Solar Meridional Flow from Helioseismic Observations

Abstract:

The meridional flow in the solar interior has been studied with helioseismic techniques applied to observations from the ground-based Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO), and most recently from the Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO). The observed meridional flow is on average poleward in the near-surface layers of the Sun and its amplitude varies with the solar cycle. The meridional circulation plays an important role in dynamo theories. For example, the structure and the strength of the meridional flow might determine the duration of the solar cycle and set the timing of the reversals of the Sun’s polar fields in flux-transport dynamo models. To improve the understanding of the relationship between dynamo and meridional flow, major topics that need to be addressed are the variation of the meridional flow with the solar cycle, its variation with depth, and the meridional flow at high latitudes. I will discuss recent results from helioseismic observations.