Why is there a pecular little black spot on the sun today?
This answer will surprise you:
every 11 years, the sun’s magnetic field flips. And it all starts with a show of black sunspots on its surface.
The sun is a complex ball of many magnetic fields, but it is essentially one big magnet with well-defined north and south poles.
We know the sun gives us light. And we all know that we should avoid looking directly at it. And we know we can’t go there, as with all planets, moons and asteroids. So, why do scientists study it? What do we need to know about the sun?
There’s a bunch of reasons for studying the sun.
First, from a practical point of view, we cannot go to the sun, but material from the sun can come to us. It comes to the Earth in pretty ways to create the northern lights (aurora borealis), and it fills our body with necessary vitamin D.
But the same processes also produce storms which expand the sun’s outer atmosphere and that produces drag on satellites. Those storms also produce high-energy particles, which have an effect on people in space [astronauts]. And if we have a large storm, it can damage electrical infrastructure on the ground.
Are the northern lights directly linked to the increased activity of the sun? Yes, and experts expect the number of aurora to increase in the next few years, as the solar activity increases. That’s one of the ways we understand the solar cycle.
The Solar Cycle 25 Prediction Panel has been detecting increased sun activity for at least six months now. This increased activity is part of an 11-year-cycle, and we understand the sun is now beyond its so-called “minimum.”
What is that minimum and what are the signs of increased activity?
The sun is currently entering its 25th numbered cycle. We began observing its cycles systematically before we started numbering them, so it’s been over 300 years.
The main difference between the minimum and the maximum in a solar cycle is the number of sunspots we see on the surface. And if you count the number of sunspots, you find they go from a very low number — the minimum, which we’ve just passed — up to a maximum, where there are many sunspots on the surface at any one time, and then it decreases again.
And what exactly are sunspots?
The surface of the sun is very bright. It’s about 5,780 degrees Kelvin (5,500 degrees Celsius or 10,000 degrees Fahrenheit). But occasionally we get these dark patches, which are a couple of thousand degrees cooler. They appear when energy from deep inside the sun is being blocked or prevented from reaching the surface. It’s being blocked by a strong magnetic field. So, a sunspot is where a magnetic field gets so strong that it stops energy from inside the sun escaping to the surface.
Are there other signs of increased activity?
There are small bright features called faculae, which appear as activity increases. Faculae are also magnetic, but because they are small — about four hundred kilometers (248 miles) across — they are not as spectacular as sunspots. But there are a lot of these bright points during times of high activity, and that makes the sun a little brighter when it’s more active, than during periods of low activity, such as now.
When the increased activity simmers down again, will he spots disappear?
The spots only last a short time, from days to a few weeks. But what’s interesting is where they come from. As with the Earth, the sun is rotating. One rotation of the sun takes about 27 days.
Now, at the beginning of a cycle, such as now, at the minimum, we have a simple magnetic field, which goes through the sun, entering from one pole and coming out the other, like a line or a piece of string.
The Sun is not a solid object. It is giant ball of gas and plasma. Some parts of the Sun rotate more slowly than other parts. At the equator, the Sun spins pretty fast. It takes 25 days to turn all the way around. It turns more slowly at the poles. The poles take 34 days to spin around once.
But as the equator rotates faster than the poles, the magnetic field gets wound up — a bit like winding up a clock spring, and after four or five years the sun’s magnetic fields* become overwound and unstable. An overwound magnetic field will want to break out of the sun and in doing that, it forms sunspots.
The sunspots then break up into smaller elements and they go to the poles. That’s part of a process that eventually reverses the direction of the sun’s magnetic field, its polarity. So, if it was initially north-south, 11 years later it will be south-north. And the whole process repeats itself in every 11-year-cycle.
This is why you’ll sometimes hear astronomers refer to the solar cycle, solar maxima and minima and the sunspot cycle.
What is our current solar cycle?
Currently the sun is in its 25th solar cycle. It is thought to have started with solar minimum in December 2019, and expected to peak with 115 sunspots in July 2025.
If sunspots are active, more solar flares will result creating an increase in geomagnetic storm activity for Earth. Therefore during sunspot maximums, the Earth will see an increase in the Northern and Southern Lights and a possible disruption in radio transmissions and power grids. Then the field reverses and resets, the sunspots disappear and the Sun becomes relatively calm again.
This means summer 2025 could bring us some more power outages and cellphone signal disruptions. Luckily we have a few year to prepare…