Dynamics of Two-Dimensional Solitary Vortices in a Low- β Plasma with Convective Motion

Numerical studies of the Hasegawa-Mima equation, derived in the context of drift waves but equivalent to the quasi-geostrophic vortex potential equation for Rossby waves, show the stable properties of solitary vortices which are two dimensional, localized, steady and translating solutions of this same equation. A solitary vortex can propagate only in the direction ( x -direction) perpendicular to the density gradient. When this solitary vortex solution is inclined at some angle with respect to the x -axis, its propagation direction oscillates in the x and y plane. In two dimensional collisions, i.e. head-on collision and overtaking, solitary vortices interact two-dimensionally and recover their initial shapes at the end of both types of collisions.