Dominant two‐dimensional solar wind turbulence with implications for cosmic ray transport

Two new methods for distinguishing two‐dimensional (2D) turbulence from slab turbulence are applied to Helios magnetometer data. Two‐component models with varying slab and 2D ingredients are considered. Both methods indicate that solar wind magnetic turbulence possesses a dominant (∼85 % by energy) 2D component. The presence of such a large 2D component provides a natural solution to the long‐standing problem of “too small” cosmic ray mean free paths derived from quasilinear scattering theory when using the slab model.