Research On The Sun's Differential Rotation Based On Hand-drawing Sunspot Data From Yunnan Observatory

The differential rotation of the sun has always been an important issue in solar physics.It plays an important role in the conversion of the polar and toroidal magnetic fields of the sun and is an important basis for explaining the empirical model of the origin of solar activity and the theory of solar dynamo.Among them,using sunspots as tracers to calculate the rotation rate of the sun is a common method in the subject.The hand-drawing sunspot data of the Yunnan Observatory of the Chinese Academy of Sciences(hereinafter referred to as Yuntai)has accumulated more than 20,000 observation records,and the time span is nearly 60 years.It has a time zone advantage in the problem of differential rotation of the sun,which makes the hand-drawing sunspots of Yuntai record is scarce in the subject of differential rotation of the sun.Before using this data set for research,it is necessary to verify the accuracy of the sunspot position and area information in this data set,as well as a comparison experiment with the differential rotation results of the predecessors.This article is divided into the following five parts:Chapter 1 Overview.It includes the layered structure of the sun,the main activities of the sun,and a brief introduction to the sun's differential rotation.Make a basic outline for the following content.In the second chapter,we selected 268 records of hand-drawing sunspot records of Yunnan Observatory,calculated their position and area information through image processing technology,and conducted error analysis.The two sets of data results adopt the method of mutual correction,calculate the correction coefficient,and perform error statistics.We found that the accuracy of the sunspot latitude is 0.127 degrees and the accuracy of the sunspot longitude is 2.29 degrees.The area information of hand-drawing sunspots is systematically smaller than that of satellite images,with an accuracy of 16.36?Hem.Chapter 3 gives an introduction to the calculation method of solar rotation.First introduced how to calculate the solar rotation rate at a certain latitude in a fixed time period.Then,the calculation process of calculating all the sun rotation sample points and the method of eliminating abnormal data are given.Finally,the process of fitting the data to the model is given.Chapter 4 compares the solar rotation results based on sunspot databases of other observatories.First,we carefully analyzed the criteria,time period,and fitting formula for screening sunspot records.Next,the solar rotation rate result corresponding to the YNAO data is calculated by replacing the original data and keeping the calculation method unchanged.Finally,the results are compared to draw a conclusion.We conclude that the average absolute error of the rotation speed of the equator is 0.075,and the absolute error of the average rotation gradient is 0.34.In addition,the data are also used to calculate the rotation contour of each solar activity cycle,a comparative study of the asymmetry of the rotation of the northern and southern hemispheres,and the characteristics of the solar rotation with time.Chapter 5 briefly summarizes the main contents of this article.And made further prospects for the work to be carried out in the future.