Spectral curvature and breaks from Fermi acceleration at oblique shocks

2025/11/03 by Asma Shirin T, T, Asma Shirin, Brian Reville +7 · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Solar and Space Plasma Dynamics #Astrophysical Phenomena and Observations

paper · pdf · doi:10.48550/arxiv.2511.01635

Abstract

A major attraction of diffusive shock acceleration is the prediction of power-law spectra for energetic particle distributions. However, this property is not fundamental to the theory. We demonstrate that for planar shocks with an oblique magnetic field the generation of power-law spectra critically requires the particles' scattering rate to be both directly proportional to their gyro radius (Bohm scaling) and spatially uniform. Non-Bohm scaling results in curved spectra at oblique shocks, while abrupt changes in the spatial profile of the scattering upstream introduces spectral breaks. Using the publicly available code Sapphire++, we numerically explore the magnitude of these effects, which are particularly pronounced at fast shocks, as expected in active galactic nuclei and microquasar jets, or young supernova remnants.

Citations

• The polarization of the synchrotron radiation from a recollimated jet: application to high-energy BL Lacs
• Using Spherical Harmonics to solve the Boltzmann equation: an operator based approach
• The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope -- Data Release 2

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