Coronal heating by fast dissipation of Alfven waves in 3D magnetic fields

The dissipation of a large number of Alfven wave packets propagating in an inhomogeneous 3-D magnetic field is numerically studied in the WKB approximation. The dissipation rate is found to scale proportional to the logarithm of viscosity and/or resistivity. This phenomenon is related to the exponential separation of neighbouring rays; estimations of the corresponding rate are consistent with the behaviour of the Kolmogorov entropy in this kind of structures. The scaling law t(d) proportional to ln S does hold not only in an irregular magnetic field, but it is verified also in quasi-uniform magnetic structures, which contain very small chaotic regions.