14:30 〜 14:45
[PEM17-09] Turbulences and heating in weakly magnetized, perpendicular shocks in the transrelativstic regime.
キーワード：Space Plasma, Instabilities, Gamma-ray bursts
Gamma-ray bursts (GRB) events are associated with relativistic shocks. The prompt emission is usually associated with internal, possibly mildly relativistic, shocks. There, a considerable amount of energy mostly carried by ions, can be converted into radiating high-energy electrons. While the detailed acceleration mechanism of the radiating population is debated, how the shock-energy is dissipated otherwise remains unclear. In the case of the ultra-relativistic shock-front decelerating in the interstellar medium, also associated the with the long-lasting "Afterglow" emission, detailed analysis of the spectrum and dedicated simulations bring out the possibility that significant energy is converted by heating the electrons in turbulence ahead of the shock.
It is unknown how varying Lorentz factor may affect the pre-heating and particle acceleration of a quasi-perpendicular shock. In this context, many unstable modes can grow at the same time, and it is not obvious which one will govern the dynamics of the plasma.
To clarify the situation, an overview of shock-driven kinetic instabilities is presented. Analytical estimates of the growth rates and typical coherence length over the transrelativistic regime are derived to determine the early linear evolution of the system. Relativistic beaming of a reflected population of ions is shown to affect the growth of electromagnetic modes. Heating of the plasma is shown to occur first in self-regulating electrostatic oblique modes, while turbulent electric fields propagating along the beam axis offer a persistent source of parallel heating, beneficial for the development of electromagnetic modes. The implications of saturation beyond the linear regime are discussed.
It is unknown how varying Lorentz factor may affect the pre-heating and particle acceleration of a quasi-perpendicular shock. In this context, many unstable modes can grow at the same time, and it is not obvious which one will govern the dynamics of the plasma.
To clarify the situation, an overview of shock-driven kinetic instabilities is presented. Analytical estimates of the growth rates and typical coherence length over the transrelativistic regime are derived to determine the early linear evolution of the system. Relativistic beaming of a reflected population of ions is shown to affect the growth of electromagnetic modes. Heating of the plasma is shown to occur first in self-regulating electrostatic oblique modes, while turbulent electric fields propagating along the beam axis offer a persistent source of parallel heating, beneficial for the development of electromagnetic modes. The implications of saturation beyond the linear regime are discussed.