What’s Going On With The Sun?
What’s Going On With The Sun?
By now, you probably already know that we are going to have a total solar eclipse here in Evansville on April 8th. For a total solar eclipse to occur, the Earth, Moon, and Sun have to fall into perfect alignment, circumstances that are not only rare, but also spectacular to witness. But something unexpected appears to be going on inside the Sun that may make the solar eclipse on April 8th a true once in a lifetime experience.
Just like the seasons here on Earth, or the phases of the Moon, the Sun goes through cycles. Each solar cycle lasts approximately 11 Earth years, coinciding with the reversal of the Sun’s magnetic poles. At the start of its cycle, the Sun is quiet and inactive. As the cycle progresses, the Sun’s activity increases, reaching a peak halfway through the cycle. The Sun’s activity then decreases, returning to its quiet state before the start of a new solar cycle.
During the Sun’s peak activity, known as solar maximum, solar flares, prominences, and coronal mass ejections are more common. Each of these structures are caused by the shifting magnetic field lines that emanate from the Sun.
Solar flares occur when a burst of electromagnetic radiation is suddenly released from the Sun’s corona (its upper layer of atmosphere). Traveling at the speed of light, solar flares reach the Earth only 8 minutes after they leave the Sun. While not generally harmful to life on Earth, particularly strong solar flares can temporarily scramble short-wave radio communication.
A solar prominence, with the Earth for scale.
Solar prominences are large loops of plasma arching away from the Sun along its magnetic field lines. During a total solar eclipse, prominences can be seen as bright red bursts of material just along the surface of the Sun. While typically remaining attached to the Sun, solar prominences can be ejected from the Sun and flung out into space. If this occurs, they are reclassified as coronal mass ejections.
A photo of aurorae taken from the International Space Station. These aurorae were likely caused by a coronal mass ejection that triggered geomagnetic storms on Earth.
Coronal mass ejections are massive structures of plasma and magnetic flux that are emitted from the Sun when it is at its most active. If ejected towards Earth, coronal mass ejections can cause geomagnetic storms, brilliant aurorae (Northern Lights), and even damage power grids here on Earth. Near solar maximum, scientists can observe multiple coronal mass ejections every day.
So what does this have to do with the total solar eclipse on April 8th? Our current solar cycle began in December of 2019. From that point, activity has been ramping up, with a predicted peak sometime in mid-2025. But here is the catch: nature doesn’t always play by the rules. This solar cycle has been far more intense than predicted, and solar activity appears to be reaching a peak earlier than anticipated (check out the NOAA solar cycle progression webpage for more details). Scientists now think we could be very close to solar maximum on April 8th. If true, totality will reveal a stunning patchwork of prominences and flares along the surface of the Sun. If we get really lucky, a coronal mass ejection will coincide with the eclipse, possibly triggering aurorae visible during totality.
The Sun’s highly active state could result in a truly extraordinary sight during the eclipse. With any luck, we will be able to see this stunning display with the naked eye. So cross your fingers that the only storms we see on April 8th are those on the Sun!