Characteristics of solar wind rotation

TL;DR

This study analyzes 54 years of solar wind data to reveal that high-velocity solar wind rotates faster and exhibits different velocity-rotation relationships compared to low-velocity wind, with rotation rates linked to solar activity cycles.

Contribution

It provides new insights into the velocity-dependent rotation characteristics of solar wind and their correlation with solar activity over multiple decades.

Findings

High-velocity solar wind rotates faster than low-velocity wind.

Rotation rate increases with velocity for high-velocity wind, decreases for low-velocity wind.

Yearly rotation rate negatively correlates with sunspot number with a 3-year lead.

Abstract

Over 54 years of hourly mean value of solar wind velocity from 27 Nov. 1963 to 31 Dec. 2017 are used to investigate characteristics of the rotation period of solar wind through auto-correlation analysis. Solar wind of high velocity is found to rotate faster than low-velocity wind, while its rotation rate increases with velocity increasing, but in contrast for solar wind of low velocity, its rotation rate decreases with velocity increasing. Our analysis shows that solar wind of a higher velocity statistically possesses a faster rotation rate for the entire solar wind. The yearly rotation rate of solar wind velocity does not follow the Schwable cycle, but it is significantly negatively correlated to yearly sunspot number when it leads by 3 years. Physical explanations are proposed to these findings.