Magnetohydrodynamic turbulence in supernova remnants

TL;DR

This paper analyzes the angular power spectra of synchrotron radiation in supernova remnants Cas A and Crab, revealing turbulence characteristics and a transition from 3D to 2D turbulence at the shell scale.

Contribution

It provides the first estimates of the angular power spectra for these remnants, linking turbulence properties to observed synchrotron fluctuations.

Findings

Power law power spectrum with index -3.24 +/- 0.03 for both remnants.

A spectral break in Cas A indicating a transition from 3D to 2D turbulence.

Consistency of the turbulence spectrum with magnetohydrodynamic turbulence models.

Abstract

We present estimates of the angular power spectra of the synchrotron radiation intensity fluctuations at 6 and 20 cm for the shell type supernova remnant Cas A and the filled-centre Crab supernova remnant. We find that the intensity fluctuations of both sources have a power law power spectrum with index -3.24 +/- 0.03. This power law power spectrum is consistent with the magnetohydrodynamic turbulence in the synchrotron emitting plasma. For Cas A, there is a break in the power spectrum and the power law index changes from -3.2 to -2.2 at large angular scale. This transition occurs at an angular scale that corresponds to the shell thickness of Cas A. We interpret this as a transition from three dimensional turbulence to two dimensional turbulence on scales that are respectively smaller and larger than the shell thickness.