COLLISIONAL EQUIPARTITION RATE FOR A MAGNETIZED PURE ELECTRON-PLASMA

The collisional equipartition rate between the parallel and perpendicular velocity components is calculated for a weakly correlated electron plasma that is immersed in a uniform magnetic field. Here, parallel and perpendicular refer to the direction of the magnetic field. The rate depends on the parameter kappa-BAR = (bBAR/r(c))/square-root 2, where r(c) = square-root T/m/OMEGA(c) is the cyclotron radius and bBAR = 2e2/T is twice the distance of closest approach. For a strongly magnetized plasma (i.e., kappa-BAR much greater than 1), the equipartition rate is exponentially small (nu approximately exp[- 5(3-pi-kappa-BAR)2/5/6]). For a weakly magnetized plasma (i.e., kappa-BAR much less than 1), the rate is the same as for an unmagnetized plasma except that r(c)/bBAR replaces lambda(D)/bBAR in the Coulomb logarithm. (It is assumed here that r(c) < lambda(D); for r(c) > lambda(D), the plasma is effectively unmagnetized.) This paper contains a numerical treatment that spans the intermediate regime kappa-BAR approximately 1, and connects onto asymptotic results in the two limits kappa-BAR much less than 1 and kappa-BAR much greater than 1. Also, an improved asymptotic expression for the rate in the high-field limit is derived. The present theoretical results are in good agreement with recent measurements of the equipartition rate over eight decades in kappa-BAR and four decades in the scaled rate nu/nubBAR2, where n is the electron density and u-BAR = square-root 2T/m.