A quasi-linear kinetic theory for charged-particle transport in two-dimensional turbulence

There is growing evidence for the presence of a strong two-dimensional MHD turbulence component in the solar wind. The theory for energetic charged-particle transport and energization in such two-dimensional turbulence, however, is not well developed. In particular, the role of turbulent electric fields, generated by the turbulent convective motions of the two-dimensional magnetic field fluctuations, needs to be clarified. We present a new quasi-linear kinetic theory of super-Alfvenic charged-particle transport and energization in quasi-static homogeneous incompressible two-dimensional MHD turbulence, including the associated turbulent electric fields. We find for a nearly gyrotropic particle distribution that field-aligned turbulent electric fields are mainly responsible for causing particle pitch angle scattering and momentum diffusion. The new theory allows for efficient scattering through a 90degrees pitch angle whereby a long-standing problem in standard magnetostatic quasi-linear theory is addressed anew.