It began with little fanfare in December 2019, just before COVID-19 became the never-ending story. A new solar cycle. Just so you know, it’s number 25 since we started paying attention to them, with cycle # 1 documented in 1755. The Sun has been going through cycles since it was born in a molecular cloud some 4.6 billion years ago. The cycle pattern has changed over time and will continue to change as our star ages. Currently, the average time of one full solar cycle is around 11 years. It varies though, so there is a consortium of astronomers who get together periodically to predict how the next cycle will run. Place your bets folks!
A brief refresher on solar cycles:
They are caused by the way our Sun rotates. OK, a little bit more. The Sun is made up of layers, like an onion of sorts, just fewer layers. Starting at its core, where the Sun’s fusion business takes place, each layer outward is less dense than the one below. This density differential allows each layer to slip past its neighboring layers and each has a different rotation rate. This slipping and sliding against each other generates intense magnetic fields. This same slippage causes some magnetic fields to curve, spiral, and twist around each other. Normally magnetic fields exit the Sun’s photosphere unseen, but the twisted fields carry a load of plasma, and that plasma is generally cooler than the photosphere. So, those areas look darker than the surrounding Sun. Sunspots! OK, you might ask, where is he going with this?
The number of daily sunspots correlates with solar activity and is used as an indicator. Astronomers keep careful records of daily sunspot numbers, and this lets them know when a cycle is heading toward maximum or minimum.
Increasing sunspots is a sign of more intense magnetic field interactions, as they wind up and become tangled, until a limit (solar maximum) is reached. Something’s got to give. That something is the Sun’s magnetic poles flip! Yes, they flip! It’s a massive tension release and the Sun starts to calm down, with fewer and fewer sunspots each day until…you guessed, solar minimum. It’s a long process, ramp-up to solar maximum takes around 5.5 years, then the magnetic pole flip, and around 5.5 years calming down to solar minimum. Repeat.
December 2019 was the official solar minimum, the end of Cycle 24, and the beginning of Cycle 25. The Cycle 25 maximum is expected to occur around 2025.
So far, sunspot numbers are exceeding prediction, meaning this cycle could be a showcase, with lots of spots, flares, and prominences. Auroras should be enhanced also. Fun for the whole family! It could make the October 14, 2023 annular and April 8, 2024 total solar eclipses more interesting too.
What’s in the Sky?
Early risers (well before sunrise): Look to the east-southeast-south and see four planets lined up (Venus, Mars, Jupiter, and Saturn). Soon there will be five as Mercury rises to join in.