Solar maximum, often shortened to solar max, is when the Sun’s activity, such as solar flares and coronal mass ejections, is highest in number and strength.
It is also when the number and size of sunspots on the Sun are greatest. Solar maximum occurs roughly every 11 years.
The Solar Cycle
First, we need to talk about a cycle of the Sun, which is called the solar activity or sunspot cycle. Over a roughly 11-year period, the Sun changes from a time of solar minimum to solar maximum back to solar minimum. Sometimes, this up-down cycle can last slightly longer than 11 years and sometimes slightly shortly, but on average, it is about 11 years.
At the start of the cycle, solar minimum, the Sun has very few or even no sunspots in its visible layer called the photosphere. This corresponds to the layer that provides the light we recieve from the Sun. As time progresses and the Sun starts to head toward solar maximum, we begin to see more sunspots and explosive activity such as solar flares, coronal mass ejections (CMEs), and solar energetic particles.
Solar Activity Example
Sunspot region AR3848, on October 8, 2024, released a large (X1.8) solar flare from near the center of the solar disk. This is observed in a teal image of extreme ultraviolet light as a bright flash.
It also ejected a huge (ring-shaped) cloud of solar material and magnetic field seen in a telescope that creates an artificial eclipse (a coronagraph). These explosions also created a shock wave like a sonic boom that pushed out solar particles to near the speed of light. They appear as snow on the coronagraph images, and these solar energetic particles hit the camera.
A great example of solar activity near the peak of Solar Cycle 25. Images via jhelioviewer, SDO, SOHO
Sunspots
When we reach solar maximum, the Sun has the most sunspots, and the sunspots typically grow to much bigger sizes.
They can also get more uneven and complicated than just a simple round spot. These sunspots are made of concentrations of very strong magnetic fields and are also where a lot of the explosive activity originates.
The larger and more complicated the sunspots, the more of this explosive activity and the stronger the activity. Solar maximum is not a single point or day in time but a period of roughly a year during which the average number of sunspots is at its peak.
Sunspots over time
If we look at the sunspot number over time, the up-and-down nature of the solar cycle becomes very apparent.
Image via stce.be.
The wiggly up-and-down gray line is the daily sunspot number. The red line is the monthly average, and the green line is the original prediction for the current sunspot cycle made in 2019.
We can see that the red line is far above the green prediction, meaning that the current solar cycle is larger than expected, but it also looks like the peak is coming much earlier. This means that the current solar maximum is much sooner than first expected. The red line has not definitively started going down, but we are close to or maybe even at the peak.
Solar cycles are labeled with a number.
The current solar cycle is Cycle 25, meaning there are 24 complete cycles, and the 25th is still happening.
We started counting these cycles around 400 years ago. The Sun has been around much longer than that, 4.6 billion years, and there have been solar cycles during that entire time. We only started counting sunspots regularly and consistently, starting with Cycle 1.
Image via NOAA and esa.int
If we look at several solar cycles, some solar maximums peak at a much higher sunspot number, such as Cycle 22. During this cycle and Cycles 21 and 23, solar activity was much larger than Cycle 24.
They had many more and much larger, solar flares, CMEs, and solar energetic particles. In addition to Cycle 25 appearing to peak earlier than predicted, it was also predicted to have a maximum similar to that of Cycle 24. Cycle 25 has already far surpassed this. The current solar maximum will be much larger than 24.
Looking at the most current data (as of October 2024), we can see how much Cycle 25 has surpassed Cycle 24. This graphic shows the daily sunspot number in green and the monthly average in black. It also shows the original prediction (blue) and a newer prediction that appears more accurate (red).
Image via helioforecast.space
What is the result of all this increased activity at solar maximum?
Aurora
The most obvious thing we can see is enhanced auroras, i.e., the northern and southern lights. Usually, auroras are confined near the magnetic poles, which are similar locations but somewhat different from the geographic poles. This means that auroras are usually observed at locations like Alaska, Northern Canada, Scandinavia in the northern hemisphere, and Antarctica in the southern hemisphere.
Here’s what the aurora looked in like in real-time last night over our heads in Fairbanks, Alaska pic.twitter.com/XaXDhZ5JIS
— Vincent Ledvina (@Vincent_Ledvina) October 8, 2024
Learn more about aurora here »
Impact on Technology
Many other effects from solar activity are not as obvious but can have a significant and detrimental impact on our technological society. These solar storms can impair radio communications, jeopardize electrical power systems, harm delicate satellite electronics, deteriorate satellite orbits, and induce errors in navigational devices.
Radiation from these events can potentially injure astronauts not inside Earth’s magnetosphere or atmosphere. These solar storms impact planets, moons, comets, asteroids, and even the borders of the solar system itself, affecting the entire solar system.
Thankfully, our atmosphere and the invisible magnetic field known as the magnetosphere shield our planet from the damaging impacts of radiation and plasma. The numerous spacecraft, telescopes, and scientists who monitor the radiation flow in space, or space weather, and use that data to send out Space Weather Alerts that alert people on Earth to impending radiation, further protect us.
This graphic from the European Space Agency (ESA) provides an overview of all the important parts of our technological society that are affected and often negatively impacted by the environment created by solar storms (space weather).
This graphic from the European Space Agency (ESA) provides an overview of all the important parts of our technological society that are affected and often negatively impacted by the environment created by solar storms (space weather). Image via ESA
To see what is happening daily with the Sun and space weather, visit EarthSky.org’s daily solar and space weather update.
For more on solar maximums and solar activity during this solar cycle, check out this CNN article: “The sun’s activity is peaking sooner than expected.”
