Search

Solar activity, such as sunspots and flares, has a great impact on humans, living beings, and technologies in the whole world. Changes in sunspots will influence high-frequency and space-navigation radio communications. Based on the full-disk, southern and northern hemispheres sunspot areas (SAs) data in 1874–2023 from the Royal Observatory, Greenwich (RGO) USAF/NOAA, extreme value theory (EVT) is applied to predict the trend of the 25th and 26th solar cycles (SCs) in this work. Two methods with EVT, the block maxima (BM) approach and the peaks-over-threshold (POT) approach, are employed to research solar extreme events. The former method focuses on each block's maximum sunspot areas value and is applied for the generalized extreme value (GEV) distribution. The latter method aims to select the extreme values exceeding a threshold value and is used to obtain the generalized Pareto (GP) distribution. It is the first time that the EVT is applied on the sunspot areas data from the Royal Observatory, Greenwich (RGO) USAF/NOAA. The analysis indicates that the estimated 8-year return levels for sunspot areas are 5701 and 6258 using the two methods, while the estimated 19-year return levels are all 7165. This suggests that the trends of the 25th and 26th solar cycles will be stronger than that of the 24th solar cycle. [ABSTRACT FROM AUTHOR]

It is necessary to better understand the dynamic process of solar differential rotation. Here the hand-drawing sunspot group records from 1958 to 2015 of Yunnan Observatories (YNAO) are used to study the solar rotation profile. Firstly, the rotation profile in each solar cycle 19-23 is calculated. Secondly, the rotation parameters (equatorial rotation velocity A and differential gradient B) of YNAO are compared with the well-known earlier results. Finally, the rotation parameters in the northern and southern hemispheres during each solar cycle 19-23 are summarized. The main conclusions we reached are as follows: (1) The average difference of the equatorial rotation velocity and differential gradient, between YNAO sunspot and other sunspot datasets, are 0.09 and 0.4, respectively. (2) The magnitudes of the gradient B in the northern hemisphere are larger than that in the southern hemisphere at even-number cycles, and it will approximately reverse at odd-number cycles. [ABSTRACT FROM AUTHOR]

Studying solar filaments can help in understanding the distribution of large-scale field in the solar atmosphere and provide useful insights into the nature of the solar magnetic field. Recently, the National Astronomical Observatory of the Chinese Academy of Sciences has collected huge volumes of data about solar filaments from several international observing stations for nearly 100 years. Designing a database, as well as establishing a networked tool for making the best of it, are necessary to provide efficient and convenient access to the data for researchers. In this study, we introduce a solar filament database, involving digital image data of nearly 45 terabytes, based on MySQL and a data management platform named database management system of hundred years of solar filament archives (http://faste.ctgu.edu.cn) that adopts Browser/Server mode and is written in the Java programming language. From this data system, users can realise multi-property query on the basis of demands, download data under multiple conditions, perform visual query for information on one single filament, view long-term data statistics of filament properties, and implement extensions and management of the database. [ABSTRACT FROM AUTHOR]