Switch-On Shock applet:

===>Uses the Crank-Nicholson method to integrate the DNLSB.  Appears to be accurate and efficient.  Adjust the "Courant parameter", C = Dt/Dx, to take a bigger time step.  For C too big, numerical instability occurs.  

===>The dispersion, R, and dissipation, Rbar, can be adjusted through the applet interface.  The numerical result for the y-component of the magnetic field is in black and the x-comp. is in green.  This is plotted over the exact solution which has the y-comp. as dark gray and the x-comp. as dark green.  These seem to coincide well.

===>Included for starters is the simple perturbing effect "Gb" with G = Gr + Gi.  This  is set to zero by default.  A simple linear analysis shows Gr positive to lead to an exponential growth of the wave amplitude and Gi to lead to a faster wave speed.  Take values of these to be quite small ... ~ 0.001 or smaller.  Larger values quickly lead to a violation of the assumed boundary conditions.

===>Some things that might be interesting/amusing to check:  interaction of the S-O Shock with other waves, changing the numerical frame of reference to that of the shock, adding a periodic (or stochastic?) driver, seeing how the shock adapts if the dispersion or dissipation is adjusted (separately from the values which define the shock structure) ...

 

 

  Background Material for Richter Proposal
Online: A low beta Alfven shock,

Introduction to bowshocks & related issues,  

Alfven waves etc., 

Jupiter's moon Io, [search for "Alfven"]

Background: Read the introductions as time permits.
Hannes Alfven: Bio sketch at LANL
Background & related research & work Background   ... for a visual demonstration of the relation between the stability of a one-dimensional wave and transverse effects (which we will study for the Alfven Switch-On Shock and the Intermediate Alfven shock, look at the link to "A KdV Soliton at Work":  a highly turbulent 2D mess is transformed into a pristine 1D wave traveling in front of the boat.  Presumably this wave would be stable with respect to certain transverse effects.  It would be very useful to know if the 1D Alfven shocks have a similar property.

Coronal Mass Ejection:  

Alfven Soliton Research:  

Jim Honea's work:  numerical methods applied to nonlinear PDE's

Jacob Barber's work: 3D Alfven shocks & visualization

 
Comments: Robert Hamilton, rhamilton@georgefox.edu