Lunt H-alpha telescope
(Click on picture for a larger image)
Recently (Jun 28), I set up my Lunt solar-observations-only telescope (above - it contains the proper Hydrogen-alpha light filters to cut the sunlight to the correct, safe level). I was hoping to see some activity. In the last couple of years there has been very little of that. We may just have gone through a minimum of the eleven year sun cycle. The state of the solar cycle is determined by solar observatories world-wide, counting the number of sun spots over the years.
Looking through my solar telescope, the sun did show a number of prominences which had also been absent for a lengthy period. I did not see any sunspots, though. There were a few dark streaks; these are prominences which we see "from above". They are just like the ones we see at the sun's edge, but they originate on the surface away from the edge. They look darker because, as they move away from the surface, they cool down and therefore emit a little less light. This is obvious when looking at prominences at the edge of the sun, which are also fainter than the sun's surface. Here is a picture I took of the sun some years ago; it is similar to what I saw on Jun 28.
The Sun in H-alpha light
(Click on picture for a larger image)
The diameter of the sun is 104 times that of earth. If you mentally string 104 earths across the sun and compare the size of the prominences in the picture, it becomes obvious that the prominences easily exceed the size of the earth. The hydrogen gas and plasma of which the prominences are composed follow magnetic lines of force. Magnetism and its constant changes are a major part of the sun's activity. I think of the sun as a magnetized cauldron. Solar material is constantly being stirred and ejected and, if the force of the ejections are strong enough, this material will disperse into space. The earth is often in the path of such material; northern and southern lights are one effect. There are also interferences with wireless communications and power grids. Astronauts in space have to be protected as much as possible from this powerful radiation.
I think that we are finally entering the next solar cycle. The cycle should actually have a 22 year length. When sunspots appear as a pair, for instance, the leading spot (in the direction of the sun's rotation) could be magnetic north polarity. The following spot in the pair then has the south polarity. After the next minimum occurs, sunspots in the next eleven year period reverse their paired relationship polarity (south leading, north following). Nobody has a good explanation for the cause this characteristic. The next eleven-year period after the preceding two then exhibits sunspot pairs with leading north and following south polarities again. Many other solar phenomena, such as solar flares, coronal loops, solar radiation, etc. are all synchronized in some way with these magnetic changes. There are many reasonable theories, but we have limited factual knowledge about what happens inside the sun. The eleven-year cycle has been observed for many centuries (the last 400 years are quite well documented).
Over the last 10 years, NASA's Solar Dynamics Observatory, in a geostationary orbit around earth, has collected around 425 million gigabytes of data (one image every three quarters of a second, according to NASA). This effort has contributed much to an increased knowledge of how the sun interacts with earth, and the solar system.
Here is an excerpt from Wikipedia:
Solar cycle
The solar cycle or solar magnetic activity cycle is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the solar surface. Sunspots have been observed since the early 17th century and the sunspot time series is the longest, continuously observed time series of any natural phenomenon. Accompanying the 11 year quasi-periodicity in sunspots, the large-scale dipolar magnetic field component of the Sun also flips every 11 years, however, the peak in the dipolar field lags the peak in the sunspot number, with the former occurring at the minimum between two cycles. Levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation, from active to quiet to active again, with a period of 11 years. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as auroras.Wikipedia
If you have appropriate equipment - proper solar filters for your general-purpose telescopes - or if you follow the rules of projecting the sun onto a screen, you may want to check for the visible state of sunspots over the next years. WARNING: Never look at the sun directly without correct filters through telescopes, binoculars, or even the naked eye. Damage to the eye, possibly including blindness, can be a result, either instantly or as vision problems later in life.
Solar observations and photography are a great way to do astronomy - you can have your regular sleep hours; no need to stay awake for much of the night. There is much information about the sun (and its effects on the earth) in the RASC's Observer's Handbook (starting on page 184 of the 2020 edition). Try it, you might like it.
