1998/09/24 by Sarbani Basu, H. M. Antia, S. C. Tripathy · 4 citations
Computer Science · Physics and Astronomy · #Amplitude #Atmospheric sciences #Computational physics #Convection #Convection zone #Equator #Geodesy #Geology #Geometry #Geophysics #Helioseismology #Latitude #Magnetic field #Mechanics #Meridional flow #Optics #Oscillation (cell signaling) #Physics #Solar Radiation and Photovoltaics #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #Zonal and meridional #Zonal flow (plasma) #astro-ph
paper · pdf · doi:10.1086/306765
published as Astrophys.J. 512 (1999) 458 · aastex, 12 figures, to appear in Ap.J
arxiv created 1998/09/24 · openalex publication_date 1999/02/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Ring diagram analysis of solar oscillation power spectra obtained from Michelson Doppler Imager data is carried out to study the velocity fields in the outer part of the solar convection zone. The three-dimensional power spectra are fitted to a model that has a Lorentzian profile in frequency and includes the advection of the wave front by horizontal flows in order to obtain the two components of the subsurface flows as a function of the horizontal wave number and radial order of the oscillation modes. This information is then inverted using the optimally localized averages method and regularized least squares method to infer the variation in horizontal flow velocity with depth. The average rotation velocity at different latitudes obtained by this technique agrees reasonably with helioseismic estimates made using frequency-splitting data. The shear layer just below the solar surface appears to consist of two parts, with the outer part measuring up to a depth of 4 Mm where the velocity gradient does not show any reversal up to a latitude of 60°. In the deeper part the velocity gradient shows reversal in sign around a latitude of 55°. The zonal flow velocities inferred in the outermost layers appear to be similar to those obtained by other measurements. A meridional flow from equator poleward is found. It has a maximum amplitude of about 30 m s -1 near the surface, and the amplitude is nearly constant in the outer shear layer.