Click here for a 1.1MB MPEG movie showing a time series of the measured 2D magnetic field vectors produced by the constructive interference of two Alfvén cones. The wave vectors lie in a plane perpendicular to the background magnetic field. The plane measures approximately 10cm in x and 9cm in y, and was sampled on an irregularly-spaced 21x16 grid for a total of 336 data points. Both arrow length and color indicate the magnitude of the vector (black is zero field, blue is about 10 mGauss, and red is about 40 mGauss.) The frequency of the wave is 200KHz, and the ion-cyclotron frequency is 380KHz.
Click here for a 1.9MB MPEG movie showing a comparison between theory and experiment of the 2D magnetic field vectors produced by the destructive interference of two Alfvén cones. The data were taken in the same spatial locations as in the constructive interference case, and the theoretically-predicted vectors were calculated at the x-y positions which match those of the experiment. The phase of the signal applied to each disk exciter differed by 20 degrees. This phase imbalance can be seen in the experimental data and in the theory. It manifests itself as a shifting in space and time of the position of the central minimum in the wave pattern.
These amplitude profiles were computed numerically from
, is also found numerically
by solving the dispersion relation:
,
is the
electron thermal velocity, 
is the derivative with respect to the argument of the plasma dispersion function,
and 
(
).