On the penetration of meridional circulation below the solar convection zone

TL;DR

This paper investigates how large-scale meridional flows from the solar convection zone penetrate into the radiative zone, revealing that their depth depends on boundary conditions and modeling assumptions, with implications for solar magnetic processes.

Contribution

It provides a systematic analysis combining analytical and numerical models to understand the depth of meridional flow penetration below the solar convection zone.

Findings

Flow penetration depth varies with boundary conditions.

Deeper flow penetration is possible beyond traditional Ekman layer limits.

Modeling assumptions significantly influence flow behavior.

Abstract

Meridional flows with velocities of a few meters per second are observed in the uppermost regions of the solar convection zone. The amplitude and pattern of the flows deeper in the solar interior, in particular near the top of the radiative region, are of crucial importance to a wide range of solar magnetohydrodynamical processes. In this paper, we provide a systematic study of the penetration of large-scale meridional flows from the convection zone into the radiative zone. In particular, we study the effects of the assumed boundary conditions applied at the convective-radiative interface on the deeper flows. Using simplified analytical models in conjunction with more complete numerical methods, we show that penetration of the convectively-driven meridional flows into the deeper interior is not necessarily limited to a shallow Ekman depth but can penetrate much deeper, depending on how the convective-radiative interface flows are modeled.