Other than the North and South Poles, have you seen or heard of breathtaking auroras appearing in the skies? These auroras are a result of geomagnetic storms, caused by coronal mass ejections from the Sun. What other weird and wonderful phenomena happens in the Sun, and how does the solar cycle come into play?
What is the solar cycle?
The solar cycle is an approximately 11-year long cycle of solar activity, though its duration can range from 8 to 14 years. It is indicated by the frequency and intensity of sunspots, and is driven by the Sun’s magnetic field. Every cycle, the Sun’s magnetic field flips, with the north pole becoming the south pole, and vice versa. This change in the magnetic field results in solar phenomena like sunspots and coronal mass ejections.
Sunspots
Sunspots are cooler and darker patches on the Sun’s surface. Their appearance varies with the solar cycle, with the most sunspots appearing during solar maximum, when solar activity is the highest.
Sunspots also appear in different positions throughout the cycle. During solar maximum, they gather around latitudes of 30 degrees north and south, and move towards the equator during solar minimum.
Solar flares
Solar flares are large explosions of electromagnetic radiation from the surface of the Sun. They happen when magnetic energy built up from the Sun’s atmosphere is suddenly released.
Like sunspots, they are intrinsically linked to the solar cycle. They tend to occur in regions where sunspots appear, making the number of sunspots in a region a good predictor of the likelihood of solar flares.
Solar flares have different classifications depending on their intensity, namely the X-, M-, C-, B-, and A-class flares, in decreasing order of intensity. X-class and M-class flares are very strong, which can trigger coronal mass ejections and cause significant disruptions to radio communication on Earth.
Solar Wind
Solar wind is a continuous stream of protons and electrons from the Sun’s corona, or outer atmosphere. These particles travel at speeds ranging from 400 to 800 kilometers per second.
When the solar wind reaches Earth, the particles travel along Earth’s magnetic field lines towards the poles, where they interact with the atmosphere to form auroras, such as the Aurora Borealis and Aurora Australis.
Coronal Mass Ejections (CME)
Like solar wind, coronal mass ejections are expulsions from the Sun’s corona, but this time, they are a much larger ejection of plasma and magnetic field. They can travel at up to 3000 kilometers per second.
CMEs can cause geomagnetic storms, which are major disturbances in Earth’s magnetosphere. These storms can heat up the upper atmosphere, causing its density to increase and creating extra drag for satellites. This heat can also cause errors in GPS positioning information and disrupt navigation systems like the Global Navigation Satellite System (GNSS).
Though CMEs can be disruptive, they also bring astonishing sights to our skies. The resultant geomagnetic storms can bring auroras to people who don’t live on the North or South Poles due to a similar effect solar wind has in the Poles.
Conclusion
The Sun is a formidable force, and its phenomena, while creating beautiful lights in the sky on Earth, can also cause great disruptions to our communication and navigation systems. That is why scientists closely monitor solar activity and the solar cycle to prepare for such disruptions caused by solar phenomena.
Works Cited
Dobrijevic, D. (2022). Solar cycle: What is it and why does it matter? [online] Space.com. Available at: https://www.space.com/solar-cycle-frequency-prediction-facts [Accessed 31 Mar. 2024].
Dobrijevic, D. (2022). Solar flares: What are they and how do they affect Earth? [online] Space.com. Available at: https://www.space.com/solar-flares-effects-classification-formation [Accessed 31 Mar. 2024].
NASA (2017). Sunspots and Solar Flares :: NASA Space Place. [online] Nasa.gov. Available at: https://spaceplace.nasa.gov/solar-activity/en/ [Accessed 31 Mar. 2024].
National Oceanic and Atmospheric Administration (2019). Coronal Mass Ejections | NOAA / NWS Space Weather Prediction Center. [online] Noaa.gov. Available at: https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections.
National Oceanic and Atmospheric Administration (n.d.). Geomagnetic Storms | NOAA / NWS Space Weather Prediction Center. [online] Noaa.gov. Available at: https://www.swpc.noaa.gov/phenomena/geomagnetic-storms [Accessed 31 Mar. 2024].
Nola Taylor Redd (2018). What is Solar Wind? [online] Space.com. Available at: https://www.space.com/22215-solar-wind.html [Accessed 31 Mar. 2024].
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