MHD Turbulence and Cosmic Rays

The Universe is filled with ionized plasma, that can be described by magnetohydrodynamics (MHD) on large scales and high energy particles called cosmic rays. It turns out that cosmic rays are dynamically important in many environments, such as the disk of our Galaxy. We also understand that cosmic ray acceleration in shocks must necessarily involve MHD turbulence produced by CRs in front of the shock. MHD turbulence by itself is an extremely exciting subject which allowed us to formulate some new universality claims regarding its spectral properties and time evolution. Not surprisingly, the interaction of MHD turbulence with cosmic rays is even more interesting and I will be talking about some work in progress and some new tools that we are developing in this direction.