Comparison of Weibel Instability and Magnetic Field Generating Thermal Instability

抄録

Comparison of the mechanisms of the Weibel instability and the field generating thermal instability is made on the basis of the Boltzmann equation. The case k⊥∇T₀⁄⁄∇n₀ is investigated, where k is the wave vector, T₀ and n₀ are the zeroth order temperature and the number density. In the collisional plasma (kl_m<<1, where l_m is the electron mean free path), the thermal instability is unstable, but the Weibel instability is stable. In the collisionless case (kl_m>>1), the situation is vice versa. When the equilibrium velocity distribution function is expanded by the Legendre polynomials P_l with the polar axis along ∇T₀, l=2 and l=1 components are essential, respectively, for the Weibel instability and the thermal instability.