Speaker
Description
We perform extensive test-particle simulations of cosmic rays (CRs) propagating in synthetic (homogenous and isotropic) turbulent magnetic fields using the Monte Carlo code CRPropa. Applying multiple numerical methods in the literature, we compute the coefficients of the diffusion tensor as a function of particle rigidity and turbulence level, i.e. the ratio between the root mean square of the turbulent component and the magnitude of the uniform field. With the Taylor-Green-Kubo (TGK) formalism, we find the timescales of decorrelation of particle directions to directly compute the diffusion coefficients. We study the different rigidity-dependence of the perpendicular coefficient to the predicted power-law in the quasi-linear theory framework. Moreover, with the TGK approach we are able to calculate the antisymmetric coefficient for low turbulence scenarios and find evidence of a linear dependence on rigidity. As it is predicted that antisymmetric diffusion might be connected to the appearance of drift velocities, we propose the analysis of the corresponding escape timescale for cosmic rays. We discuss the energy of relevance of this effect in galactic CRs and its potential role for the galactic-extragalactic transition of CRs.
