A team of scientists have made a groundbreaking advancement in predicting solar activity, pioneering the development of a novel Sun clock that provides fresh insights into the seasons of our star.
The Sun clock, developed in a study by a team of researchers at the University of Warwick, provides the most comprehensive understanding to date of solar activity, uncovering in unprecedented detail the intricacies and timescales of the Sun’s seasons. The discovery not only enhances our knowledge of the Sun’s behaviour but may also aid in mitigating the effects of solar activity on a plethora of Earth and space-based technologies.
The research is published in The Astrophysical Journal.
Impacts of solar activity
When violent solar activity occurs on the Sun, this can have a considerable knock-on effect on our planet, causing some of Earth’s most severe space weather events. These ferocious storms of solar activity have the potential to disrupt, damage, and even destroy a range of technologies, such as communication systems, satellites, power distribution, and aviation.
Solar activity follows a cycle of around 11 years and is comprised of three seasons, all of which have varying effects on the space weather experienced on Earth. The first season is called the solar maximum; here, the Sun is active and disordered, making space weather events erratic and stormy. Next is the declining phase, where both the Sun and solar wind become more ordered, and space weather becomes more moderate. The final season is the solar minimum, where activity is quiet.
Designing the Sun clock
To thoroughly investigate the solar seasons, the researchers employed data from the daily sunspot number record that has been available since 1818, which enabled them to design and fabricate their revolutionary device that maps the irregular solar cycles onto a regular clock – the Sun clock. The Sun’s magnetic polarity reverses every 11 years on average, giving it a 22-year magnetic cycle, which led to the scientists creating a 22-year cycle for their clock to explore this. The researchers applied data of the Sun’s magnetic polarity into the clock by utilising continuous records of geomagnetic activity over the last 150 years, all of which resulted in in-depth and versatile observations of seasonal solar activity.
The unprecedented detail of the Sun clock allowed the scientists to observe that the solar activity changing from the solar maximum to the declining phase was extremely fast, occurring in just a few solar rotations (27 days). They also ascertained that the declining phase is twice as long in even-numbered solar cycles than in odd-numbered cycles, with no two solar cycles being identical in terms of amplitude or duration. The duration of the declining phase also differs in duration depending on whether the Sun’s magnetic polarity is up or down. Currently, we are close to entering cycle 25, meaning that the next declining phase will be short.
Professor Sandra Chapman, the lead author of the study from the University of Warwick Department of Physics, said: “By combining well-known methods in a new way, our clock resolves changes in the Sun’s climate to within a few solar rotations. Then you find the changes between some phases can be really sharp.
“If you know you’ve had a long cycle, you know the next one’s going to be short; we can estimate how long it’s going to last. Knowing the timing of the climate seasons helps to plan for space weather. Operationally it is useful to know when conditions will be active or quiet for satellites, power grids, communications.
“I also think it is remarkable that something the size of the Sun can flip its magnetic field every 11 years and going down-up is different to going up-down. Somehow the Sun knows which way up it is, and this is an intriguing problem, at the heart of how the Sun generates its magnetic field.”
