Interactions of isolated vortices I: Modons colliding with modons

Collisions between isolated(i.e. localized) dipolar vortex states, called modons, are examined in various numerical solutions of the quasigeostrophic, equivalent barotropic equation. For a range of parameters, the collision interactions are soliton-like in that the vorticity maxima are displaced (phase-shifted) with only small speed changes and little excitation of internal degrees of freedom. For other parameters, new “inelastic” effects are observed, including speed changes due to vorticity rearrangement, vorticity filamentation, modon “capture” or “fusion” in an overtaking collision, and the “fission” of a modon into its component vorticity monopoles in a head-on collision.