Meridional Circulation During the Extended Solar Minimum: Another Component of the Torsional Oscillation?

TL;DR

This study identifies a medium-high latitude meridional circulation component that precedes solar magnetic activity, offering insights into solar cycle dynamics during a prolonged minimum.

Contribution

It reveals a new meridional circulation component that develops before magnetic activity, differing from torsional oscillations in location and behavior, during an extended solar minimum.

Findings

Meridional circulation component appears at 40-50° before cycle start.

This component moves towards lower latitudes over time.

It differs from torsional oscillations in location and convergence patterns.

Abstract

We show here a component of the meridional circulation developing at medium-high latitudes (40-50 degrees) before the new solar cycle starts. Like the torsional oscillation of the zonal flows, this extra circulation seems to precede the onset of magnetic activity at the solar surface and move slowly towards lower latitudes. However, the behavior of this component differs from that of the torsional oscillation regarding location and convergence towards the equator at the end of the cycle. The observation of this component before the magnetic regions appear at the solar surface has only been possible due to the prolonged solar minimum. The results could settle the discussion as to whether the extra component of the meridional circulation around the activity belts, which has been known for some time, is or is not an effect of material motions around the active regions.