Forward Modeling Helioseismic Signatures of One- and Two-cell Meridional Circulation

Abstract

Using a 3D global solver of the linearized Euler equations, we model acoustic oscillations over background velocity flow fields of single-cell meridional circulation with deep and shallow return flows as well as a double-cell meridional circulation profile. The velocities are generated using a mean-field hydrodynamic and dynamo model -moving through the regimes with minimal parameter changes; counter-rotation near the base of the tachocline is induced by sign inversion of the non-diffusive action of turbulent Reynolds stresses (Λ-effect) due to the radial inhomogeneity of the Coriolis number. By mimicking the stochastic excitation of resonant modes in the convective interior, we simulate realization noise present in solar observations. Using deep-focusing to analyze differences in travel-time signatures between the three regimes, as well as comparing to solar observations, we show that current helioseismology techniques may offer important insights about the location of the return flow, however, that it may not be possible to definitively distinguish between profiles of single-cell or double-cell meridional circulation.

Solar large-scale magnetic field and cycle patterns in solar dynamo

“…Howe et al 2011). The parameters of meridional circulation are debatable (see, e.g, the recent discussion in Gizon et al 2020 andStejko et al 2021 andreferences therein). Our knowledge of the turbulent dynamo effects is even more uncertain Brandenburg (2018).…”