The Sun's magnetic cycle works much like planetary seasons, but on a vastly different timescale. During solar “summer,” otherwise known as solar maximum, our star becomes dramatically more active, sprouting dark sunspots across its surface and hurling massive flares into space. These solar storms send charged particles racing across the Solar System, creating the spectacular aurora displays. We’re currently experiencing this peak activity phase, with Solar Cycle 25 having possibly reached its maximum in 2024.
Conversely, solar "winter" brings a period of relative calm, with fewer sunspots and minimal solar storms. This 11 year pattern has puzzled scientists for decades because our Sun seemed unique among stars since other similar stars appeared to have magnetic cycles that were either much shorter or significantly longer, making our Sun appear to be an astronomical oddity.
The driving force behind the Sun's 11 year magnetic cycle lies deep within its churning interior, in a process called the solar dynamo. Unlike Earth, which rotates as a solid body, the Sun is a ball of plasma that spins faster at its equator than at its poles, we call this differential rotation. This uneven spinning, combined with the convection and churning of hot plasma rising from the Sun's core to its surface, acts like a massive magnetic field generator. As the Sun rotates, its magnetic field lines become twisted and tangled, building up magnetic energy until they eventually snap and reconnect in explosive events like solar flares. Over the course of about 11 years, this process completely reorganises the Sun's magnetic field, flipping its north and south magnetic poles before the cycle begins again.
This fundamental magnetic process is what researchers at Macquarie University, the University of New South Wales and the Chinese Academy of Sciences set out to study across different stars. Their work has challenged and perhaps overturned the assumption that the Sun’s 11 year cycle was unique among the stars. After analysing data from 138 stars like the Sun and collected data from multiple space telescopes over more than a decade, the researchers discovered that the behaviour of our Sun isn't unusual at all. The key insight came from studying stars at different life stages.
"We found several young Sun like stars with magnetic cycles similar to our sun, but shorter. As these stars age and slow down, they may evolve to have cycles like our Sun's current 11 year cycle.” - Dr. Chahal from the Macquarie University.
Studying stars at different stages of evolution acts rather like a time machine, offering glimpses into the Sun's past and future. Young, energetic stars display rapid magnetic cycles, but as they mature and their rotation slows, their magnetic behaviour evolves to match what we observe in our middle aged Sun today. This suggests that our Sun once had much more frequent magnetic cycles when it was younger and more active billions of years ago.
As we extend our reach into space with Mars missions on the horizon and become increasingly dependent on technology, understanding solar cycles becomes ever more crucial. Solar storms can disrupt GPS systems, interfere with airline communications, and knock out power grids on Earth. Pilots flying polar routes face heightened radiation exposure during solar maximum, requiring careful flight planning and monitoring. The risks are even greater for space travellers venturing beyond Earth's protective environment.
The spectacular auroral displays visible across unusually low latitudes over the past year serve as stunning reminders of our Sun's current active phase. But they also represent the complex magnetic processes that connect our star to Earth and influence everything from satellite operations to the paths airplanes take across the globe.