| Collisionless magnetic reconnection requires the violation of ideal MHD by various
kinetic-scale effects. Recent research has highlighted the potential importance of
wave-particle interactions by showing that Vlasov simulations of unstable ion-acoustic waves
predict an anomalous resistivity that can be significantly higher in the nonlinear regime than
the quasi-linear estimate. Here, we investigate the dependence on the initial electron drift
velocity of the current driven ion-acoustic instability and its resulting anomalous resistivity.
We examine the properties of statistical ensembles Vlasov simulations with real mass ratio
for a range of drift velocities and for electron to ion temperature ratios relevant to both solar
and magnetospheric physics. We show that the ion-acoustic anomalous resistivity depends
nonlinearly on the electron drift velocity for the low temperature ratios examined, in contrast
to the linear dependence predicted by theory and commonly assumed in models of
magnetic reconnection. We examine the dependence of resistivity on the electron to ion
temperature ratios. An anomalous resistivity model consistent with our results could
be important for simulations of magnetic reconnection in astrophysical plasmas. |