Special Seminar: MRI turbulence in Astrophysics, Space and Laboratory Plasmas

Professor Wendell Horton
University of Texas, Austin
Thursday, May 2, 2019
11:00 am
FRH 4179
Sheared flows in magnetized plasmas are universal in astrophysics, magnetospheric, and in laboratory plasmas.  These flows produce growth of non-normal transient dynamics perturbations that evolve into nonlinear transverse cascades creating the ‘self-sustenance’ of turbulence. The linear transient dynamics being anisotropic in spectral space directly results in the anisotropic nature of nonlinear processes. This circumstance gives birth to a new type of nonlinear cascade – nonlinear transverse cascade – which is fundamentally different from the nonlinear direct and inverse cascades. Overall, the non-normal sheared flow cascades are inevitable in driven flows and are essential in determining the dynamics and transport. Both toroidal laboratory plasmas and astrophysical/Keplerian disks flows are simulated and found to have flows driven by self-sustenance of fluxes from magnetorotational instability ( MRI) turbulence and dynamo action. The MRI turbulence in the presence of compressibility generates density waves from magnetic perturbations. Understanding the MRI subcritical turbulence is important: (i) engineering flows in complex environments such as MHD winds, (ii) geophysical magnetic fields and (iii) fusion plasmas.
Zhihong Lin