Hydrodynamic Properties of the Sun’s Giant Cellular Flows

Measurements of the large cellular flows on Sun were made by local correlation tracking supergranules seen in full-disk Doppler images obtained HMI instrument NASA SDO satellite. The hourly measurements averaged over 34 days to produce daily maps latitudinal and longitudinal velocities. While at all latitudes are largely form vortices with left-handed helicity north right-handed south, there key distinctions between low latitude high cells. cells have roughly circular shapes, lifetimes about one month, rotate nearly rigidly, do not drift latitude, exhibit any flow. long extensions that spiral inward toward poles. They several months, differentially poleward speeds approaching 2 m s$^{-1}$, a strong prograde equatorward flows. Spherical harmonic spectral analyses confirm dominated curl component RMS velocities 12 s$^{-1}$ wavenumber $\ell$ = 10. Fourier transforms time indicate two notable components - an $m \pm\ell$ feature representing \pm1$ component. dispersion relation for is well represented derived Rossby waves. has constant temporal frequency indicating features advected differential rotation rates representative base convection zone latitudes. motions these further suggest meridional flow equatorward.