Proton resonant firehose instability: Temperature anisotropy and fluctuating field constraints

摘要: The electromagnetic proton firehose instability may grow in a plasma if the velocity distribution is approximately bi-Maxwellian and T‖p > T⊥p, where directional subscripts denote directions relative to background magnetic field. Linear Vlasov dispersion theory homogeneous electron-proton implies an threshold condition at constant maximum growth rate 1 − T⊥p/T‖p = Sp/β‖pαp over < β‖p ≤ 10 Bo Here Sp αp are fitting parameters ≃ 0.7. One- two-dimensional initial value hybrid simulations of this growing mode carried out under cyclotron resonant conditions on domain 2 ≲ 100. show that enhanced fluctuations from impose bound temperature anisotropy form above equation with fluid result 1.0. On both one- yield new for upper fluctuating field energy density SB αB empirical which functions rate. This logarithmic behavior qualitatively different prediction and, like bound, should be subject observational verification any sufficiently bi-Maxwellian.