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 κ̄ = (b̄/r_c)/√2, where r_c = √T/m/Ω_c is the cyclotron radius and b̄ = 2e ²/T is twice the distance of closest approach. For a strongly magnetized plasma (i.e., κ̄ ≫ 1), the equipartition rate is exponentially small (v∼exp[ -5(3πκ̄)2/5/6]). For a weakly magnetized plasma (i.e., κ̄ ≪ 1), the rate is the same as for an unmagnetized plasma except that r_c/b̄ replaces λ_D/b̄ in the Coulomb logarithm. (It is assumed here that r_c < λ_D; for r_c > λ_D, the plasma is effectively unmagnetized.) This paper contains a numerical treatment that spans the intermediate regime κ̄∼1, and connects onto asymptotic results in the two limits κ̄ ≪ 1 and κ̄ ≫ 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 κ̄ and four decades in the scaled rate v/nv̄b̄², where n is the electron density and v̄ = √2T/m.