Differential rotation measurement of soft X-Ray corona

TL;DR

This study measures the latitudinal variation of solar rotation in the soft X-ray corona over a decade, revealing its dependence on solar activity cycle and comparing it with the photosphere and chromosphere.

Contribution

It provides detailed measurements of coronal differential rotation using SXT data, highlighting its variation over solar cycles and its relation to other solar layers.

Findings

Coronal equatorial rotation rate is similar to that of the photosphere.

Differential rotation varies with latitude and solar activity cycle.

Coronal rotation period correlates with sunspot numbers.

Abstract

The aim of this paper is to study the latitudinal variation in the solar rotation in soft X-ray corona. The time series bins are formed on different latitude regions of the solar full disk (SFD) images that extend from 80 degree South to 80 degree North. These SFD images are obtained with the soft X-ray telescope (SXT) on board the Yohkoh solar observatory. The autocorrelation analyses are performed with the time series that track the SXR flux modulations in the solar corona. Then for each year, extending from 1992 to 2001, we obtain the coronal sidereal rotation rate as a function of the latitude. The present analysis from SXR radiation reveals that; (i) the equatorial rotation rate of the corona is comparable to the rotation rate of the photosphere and the chromosphere, (ii) the differential profile with respect to the latitude varies throughout the period of the study; it is more in the year 1999 and least in 1994 and (iii) the equatorial rotation period varies systematically with sunspot numbers and indicates its dependence on the phases of the solar activity cycle.