Generation of poloidal magnetic field in a hot collisional plasma by inverse Faraday effect

Abstract

Generation of poloidal magnetic field in a hot and collisional plasma by an inverse Faraday effect is discussed. This field can either be induced by a circularly polarized laser beam (CPLB) or a plane-polarized laser beam (PPLB). For the CPLB, an average field 〈ℜx〉∼I0λ∼11.6 MG could be produced in a DT plasma for a high intensity (I0=1022 W/m2) and shorter wavelength (λ=0.35 μm) laser. This field is essentially induced by the field inhomogeneity effect and dominates over that induced by the plasma inhomogeneity effect (〈ℜx〉∼I2/30λ7/3∼2.42 MG). The collisional and thermal contribution to 〈ℜx〉 is just negligible for the CPLB. However, in the case of PPLB the poloidal field is generated only for a hot and collisional plasma and can be quite large for a longer wavelength laser (e.g., CO2 laser, λ=10.6 μm). The collisional effect induces a field 〈ℜx〉∼0.08 kG, which dominates near the turning point and is independent of the laser parameters. However, in the outer cronal region the thermal pressure effect dominates (e.g., 〈ℜx〉∼I5/30λ4/3∼3.0 MG). Further, 〈ℜx〉 for the p-polarized beam is, in general, relatively smaller than that for the s-polarized beam. Practical implications of these results and their limitations are discussed.