Aggregation of vortex structures in 2D: the blob-wave system and its role in zonal flows (2505.22700v1)

Abstract: We give a rigorous mathematical result, supported by accurate numerical simulations, of the aggregation of a concentrated vortex blob with an underlying non constant vorticity field: the blob moves in the direction of the gradient of the field. It is a unique example of Lagrangian explanation of aggregation of vortex structures of the same sign in 2D inviscid fluids. A conceptual model of zonal flow maintenance and modulation based on this idea is then developed, which produces shapes in accordance with observations.