Collisionless Heating Driven by Vlasov Filamentation in a Counterstreaming Beams Configuration

We perform high resolution kinetic simulations of interpenetrating plasma beams. This configuration is unstable to both Weibel-type and two-stream instabilities, which are known to linearly induce a growth of the magnetic and electrostatic energy, respectively, at the expenses of the kinetic energy. "Oblique modes" are further beam-plasma instabilities, which linearly combine the features of the former two. Here we show the possibility of a reversal of the energy flow associated to these beam-plasma instabilities, when secondary propagating oblique modes are excited. This rapid conversion from magnetic to kinetic energy (i.e., kinetic heating), differs from the standard magnetic reconnection scenario and is induced by the reinforcement of the filamentation process of the distribution function in the phase space. This phenomenon-likely of general interest to collisionless dissipation processes in plasmas-can be understood in terms of mode synchronization: the coupling of oblique modes at disparate spatial scales leads to the appearance of synchronized "filamented" modes, which act on the global dynamics of the plasma via kinetic heating, collisionless dissipation, and turbulence.