Quasi‐linear Drift of Cosmic Rays in Weak Turbulent Electromagnetic Fields

A general quasilinear transport parameter for particle drift in arbitraryturbulence geometry is presented. The new drift coefficient is solelycharacterized by a nonresonant term and is evaluated for slab andtwo-dimensional turbulence geometry. The calculations presented heredemonstrate that fluctuating electric fields are a key quantity forunderstanding quasilinear particle drift in slab geometry. It is shown thatparticle drift does not exist in unpolarized and purely magnetic slabfluctuations. This is in stark contrast to previous models, which arerestricted to slab geometry and the field line random walk limit. Theevaluation of the general transport parameter for two-dimensional turbulencegeometry, presented here for the first time for dynamical magnetic turbulence,results in a drift coefficient valid for a magnetic power spectrum andturbulence decay rate varying arbitrarily in wavenumber. For a two-component,slab/two-dimensional turbulence model, numerical calculations are presented.The new quasilinear drift, induced by the magnetic perturbations, is comparedwith a standard drift expression related to the curvature and gradient of anunperturbed heliospheric background magnetic field. The considerationspresented here offer a solid ground and natural explanation for the hithertopuzzling observation that drift models often describe observations much betterwhen drift effects are reduced.Comment: 23 pages, 6 figures, accepted for publication in Ap