Amplification of magnetic field at inward shocks of supernova remnant Cassiopeia A (speaker: Federico Fraschetti, Universit of Arizona
Multi-epoch X-ray observations of Supernova Remnants (SNRs) are crucial to probe the presence of accelerated electrons at shocks and the observed rapid variability has been long indicating a magnetic field far exceeding the theoretically predicted strength by the compression of the shock alone. Within the SNR Cassiopeia A, joint Chandra and NuSTAR observations recently allowed to single out six inward moving shocks arguably originated from the collision of the forward shock with a molecular cloud in the interstellar medium. Such shocks exhibit an unexpected variability (both increase and decrease) of the flux up to 50% on timescale of a few years. We show that such variability can be interpreted as the result of small-scale dynamo amplifying the magnetic field at astrophysical shocks, demonstrating for the first time that the unfolding of a dynamo process formerly theoretically identified can be observed in astrophysical systems.