2010/08/25 by David H. Hathaway, Peter E. Williams, Kevin Dela Rosa +1
Physics and Astronomy · #Advection #Astro and Planetary Science #Differential rotation #Doppler effect #Meridional flow #Rotation (mathematics) #Rotational symmetry #Solar and Space Plasma Dynamics #Solar rotation #Stellar, planetary, and galactic studies #Zonal and meridional #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/725/1/1082
15 pages, 8 figures
arxiv created 2010/08/25 · openalex publication_date 2010/11/23 · arxiv updated 2015/05/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We show that the motions of supergranules are consistent with a model in which they are simply advected by the axisymmetric flows in the Sun's surface shear layer. We produce a 10 day series of simulated Doppler images at a 15 minute cadence that reproduces most spatial and temporal characteristics seen in the SOHO /MDI Doppler data. Our simulated data have a spectrum of cellular flows with just two components—a granule component that peaks at spherical wavenumbers of about 4000 and a supergranule component that peaks at wavenumbers of about 110. We include the advection of these cellular components by the axisymmetric flows—differential rotation and meridional flow—whose variations with latitude and depth (wavenumber) are consistent with observations. We mimic the evolution of the cellular pattern by introducing random variations to the phases of the spectral components at rates that reproduce the levels of cross-correlation as functions of time and latitude. Our simulated data do not include any wave-like characteristics for the supergranules yet can reproduce the rotation characteristics previously attributed to wave-like behavior. We find rotation rates which appear faster than the actual rotation rates and attribute this to projection effects. We find that the measured meridional flow does accurately represent the actual flow and that the observations indicate poleward flow to 65°–70° latitude with equatorward countercells in the polar regions.