The electron-acoustic mode

Abstract

This paper examines electrostatic modes in an unmagnetized, homogeneous, Vlasov plasma with three Maxwellian components: ions, hot electrons, and cool electrons. In such a plasma, the electron‐acoustic mode with frequencies between the ion and electron plasma frequencies may propagate with light damping. The conditions that allow propagation of this mode, which is distinct from the well‐known ion‐acoustic and Langmuir waves, are given in detail; approximate necessary conditions are 10≲T_h/T_c and 0<n_cn_e, where the subscripts c, h, and e refer to the cool and hot electron components and the total electron population, respectively.