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

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