Counter-Streaming Beams in Collisionless Pair Plasma Instability Systems III: Collisionless Heating, Acceleration, and Radiation

Abstract

Energetic astrophysical phenomena, such as $γ$-ray bursts and supernova explosion-driven shocks in collisionless plasmas, involve various plasma kinetic instabilities, such as the Weibel instability. These systems support various types of particle acceleration and radiation through a variety of mechanisms. In this paper, we explore the energy transformations and dynamical effects of violent filament mergers seen between the large current filaments formed by the Weibel instability. The radiative processes involved in the Weibel instability filament building are also discussed in relation to jitter and synchrotron radiation.

Figures (9)

• Figure 1: Example set up of two counter streaming beams with a sinusoidal mode $\Vec{B}$ field normal to the streaming plane. The beams are composed of both positrons and electrons with $n_{e^-} = n_{e^+}$.
• Figure 2: As the beams stream into the $\Vec{B}$ field, the particles' trajectory begins ti deflect towards the nodes of the field. These particles bunches then produce the signature current filaments in the direction of flow.
• Figure 3: Field plots for $B_z$ (top left), $E$ (top right), $J$ (bottom left) and $E \cdot J$ (bottom right). The first and largest major filament merger occurs in the magnetic field and subsequent hot spots show up in the other fields. This heating hot spot is shown to be an area of particle acceleration.
• Figure 4: Various stages of isolation of the heating hot spot on the $512^2$ simulation grid (denoted by axis tick marks) . The full field is seen in the top left and a filtered region in the top right. The numerically isolated area can be seen in the bottom left. The particles that are located in these grid spots can be seen in the bottom right all converged within the box.
• Figure 5: Histograms of $\Delta\gamma_{Energy}$ for the particles within the heating region. Electrons $e^-$ are shown on the top panel of the pairs while positrons $e^+$ are below. Any difference between the particle distributions is purely circumstantial and not based on physics. The snapshot that the isolation takes place is shown in the top right, with the snapshot before it to its left and the two after below. Positive values of $\Delta\gamma_{Energy}$ confirm particle energization and acceleration.