Solar Media Circulation System

What is solar meridional circulation?

Solar meridional circulation is an axisymmetric flow system, extending from the equator to the poles (\ (\sim \) 20 m/s at the surface, \ (\approx \) 1% of the mean solar rotation rate), plunging inwards and subsequently completing the circuit in the interior through an equatorward return flow and a radially outward flow back up to the surface.

Why is MC important in a solar cycle?

In recent decades, the timescale associated with the transport of magnetic flux by MC has been identified as crucial to the solar-cycle period. In particular, the flow speed and direction in the deep-interior layers is extremely important to the overall behaviour of solar magnetism.

Why is solar rotation more important than MC?

Because rotation is of a much higher magnitude than MC, errors in the determination the solar rotation axis (Beck and Giles 2005) can cause rotation to add to the weak MC signals. Thus, it is important that the observed image is not rotated in the plane of the camera with respect to the rotation axis.

Why do MC signals vary if the Sun rotates?

These systematic shifts, although small, are due to a slight rotation of the observed image with respect to the true rotation axis of the Sun (\ (0.2^\circ \) in the case of MDI), thereby causing solar rotation to contribute to MC signals. This can lead to notable errors in inferring MC because of the large magnitudes of rotation speeds.