Trans-Alfvenic Magnetohydrodynamic Turbulence in the Vicinity of Supernova Remnant Cassiopeia-A Shocks

TL;DR

This study measures magnetic energy spectra around supernova remnant Cassiopeia-A, revealing trans-Alfvenic magnetohydrodynamic turbulence and magnetic field amplification near shocks, consistent with theoretical predictions.

Contribution

It introduces a new unbiased method to measure magnetic energy spectra in SNRs, confirming the presence of trans-Alfvenic turbulence and magnetic field amplification near shocks.

Findings

Magnetic energy spectra follow a 2/3 power law over a decade of scales.

Results support the presence of trans-Alfvenic turbulence near SNR shocks.

Magnetic field amplification occurs within ~0.115pc of the shocks.

Abstract

Statistics of the magnetic field disturbances in the supernova remnants (SNRs) can be accessed using the second-order correlation function of the synchrotron intensities. Here we measure the magnetic energy spectra in supernova remnant Cassiopeia-A by two-point correlation of the synchrotron intensities, using a recently developed unbiased method. The measured magnetic energy spectra in the vicinity of supernova remnant shocks are found to be 2/3 power law over the decade of range scales, showing the developed trans-Alfvenic magnetohydrodynamic turbulence. Our results are globally consistent with the theoretical prediction of trans-Alfvenic Mach number in developed magneto-hydrodynamic turbulence and can be explained by the amplification of the magnetic field in the vicinity of SNR shocks. The magnetic energy spectra predict SNR Cassiopeia-A having an additional subshock in the radio frequency observation along with forward and reverse shocks, with a radial window of the amplified magnetic field of ~ 0.115pc near the shocks