Superspirals of compression arising from a meandering motion of the primary spiral

The effect of a meandering two-frequency motion of the core of a primary Archimedean spiral on the shape in the farfield is illustrated. Different pictures correspond to different parameter values. The motion of the core results in a change of the local wavenumber in the farfield. The apparent pattern consists of an underlying almost Archimedian spiral and a superimposed large spiral wave. In the first picture, the superimposed spiral is oriented in the same direction as the primary spiral. In the last picture, it takes the opposite orientation. At the transition, the superimposed spiral degenerates to a sector. The superimposed patterns consist of dark regions where the wavelength of the primary spiral is shorter than the average, and bright regions of larger wavelength. The effect is enhanced by a convolution-type image processing.

Drifting superspiral: Farfield picture of a spiral at 1:1-resonant drift. The superspiral degenerates into a sector of compressed waves.

Outward meandering superspiral: Farfield picture of the superspiral formed by a meandering spiral wave with outward directed petals. Primary spiral and superspiral have opposite orientations.

Inward meandering superspiral: Farfield picture of the superspiral formed by a meandering spiral wave with inward directed petals. Primary spiral and superspiral have the same orientation.