Dust Devil Dynamics

The theory and simulation tools of fusion plasma physics are used to describe the dynamics of dust devils. The Grad-Shafranov equation governs the poloidal flow stream function and gives a class of solutions for steady axisymmetric flows. The high core velocity is limited by viscous dissipation with a modified Burger's vortex model. Since the Reynolds number is not large, these structures are well represented on vector computers in contrast to collisionless plasmas. Electrically charged sand grains ($10-100 \mu m$) are integrated as passively convected by the winds and results in vertical electric fields that assist the vortices in lifting materials off the ground and into the vortex. The rotating charged dust produces a magnetic field. Thus, some of the important properties of high temperature plasmas are manifested in these common, small scale coherent structures.