Sub-photospheric turbulence as a heating mechanism in gamma-ray bursts

Abstract

We examine the possible role of turbulence in feeding the emission of gamma-ray bursts (GRBs). Turbulence may develop in a GRB jet as the result of hydrodynamic or current-driven instabilities. The jet carries dense radiation and the turbulence cascade can be damped by Compton drag, passing kinetic fluid energy to photons through scattering. We identify two regimes of turbulence dissipation: (1) "Viscous" - the turbulence cascade is Compton damped on a scale ${\ell }_{\mathrm{damp}}$ greater than the photon mean free path ${\ell }_{\star }$. Then turbulence energy is passed to photons via bulk Comptonization by smooth shear flows on scale ${\ell }_{\star }<{\ell }_{\mathrm{damp}}$. (2) "Collisionless" - the cascade avoids Compton damping and extends to microscopic plasma scales much smaller than ${\ell }_{\star }$. The collisionless dissipation energizes plasma particles, which radiate the received energy; how the dissipated power is partitioned between particles needs further investigation with kinetic simulations. We show that the dissipation regime switches from viscous to collisionless during the jet expansion, at a critical value of the jet optical depth which depends on the amplitude of turbulence. Turbulent GRB jets are expected to emit nonthermal photospheric radiation. Our analysis also suggests revisions of turbulent Comptonization in black hole accretion disks discussed in previous works.

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Cited by in corpus (8)

• Kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling
• Emission of magnetar bursts and precursors of neutron star mergers
• Radiative Particle-in-Cell Simulations of Turbulent Comptonization in Magnetized Black-Hole Coronae
• Structured, relativistic jets driven by radiation
• Electromagnetic Counterparts of Compact Binary Mergers
• Radiative turbulent flares in magnetically-dominated plasmas
• Ending the prompt phase in photospheric models of gamma-ray bursts
• Predicting Multiwavelength Emission Associated with X-Ray Flares and Extended Emission of Gamma-Ray Bursts