2016/04/15 by C. R. Sangeetha, S. P. Rajaguru · 1 citation
Engineering · Physics and Astronomy · #Convection #Dynamo #Fluid dynamics and aerodynamics studies #Helicity #Kinetic energy #Magnetic energy #Magnetic field #Magnetic flux #Magnetic helicity #Magnetohydrodynamics #Scientific Research and Discoveries #Solar and Space Plasma Dynamics #Vorticity #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/824/2/120
12 pages (ApJ style), 9 figures, accepted for publication in The Astrophysical Journal
arxiv created 2016/04/15 · openalex publication_date 2016/06/20 · openalex created_date 2016/06/24 · arxiv updated 2016/06/29 · openalex updated_date 2026/08/05
ABSTRACT We derive horizontal fluid motions on the solar surface over large areas covering the quiet-Sun magnetic network from local correlation tracking of convective granules imaged in continuum intensity and Doppler velocity by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory . From these we calculate the horizontal divergence, the vertical component of vorticity, and the kinetic helicity of fluid motions. We study the correlations between fluid divergence and vorticity, and between vorticity (kinetic helicity) and the magnetic field. We find that the vorticity (kinetic helicity) around small-scale fields exhibits a hemispherical pattern (in sign) similar to that followed by the magnetic helicity of large-scale active regions (containing sunspots). We identify this pattern to be a result of the Coriolis force acting on supergranular-scale flows (both the outflows and inflows), consistent with earlier studies using local helioseismology. Furthermore, we show that the magnetic fields cause transfer of vorticity from supergranular inflow regions to outflow regions, and that they tend to suppress the vortical motions around them when magnetic flux densities exceed about 300 G (from HMI). We also show that such an action of the magnetic fields leads to marked changes in the correlations between fluid divergence and vorticity. These results are speculated to be of importance to local dynamo action (if present) and to the dynamical evolution of magnetic helicity at the small-scale.