Related papers: A Statistical Analysis of Sunspot Active Longitude…
A striking feature of the solar cycle is that at the beginning, sunspots appear around mid-latitudes, and over time the latitudes of emergences migrate towards the equator. The maximum level of activity varies from cycle to cycle. For…
Analysis of the structure and dynamics of the magnetic field of the Sun is fundamental for understanding of the origin of solar activity and variability as well as for the study of solar-terrestrial relations. Observations of the large…
During the emergence of sunspot groups the footpoints of their leading and following parts move apart. This diverging motion results in the stretching of the active regions, which continues during the decay phase. The aim of the present…
Understanding coronal structure and dynamics can be facilitated by analyzing green-line emission, which enables the investigation of diverse coronal structures such as coronal loops, streamers, coronal holes, and various eruptions in the…
Tilt angles of close to 30,600 sunspots are determined using Mount Wilson daily averaged magnetograms taken from 1974 to 2012, and MDI/SoHO magnetograms taken from 1996 to 2010. Within a cycle, more than 90% of sunspots have a normal…
Long-term modulation of solar differential rotation was studied with data from Mt. Wilson and our original observations during Solar Cycles 16 through 23. The results are: i) The global B-value (i.e. latitudinal gradient of differential…
Digitized images of full disk CaK spectroheliograms from two solar observatories were used to study cycle variation of ephemeral regions (ERs) over ten solar cycles 14-23. We calculate monthly averaged unsigned latitude of ERs and compare…
The activity-related variations in the solar acoustic frequencies have been known for 30 years. However, the importance of the different contributions is still not well established. With this in mind, we developed an empirical model to…
We investigate solar activity by focusing on double maxima in solar cycles and try to estimate the shape of the current solar cycle (Cycle 24) during its maximum. We analyzed data for Solar Cycle 24 by using Learmonth Solar Observatory…
It has been known that some solar activity indicators show a double-peak feature in their evolution through a solar cycle, which is not conspicuous in sunspot number. In this letter, we investigate the high solar dynamic activity in the…
An analysis of the tilt angles of the active regions in 15-24 activity cycles was performed. We used data from measurements of magnetic fields in the sunspot umbra in the period 1918 -2019 at the Mount Wilson Observatory, as well as the…
The level of solar magnetic activity, as exemplified by the number of sunspots and by energetic events in the corona, varies on a wide range of time scales. Most prominent is the 11-year solar cycle, which is significantly modulated on…
The frequencies of the solar acoustic oscillations vary over the activity cycle. The variations in other activity proxies are found to be well correlated with the variations in the acoustic frequencies. However, each proxy has a slightly…
We study the visibility of sunspots and its influence on observed values of sunspot region parameters. We use Virtual Observatory tools provided by AstroGrid to analyse a sample of 6862 sunspot regions. By studying the distributions of…
We present a systematic study of sunspot physical parameters using full disk magnetograms from MDI/SoHO and HMI/SDO. Our aim is to use uniform datasets and analysis procedures to characterize the sunspots, paying particular attention to the…
Solar activity is an important driver of long-term climate trends and must be accounted for in climate models. Unfortunately, direct measurements of this quantity over long periods do not exist. The only observation related to solar…
Through meticulous daily observation of the Sun's large-scale magnetic field the Wilcox Solar Observatory (WSO) has catalogued two magnetic (Hale) cycles of solar activity. Those two (~22-year long) Hale cycles have yielded four…
The hemispheric asymmetry of sunspot activity observed possesses a regular component varying on a time scale of several solar cycles whose origin and properties are currently debated. This paper addresses the question of whether the…
In a recent work, Kilcik et al. (2017), have detected the temporal and periodic behavior of sunspot counts (SSC) in flaring (i.e. C, M, or X class flares), and non-flaring active regions for the last two solar cycles, covering the period:…
A long-term variation is detected in the north-south differences of the solar activity, the phase difference of hemispheric cycles alternates by four Schwabe cycles. This variability is demonstrated by two different methods. It can be the…