Fast dissipation of Colliding Alfvén Waves in a Magnetically Dominated Plasma

Abstract

Magnetic energy around compact objects often dominates over plasma rest mass, and its dissipation can power the object luminosity. We describe a dissipation mechanism which works faster than magnetic reconnection. The mechanism involves two strong Alfvén waves with anti-aligned magnetic fields ${\mathbf{B}}_1$ and ${\mathbf{B}}_2$ that propagate in opposite directions along background magnetic field ${\mathbf{B}}_0$ and collide. The collision forms a thin current sheet perpendicular to ${\mathbf{B}}_0$, which absorbs the incoming waves. The current sheet is sustained by electric field $\mathbf{E}$ breaking the magnetohydrodynamic condition $E<B$ and accelerating particles to high energies. We demonstrate this mechanism with kinetic plasma simulations using a simple setup of two symmetric plane waves with amplitude $A=B_1/B_0=B_2/B_0$ propagating in a uniform ${\mathbf{B}}_0$. The mechanism is activated when $A>1/2$. It dissipates a large fraction of the wave energy, $f=(2A-1)/A^2$, reaching $100\%$ when $A=1$. The plane geometry allows one to see the dissipation process in a one-dimensional simulation. We also perform two-dimensional simulations, enabling spontaneous breaking of the plane symmetry by the tearing instability of the current sheet. At moderate $A$ of main interest the tearing instability is suppressed. Dissipation transitions to normal, slower, magnetic reconnection at $A\gg 1$. The fast dissipation described in this paper may occur in various objects with perturbed magnetic fields, including magnetars, jets from accreting black holes, and pulsar wind nebulae.

arXiv comment12 pages, 10 figures, submitted to ApJ

References in corpus (11)

• Magnetars
• Fast TeV variability in blazars: jets in a jet
• Relativistic Jets Shine through Shocks or Magnetic Reconnection?
• Explosive reconnection in magnetars
• Dynamics of Strongly Twisted Relativistic Magnetospheres
• Plasmoid ejection by Alfvén waves and the fast radio bursts from SGR 1935+2154
• Dissipation of Alfvén Waves in Relativistic Magnetospheres of Magnetars
• Emission of magnetar bursts and precursors of neutron star mergers
• Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares
• Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares
• Kinetic simulations of the lowest-order unstable mode of relativistic magnetostatic equilibria

Cited by in corpus (9)

• Weak Alfvénic turbulence in relativistic plasmas II: Current sheets and dissipation
• Relativistic Alfvén Waves Entering Charge Starvation in the Magnetospheres of Neutron Stars
• Radiative pulsar magnetospheres: oblique rotators
• Force-free wave interaction in magnetar magnetospheres: Computational modeling in axisymmetry
• An Intermediate-field Fast Radio Burst Model and the Quasi-periodic Oscillation
• Exact nonlinear solutions for three-dimensional Alfvén-wave packets in relativistic magnetohydrodynamics
• Breakdown of force-free electrodynamics in electric zones
• Particle acceleration by counter-propagating circularly polarized Alfvén waves
• Heating of Magnetically Dominated Plasma by Alfvén-Wave Turbulence