Anomalous resistivity in non-Maxwellian plasmas

Abstract

Vlasov simulations of the current-driven ion-acoustic instability produced in Maxwellian and non-Maxwellian (Lorentzian, κ = 2) electron-ion plasma with number density 7 × 106 cm-3, reduced mass ratio mi/me = 25, and electron to ion temperature ratio T e/Ti = 1 are presented and compared. A concise stability analysis of current-driven ion-acoustic waves in Maxwellian and non-Maxwellian plasmas modeled by generalized Lorentzian distribution function with index 2 ≤ κ ≤ 7 and electron to ion temperature ratio 1 ≤ T e/Ti ≤ 100 is also presented. The ion-acoustic instability is excited in low temperature ratio Lorentzian (κ = 2) plasma for lower absolute electron drift velocity (up to half the critical electron drift velocity of a Maxwellian). The anomalous resistivity resulting from ion acoustic waves in a Lorentzian plasma is a strong function of the electron drift velocity and in the work presented here varies by a factor of ∼100 for a 1.5 increase in the electron drift velocity. Furthermore, ion-acoustic anomalous resistivity is excited for electron drift velocities that would be stable for Maxwellian plasmas. The magnitude of resistivity which can be generated by unstable ion-acoustic waves may be important for magnetic reconnection at the magnetopause. Copyright 2003 by the American Geophysical Union.