THE SOLAR CYCLE

Hi, I’m Marley, the astronomer here at the Space Centre. Since we are well into summertime, I thought we could take the month to take a closer look at our star, the Sun, which is currently giving scientists some surprises during this current solar cycle.

Our Sun goes through periods of activity on a roughly 11 year cycle from solar minimum to solar minimum (or solar maximum to solar maximum). During this cycle, the Sun varies between minimum and maximum periods of activity. The number, and size, of sunspots and solar flares changes, along with the amounts of solar radiation and ejected solar material coming from the surface. Additionally, when the Sun reaches solar maximum, the magnetic field flips!

Scientists track solar activity by counting the sunspots seen on the Sun’s surface. This is not a new technique: human beings have been observing sunspots for thousands of years! Periods of lower activity will have fewer sunspots, and periods of higher activity will have more. In December 2019, the sunspot average for the past year dropped to 1.8. After that, it began to increase, indicating that we had passed through the solar minimum, and had started a new cycle: solar cycle 25. The solar maximum for this solar cycle should occur in 2025. What can we expect to see, and are there any risks?

Back in December of 2019, the Solar Cycle 25 Prediction Panel predicted that solar cycle 25 was going to be pretty quiet, with the maximum average number of sunspots reaching 115 at around July 2025. However, the Sun has already exceeded predictions in the first three years! If you live in the lower mainland, you may have noticed a lot of opportunities to see the northern lights. There have also been quite a few strong solar flares. These two events are related. The aurora are caused by energized particles from the Sun interacting with the Earth’s magnetic field and upper atmosphere. The magnetic field funnels these particles towards the poles, which is why they are typically seen at very northern and southern latitudes. But when the Sun is particularly active, there are more opportunities for the aurora to happen, and the events causing them, like solar flares, may be stronger. As we approach solar maximum, there will probably be more activity like we have been seeing.

As said before, this increase in activity can produce the beautiful aurora at lower latitudes, but it can also pose a serious risk to the space environment. In February 2022, SpaceX lost around 40 Starlink satellites due to the effects on Earth’s atmosphere during a geomagnetic storm. The storm was caused by a coronal mass ejection – a mass of plasma from the Sun – that ended up hitting Earth and interacting with the magnetosphere and atmosphere. The part of our atmosphere called the thermosphere warmed up, and increased in density. This increases atmospheric drag, which slows down anything moving through the atmosphere. As a result, the Starlink satellites experienced more atmospheric drag than expected, causing them to deorbit and burn up. These clouds of plasma can also cause radio blackouts, and can pose a risk to our astronauts on the International Space Station.

A question that often follows is ‘Could the solar cycle influence climate change on Earth?’ In short, the answer is no. While the differences in these periods of activity sound extreme, the total radiation from the Sun only changes by 0.15%! This is less than what is necessary for the solar cycle to be the main contributor to climate change. Additionally, scientists have not found any compelling evidence of this 11 year cycle replicated anywhere on Earth, aside from our upper atmosphere. We would expect to see changes in surface temperature, rainfall, even wind patterns! You can read more about the solar cycle and climate change here.

This current solar cycle has already given us our fair share of excitement, and it will be interesting to see what the Sun throws our way as we approach solar maximum. Until then, check out some Sun related activities and science missions below!