\,{\rm G}

CRAB FLARES DUE TO TURBULENT DISSIPATION OF THE PULSAR STRIPED WIND

) can be easily reached, and should therefore be expected from the merger of magnetized BNSs. The total magnetic energy can reach values up to

Freely decaying turbulence in force-free electrodynamics

\sim 10^{51}\,{\rm erg}

Spontaneous Decay of Periodic Magnetostatic Equilibria

and the post-merger remnant can therefore emit strong electromagnetic signals and possibly produce short gamma-ray bursts.

Ab Initio Simulations of a Supernova-driven Galactic Dynamo in an Isolated Disk Galaxy

The free decay of nonhelical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum PM (k, t) is self-similar in time and well modeled by a broken power law with subinertial and inertial range indices very close to 7/2 and –2, respectively. The magnetic coherence scale is found to grow in time as t 2/5, much too slow to account for optical polarization of gamma-ray burst afterglow emission if magnetic energy is to be supplied only at microphysical length scales. No bursty or explosive energy loss is observed in relativistic MHD turbulence having modest magnetization, which constrains magnetic reconnection models for rapid time variability of GRB prompt emission, blazars, and the Crab nebula.

Simplex-in-cell technique for collisionless plasma simulations

We interpret

Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

\gamma

Magnetic Field Generation in Stars

-ray flares from the Crab Nebula as the signature of turbulence in the pulsars electromagnetic outflow. Turbulence is triggered upstream by dynamical instability of the winds oscillating magnetic field, and accelerates non-thermal particles. On impacting the wind termination shock, those particles emit a distinct synchrotron component

Kinetic simulations of the lowest-order unstable mode of relativistic magnetostatic equilibria

F_{\nu,\rm flare}