Simulations of second-order Fermi acceleration of electrons: solving the injection problem

The boosting of electrons from a Maxwellian distribution into a suprathermal power-law tail is studied, using a test-particle simulation code, following the full equations of motion of tens of thousands of electrons chosen from a thermal population as they move through general time-dependent magnetic fields. This distinguishes between bulk heating of the electron population or boosting of selected electrons. Which of these occurs is found to depend on the size of the swarm thermal speed compared with the electron thermal speed