2021/09/06 by Luca Comisso, Lorenzo Sironi
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #Particle (ecology) #Particle acceleration #Plasma #Radiative cooling #Radiative transfer #Relativistic particle #Solar and Space Plasma Dynamics #Synchrotron #Turbulence #astro-ph.HE #astro-ph.SR #physics.plasm-ph
paper · pdf · doi:10.1103/physrevlett.127.255102
published as Phys. Rev. Lett. 127, 255102 (2021)
arxiv created 2021/09/06 · openalex created_date 2021/09/13 · openalex publication_date 2021/12/16 · arxiv updated 2022/01/03 · openalex updated_date 2026/08/06
Nature's most powerful high-energy sources are capable of accelerating particles to high energy and radiating it away on extremely short timescales, even shorter than the light crossing time of the system. It is yet unclear what physical processes can produce such an efficient acceleration, despite the copious radiative losses. By means of radiative particle-in-cell simulations, we show that magnetically dominated turbulence in pair plasmas subject to strong synchrotron cooling generates a nonthermal particle spectrum with a hard power-law range (slope p∼1) within a few eddy turnover times. Low pitch-angle particles can significantly exceed the nominal radiation-reaction limit, before abruptly cooling down. The particle spectrum becomes even harder (p<1) over time owing to particle cooling with an energy-dependent pitch-angle anisotropy. The resulting synchrotron spectrum is hard (νFν∝νs with s∼1). Our findings have important implications for understanding the nonthermal emission from high-energy astrophysical sources, most notably the prompt phase of gamma-ray bursts and gamma-ray flares from the Crab nebula.