[P-EM16] Space Plasma Physics: Theory and Simulation

[PEM16-09] Linear analysis of chiral plasma instability in uniform magnetic fields

Kei Nishida¹, *Takahiro Miyoshi¹ (1.Graduate School of Advanced Science and Engineering, Hiroshima University)

Keywords:chiral plasma instability, chiral magnetohydrodynamics, linear analysis

In extreme environments such as the very early universe and high-energy heavy-ion collisions, the exsistence of a chirally imbalanced medium is theoretically predicted, in which the number densities of right-handed and left-handed fermions are imbalanced. In the chirally imbalanced medium, it is expected that the chiral magnetic effect (CME), which transports a non-dissipative electric current along a magnetic field, is generated. On the other hand, the macroscopic behavior of electrically charged particles is governed by magnetohydrodynamics (MHD). In order to elucidate the macroscopic behavior of the chirally imbalanced medium, theoretical and simulation studies of chiral MHD including the CME have been in progress in recent years [e.g., Rogachevskii et al. 2017; Masada et al. 2018]. Yet, we poorly understand chiral MHD, even its linear instabilities. Therefore, the purpose of this study is to reveal the chiral plasma instability [Akamatsu and Yamamoto, 2013] in uniform magnetic fields using linear analysis of resistive chiral MHD equations.

In the chiral plasma instability, fluctuations of the magnetic field are enhanced by the positive feedback between the non-dissipative current due to the CME and the magnetic field induced by its current. In resistive chiral MHD, the CME competes with resistive diffusion, and only modes lower than a critical wavenumber grow. Furthermore, in a system with a background magnetic field, the fluctuations of the magnetic field are coupled to the equation of motion via the background magnetic field. In particular, focusing on the Lundquist number S, we performed the linear analysis for modes parallel and perpendicular to the background uniform magnetic field. For simplicity, we assume here that the chiral imbalance is uniform in space and time. The results showed that the parallel modes have an unstable region at any S, while the perpendicular modes are completely stabilized above a certain S.

References:
I. Rogachevskii et al., Astrophys. J., 846:153 (2017)
Y. Masada et al., Phys. Rev. D98, 083018 (2018)
Y. Akamatsu and N. Yamamoto, Phys. Rev. Lett. 111, 052002 (2013)