Orateur
Description
Co-authors: Lia Siegelman
Abstract: Vortex crystals are quasiregular arrays of like-signed vortices in solid-body rotation embedded within a uniform background of weaker vorticity. Vortex crystals are observed at the poles of Jupiter and in laboratory experiments with magnetized electron plasmas in axisymmetric geometries. We computationally test the hypothesis that these organized structures, with vastly different space and time scales, can be reproduced by a maximally simplified ‘quasigeostrophic’ (QG) model to two-dimensional turbulence model. The QG model shows that vortex crystals form from the free evolution of randomly excited two-dimensional turbulence on an idealized polar cap. Once formed, the crystals are long lived and survive until the end of the simulations (300 crystal-rotation periods). We identify a fundamental length scale characterizing the size of the crystal in terms of the mean-square velocity of the fluid and a parameter characterizing the variation of the Coriolis parameter close to the pole.