Turbulence theory

This page includes:

Progress log | Plots |

and link to MHD related papers

December 2005:
  1. computed anisotropic power spectrum
  2. implemented alfvenic (also incompressible) driving [as an option]
     in addition to the original isotropic incompressible driving
  3. implemented damping of velocity component along mean B-field [controlled by a parameter]
  4. modified driving normalization and time interval


To do list:
  1. quantify anisotropy (half done)
  2. implement 1-directional (inbalanced) Alfvenic driving
  3. calculate oscillation frequency
  4. implement relative Alfven-fast driving

Common parameters
  MHD equations: isothermal;
                 sound speed cs=1
  initial condition:
      uniform density rho0=1;
      uniform B-field in positive z-direction with Alfven speed va=10
  driving: new acceleration field is generated every eddy turnover time,
	   a velocity perturbation, dv=accel*(advection time step),
	   is added to the fluid at each fluid update;
           dv has power spectrum v(k)=k**6 * exp(-4.*(k/kpk)**2)
           and kpk at half the simulation box size;
           normalized by an overall constant to give a turbulence
	   velocity around 0.5
  plots: The (anisotropic) power spectrums are computed following the
         method of Cho and Lazarian, and are presented below as log10
	 contour plots

Specific runs
  1. n=64, no v-damping, isotropic incompressible driving
     driving power spectrum (only Alfven mode is shown because the other modes are similar)
     density power spectrums
     Alfven mode velocity power spectrums
     fast mode velocity power spectrums
     slow mode velocity power spectrums
  2. n=64, no v-damping, alfvenic driving
     driving power spectrums
     density power spectrums
     Alfven mode power spectrums
     fast mode power spectrums
     slow mode power spectrums
  3. n=128, no v-damping, isotropic incompressible driving
     driving power spectrum (only Alfven mode is shown because other modes are similar)
     density power spectrums
     Alfven mode power spectrums
     fast mode power spectrums
     slow mode power spectrums
  4. n=128, no v-damping, alfvenic driving
     driving power spectrums
     density power spectrums (suppressed and very anisotropic)
     Alfven mode power spectrums
     fast mode power spectrums
     slow mode power spectrums (suppressed and very anisotropic)

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