Electron Acceleration in the Foot Region of a Quasi-Perpendicular Shock

As reported previous AGU fall meetings, we found efficient production of non-thermal electrons in results of a three-dimensional full kinetic simulation of a quasi-perpendicular shock. What is a surprising result is that electron acceleration is observed only in 3-D simulations, and no acceleration can be seen in 1-D and 2-D simulations. In this paper, we discuss results of detailed analysis of accelerated particle trajectories. The seed acceleration occurs in large-amplitude electromagnetic wave excited in the most front region of the shock foot. A small portion of electrons keeps staying in the foot region due to the scattering by the large-amplitude electromagnetic wave, and these electrons can get energy from the motional electric field (in the shock rest frame). Since the large-amplitude electromagnetic wave is only possible in 3-D simulations, no electron acceleration is observed in previous 1-D and 2-D simulations. After the seed acceleration, these electrons can be further accelerated at the shock lamp region by the shock drift acceleration. The acceleration process occurs during the steepen phase of the self-reformation, and the acceleration efficiency depends on the phase of the shock self-reformation. We will discuss detailed physics of the seed acceleration process in the foot region.