Production of Nonisothermal Electrons and Langmuir Waves Because of Colliding Ion Holes and Trapping of Plasmons in an Ion Hole

We present new simulation studies exhibiting production of nonisothermal electron distributions and Langmuir waves by colliding ion holes and trapping of plasmons in an ion hole. We find that, during head-on ion hole collisions, streams of accelerated electrons are produced by the electrostatic potentials supporting the ion holes. Subsequently, Langmuir waves are excited by a two-stream instability involving energetic electron beams. The resulting Langmuir waves can be trapped in an ion hole. The present ion-hole-Langmuir wave interactions are unique kinetic phenomena which can be dealt with a Vlasov code, which we developed recently. The results can have relevance to the understanding of particle and field data that are forthcoming from different spacecraft missions in Earth’s auroral ionosphere and the magnetosphere.

Figure 1

The distribution function for the ions (left panels) and electrons (right panels) of two colliding ion holes, before the collision at times $t=0{\omega }_{p_i}$ (upper panel) and $t=35.9{\omega }_{p_i}$ (middle panel), and after the collision at $t=133{\omega }_{p_i}$ (lower panel).

Figure 2

The electron velocity distribution at $x=8r_D$, for $t=0{\omega }_{p_i}^{-1}$ (upper panel), $t=35.9{\omega }_{p_i}^{-1}$ (middle panel), and $t=133{\omega }_{p_i}^{-1}$ (lower panel).

Figure 3

The electric field at $x=8.0r_D$ as a function of ${\omega }_{p_i}t$ (left panel) and the power spectrum of the electric field as a function of $\omega /{\omega }_{p_e}$ (right panel).

Figure 4

Normalized Langmuir wave electric field $E/\sqrt{4\pi n_0{T}_i}$ (the bipolar electric field has been removed from the data) as a function of the normalized space $x/r_D$ and time ${\omega }_{p_e}t$. The Langmuir wave is trapped in the ion hole which is initially centered at $x/r_D=0$, and moving with the speed $u_0=0V_{T_i}$ (left panel) and $u_0=0.9V_{T_i}$ (right panel).