Fermi Gamma-ray Space Telescope

Time-Dependent Electron Acceleration in Pulsar Wind Termination Shocks: Application to the 2007 September Crab Nebula Gamma-ray Flare

Justin Finke
(John Kroon, Peter Becker)


We recently developed a time-dependent analytical model describing acceleration and energy losses for a population of electrons in the vicinity of a pulsar wind termination shock. In this model, synchrotron emission is produced by magnetically-confined blobs of electrons in the upstream wind. Shock-induced magnetic reconnection creates strong electrostatic fields that can accelerate particles beyond the radiation reaction limit. As the blob passes through the shock the dominant particle escape mechanism changes from diffusive to adiabatic escape. We apply our model to the flaring activity detected from the Crab Nebula by AGILE in 2007 September. We demonstrate that our model can reproduce the W1 wave and F2 sub-flare, the two events from this epoch with the best data. We found that the 2007 September events required about half the total expended energy as the 2011 April Crab Nebula sub-flares (which we previously modeled) and had electric and magnetic field strengths comparable to the 2011 event.