[GTP] GTP Seminar at NCAR---Ed Lee

[Silvia Gentile]

Comparison of three classes of symmetric MHD decay flow simulations with 
high resolution DNS

Ed Lee
Turbulence Numerics Team, IMAGe (NCAR)
January 21 at  2pm
FL2-Rm 1001


Three different MHD decay flows displaying Taylor-Green-type symmetries 
are computed at high resolution using an efficient, parallel, spectral 
code customized to exploit the flow symmetries without loss of accuracy. 
Different phenomenological behavior is identified for the three classes 
of flows, where the occurrence of Alfven waves, micro-instabilities, and 
dynamic alignment are found to be dependent on initial conditions, which 
determine characteristic time scales, such as the Alfven and eddy 
turnover times.  All of the flows are three-dimensional and deliberately 
quasi-isotropic to better understand small-scale behavior in the absence 
of a mean magnetic field.  Strong background magnetic fields, common in 
geophysical and astrophysical plasma environments, are known to suppress 
energy transfer in the parallel direction and therefore may limit the 
dynamical possibilities of MHD.  In this study, both isotropic and 
anisotropic tools are used to assess and interpret the physics of the 
flows, which are postulated to be unchanged by the symmetries 
implemented in the code.