Efficiency of proton-driven Weibel instability at thermalizing initially two-temperature astrophysical plasmas

Whether an efficient collisonless temperature equilibration mechanism exists for a two-temperature ion-electron plasma, with $T_i>T_e$, is important for understanding astrophysical phenomena such as radiatively inefficient accretion flows and supernova remnants. Here we study whether Weibel instability driven by a proton temperature anisotropy can be such a mechanism. Analysis and PIC simulations find that in an unmagnetized plasma, although the instability grows at a rate much larger than the ion-electron collision rate, the saturated magnetic field is low and inefficient to couple the ions and electrons. It is speculated that in a magnetized plasma the instability can provide a more efficient coupling.