The Expansion and Width of the Synchrotron Filaments Associated with the Forward Shock of Cas A

X-ray observations of Cas A have revealed filamentary non-thermal rims tracing the forward shock of the supernova remnant (SNR). These structures have been identified as synchrotron radiation from shock-accelerated electrons with TeV energies, interacting with the compressed, and probably amplified, local magnetic field. Magnetic field amplification (MFA) is broadly believed to result from, and contribute to, cosmic ray acceleration at the shocks of SNRs. Using data from the long term Chandra program studying the evolution of Cas A, we have estimated the expansion of the non-thermal rims at the forward shock of the SNR, as well as the width of these filaments. Since the size of the synchrotron filaments places constraints on the magnetic field strength, this study allows us to establish a connection between the shock velocity and the characteristics of the particle acceleration process.