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Keywords:

  • MHD;
  • radiation mechanisms: non-thermal;
  • relativistic processes;
  • shock waves;
  • supernova remnants;
  • gamma-rays: ISM

ABSTRACT

Very high energy gamma-ray flares from the Crab nebula detected by the AGILE and Fermi satellites challenge our understanding of the pulsar wind nebulae. The short duration of the flares, only a few days, is particularly puzzling since it is much shorter than the dynamical time-scale of the nebula.

In this work we investigate analytically and via numerical simulations the electromagnetic signatures expected from the large-amplitude low-frequency magnetosonic waves generated within the Crab nebula which induce the corrugation perturbations of the termination shock. As a result, the oblique termination shock produces a time-dependent, mildly relativistic post-shock flow. Using the relativistic magnetohydrodynamic version of the riemann code, we simulate the interaction of the termination shock with downstream perturbations. We demonstrate that mild Doppler boosting of the synchrotron emission in the post-shock flow can produce bright, short time-scale flares.