# Changes in the solar rotation over two solar cycles

## TL;DR

This study analyzes how solar rotation has evolved over two solar cycles using helioseismic data, revealing cycle-dependent differences in rotation patterns, zonal flows, and tachocline properties.

## Contribution

It provides a detailed comparison of solar rotation changes between Cycles 23 and 24, highlighting differences in zonal flows and tachocline characteristics.

## Key findings

- Zonal flows are weaker in Cycle 24 than in Cycle 23.
- Significant temporal variation in rotation rate across the tachocline.
- Emergence signs of Solar Cycle 25 observed in zonal flow patterns.

## Abstract

We use helioseismic data from ground and space-based instruments to analyze how solar rotation has changed since the beginning of solar Cycle 23 with emphasis on studying the differences between Cycles 23 and 24. We find that the nature of solar rotation is indeed different for the two cycles. While the changes in the latitudinally independent component follows solar-cycle indices, some of the other components have a more complicated behavior. There is a substantial change in the behavior of the solar zonal flows and their spatial gradients too. While the zonal flows are in general weaker in Cycle 24 than those in Cycle 23, there are clear signs of the emergence of Cycle 25. We have also investigated the properties of the solar tachocline, in particular, its position, width, and the change (or jump) in the rotation rate across it. We find significant temporal variation in the change of the rotation rate across the tachocline. We also find that the changes in solar Cycle 24 were very different from those of Cycle 23. We do not find any statistically significant change in the position or the width of the tachocline.