Asymmetric Diffusion of Magnetic Field Lines
  Stochasticity of magnetic field lines is important for particle transport
properties. Magnetic field lines separate faster than diffusively in turbulent
plasma, which is called superdiffusion. We discovered that this superdiffusion
is pronouncedly asymmetric, so that the separation of field lines along the
magnetic field direction is different from the separation in the opposite
direction. While the symmetry of the flow is broken by the so-called imbalance
or cross-helicity, the difference between forward and backward diffusion is not
directly due to imbalance, but a non-trivial consequence of both imbalance and
non-reversibility of turbulence. The asymmetric diffusion perpendicular to the
mean magnetic field entails a variety of new physical phenomena, such as the
production of parallel particle streaming in the presence of perpendicular
particle gradients. Such streaming and associated instabilities could be
significant for particle transport in laboratory, space and astrophysical
plasmas.
