Adiabatic non-resonant acceleration in magnetic turbulence and hard spectra of gamma-ray bursts

27 Aug 2017  ·  Xu Siyao, Zhang Bing ·

We introduce a non-resonant acceleration mechanism arising from the second adiabatic invariant in magnetic turbulence and apply it to study the prompt emission spectra of gamma-ray bursts (GRBs). The mechanism contains both the first- and second-order Fermi acceleration, originating from the interacting turbulent reconnection and dynamo processes... It leads to a hard electron energy distribution up to a cutoff energy at the balance between the acceleration and synchrotron cooling. The sufficient acceleration rate ensures a rapid hardening of any initial energy distribution to a power-law distribution with the index $p \sim 1$, which naturally produces a low-energy photon index $\alpha \sim -1$ via the synchrotron radiation. For typical GRB parameters, the synchrotron emission can extend to a characteristic photon energy on the order of $\sim 100$ keV. read more

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High Energy Astrophysical Phenomena High Energy Physics - Theory Plasma Physics