While to us the Sun may appear reliable and consistent, it actually is a very volatile object. The Sun is a giant ball of gas and plasma fueled by nuclear fission. On its surface there are electrically charged gases the generate strong magnetic fields. These gases are constantly moving, which causes the magnetic fields to get manipulated, stretched, and intertwined. All of this motion causes a lot of activity on the Sun’s surface, called solar activity.
Table of Contents
The Solar Cycle
Sometimes the Sun’s surface is calmer than at other times. The amount of activity changes with the stages of the solar cycle. The solar cycle is the cycle of the Sun’s magnetic field. Approximately every 11 years the Sun’s magnetic field flips. This means its north and south poles switch places. 11 more years and they flip back. This solar cycle affects all the activity on the Sun’s surface. As these magnetic fields change so does the solar activity. Below is a map of the Sun’s magnetic fields as created by a computer model.
Image Credit: NASA/SDO/AIA/LMSAL
One way to track the solar cycle is to count the number of sunspots on the surface of the Sun. Sunspots are dark areas on the surface of the Sun. The Sun is said to be at a solar minimum when it has the least number of sunspots, this occurs at the beginning of a solar cycle. The middle of the solar cycle is a solar maximum when we see the most sunspots on the Sun’s surface. As the cycle continues it fades back into a solar minimum. Below we can see the evolution of the Sun from a solar minimum to a solar maximum and back again over a 10-year span.
Image Credit: Dan Seaton/European Space Agency (Collage by NOAA/JPL-Caltech)
We are currently in Solar Cycle 25 which began in December 2019. Making the next maximum we will experience predicted to be between November 2024 and March 2025. However, as discussed by NASA scientists, the Sun’s activity has been ramping up quickly even though we have not yet reached peaked levels in this cycle. As solar activity increases it impacts our technology and communications on Earth.
Scientists work to improve our predictions of the strength and durations of solar cycles. Being able to predict solar cycles can help scientists forecast solar conditions, called space weather. Predicting and forecasting space weather can help scientists protect astronauts, space stations, satellites, as well as radio communications on Earth. As we will explore later, intense solar activity can affect us here on Earth.
Sunspots
As discussed previously, sunspots are areas on the surface of the Sun that appear darker. The reason that they appear darker is because they are cooler than other parts of the Sun’s surface. Though being cool on the Sun is still very hot, these sunspots have temperatures of around 6,500 degrees Fahrenheit (3,593 degrees Celsius) in comparison to an average surface temperature of 9,940 degrees Fahrenheit (5,504 degrees Celsius). Sunspots are cooler than the rest of the surface because they are areas where magnetic fields are particularly strong. So strong in fact that they keep some of the heat inside the Sun from reaching the surface.
Image Credit: NASA/SDO/AIA/HMI/Goddard Space Flight Center
Solar Flares
Near a sunspot, magnetic field lines often get tangled and then reorganized. When this happens, it can cause a sudden explosion of energy called a solar flare. Below is a video captured by NASA’s Solar Dynamics Observatory, the solar flare is the bright flash. You will also notice what appears like a large loop jumping off the right edge of the Sun, this is a coronal mass ejection.
Image Credit: NASA/SDO/Goddard
Coronal Mass Ejections
As perfectly depicted by this video, solar flares can sometimes be accompanied by a coronal mass ejection. These coronal mass ejections are giant bubbles of radiation and particles from the Sun that explode into space when the Sun’s magnetic fields suddenly reorganize. Solar flares and coronal mass ejections are the most powerful explosions in our solar system.
Can this Activity Affect Us Here on Earth?
It sure can! While the Sun is more than 93 million miles away, we feel its power every day in the form of heat and sunlight. However, sunlight and heat are not caused by the extreme events we looked at above. The Earth has a magnetic field that protects of from the majority of radiation and charged particles coming from the Sun. But what happens to Earth when something like a coronal mass ejection jumps off the surface of the Sun? The particles released in a coronal mass ejection are charged and if they make it to Earth they interact with our magnetic field. In simple cases this causes lights in the sky called auroras, or more often known as the Northern lights, though they are common in the South pole as well.
They occur most prominently near our poles because this is where the lines of our magnetic field converge. The gases in our atmosphere affect the colors we see. Oxygen gives off green and red light and nitrogen gives off purple and blue
Image Credit: NASA
Image Credit: International Space Station
In extreme cases a very strong coronal mass ejection’s charged particles can interfere with our power utility grids. In the worst cases they can cause power shortages and black outs. This is another reason why scientist work hard to predict solar activity. If we can predict when an extreme coronal mass ejection may hit Earth, we can prepare and hopefully prevent a lot of damage and protect lives.
Do Other Planets Get Auroras?
Yes, they do! These charged particles shot out from coronal mass ejections can travel extremely far. Auroras on Earth are a combination of an atmosphere and magnetic field interacting with the charged particles. So, if a planet has its own atmosphere and magnetic field then they too probably have auroras. We have been able to see auroras on Jupiter and Saturn.
Image Credit: NASA, ESA, and J. Nichols (University of Leicester)
Image Credit: ESA/Hubble, NASA, A. Simon (GSFC) and the OPAL Team, J. DePasquale (STScI), L. Lamy (Observatoire de Paris)
References
https://www.nasa.gov/feature/goddard/2016/picturing-the-sun-s-magnetic-field
https://spaceplace.nasa.gov/solar-activity/en/#:~:text=The%20Sun’s%20gases%20are%20constantly,things%20are%20a%20bit%20quieter.
https://spaceplace.nasa.gov/aurora/en/
https://spaceplace.nasa.gov/solar-cycles/en/
https://www.forbes.com/sites/jamiecartereurope/2022/08/02/the-sun-is-now-more-active-than-nasa-predicted-it-could-be-in-its-strongest-cycle-since-records-began/?sh=2fb00033cd59
https://www.nasa.gov/feature/goddard/2016/hubble-captures-vivid-auroras-in-jupiter-s-atmosphere
https://www.spaceweatherlive.com/en/solar-activity.html
https://esahubble.org/images/heic1815a/
