Simulating Solar Near-surface Rossby Waves by Inverse Cascade from Supergranule Energy

Abstract Rossby waves are found at several levels in the Sun, most recently its supergranule layer. We show that layer can be excited by an inverse cascade of kinetic energy from nearly horizontal motions supergranules. illustrate how this excitation occurs using a hydrodynamic shallow-water model for 3D thin rotating spherical shell. find initial small spatial scales cascades quickly to global scales, exciting whose phase velocities similar linear on sphere originally derived Haurwitz. Modest departures Haurwitz formula originate nonlinear finite amplitude effects and/or presence differential rotation. Like supergranules, small-scale our contain very little vorticity compared their divergence, but resulting almost all vortical motions. Supergranule could have mainly gone into gravity waves, we waves. Since supergranules is three or four orders magnitude larger than observed layer, there plenty available drive inverse-cascade mechanism. Tachocline previously been shown play crucial roles causing seasons space weather through interactions with flows and magnetic fields. briefly discuss various tachocline, convection zone, corona reconciled unified framework.