The most recent image of the Sun, taken by NASA's Solar Dynamic Observatory at 10:45 UTC on August ... [+]
Not only is Earth suddenly spinning faster, but our Sun is getting more active than NASA predicted.
The Sun appears to have a cycle of about 11 years during which it waxes and wanes. Its activity is measured by the number of sunspots on its surface, which have been counted each day since 1755.
During that 11-or-so years there’s a “solar minimum” (when there are the fewest sunspots) and a “solar maximum” (when there are the most sunspots).
Solar Cycle 25 ramps up
We’re now in Solar Cycle 25, which began in December 2019 when, in retrospect, solar scientists were able to tell the moment of solar minimum. Not surprisingly, solar maximum is predicted to occur midway through Solar Cycle 25, so between November 2024 and March 2026—and most likely July 2025.
“The Sun’s activity has quickly ramped up and even though we haven’t reached peak levels in this cycle, the Sun’s activity is already exceeding predictions,” said Nicola Fox, Director of NASA’s Heliophysics Division in a blog last week. “Solar events will continue to increase as we near solar maximum in 2025, and our lives and technology on Earth, as well as satellites and astronauts in space, will be impacted.”
The most recent images of the Sun, taken by NASA's Solar Dynamic Observatory on August 2, 2022.
The effect of ‘space weather’
More activity on the Sun’s surface means more solar flares and solar eruptions, which put more charged particles into space.
This space weather, when directed at Earth, can mean interruptions to radio signals, surges in electricity grids, damage to GPS satellites and risks to spacecraft and astronauts on the International Space Station.
However, exactly how many sunspots there will be during solar maximum—and, therefore, how active our Sun will get during the peak of this current cycle—is unknown.
NASA’s prediction for Solar Cycle 25
Solar Cycle 24 was very muted. Its solar maximum occurred in April 2014 when sunspots peaked at 114. The average is 179. Solar Cycle 25 Prediction Panel—an international group of experts co-sponsored by NASA and National Oceanic and Atmospheric Administration (NOAA) predicted that Solar Cycle 25 would also be below average in terms of solar activity.
It’s not working out that way.
The more charged-up the solar wind headed towards Earth, the brighter and more frequent are displays of aurorae. Cue an intense season of Northern Lights last winter and spring, which has been the most obvious visual effect of more intense space weather and increased geomagnetic activity.
In fact, December 2021 saw over twice the number of sunspots predicted—67 to the expected 26.
The 2nd July 2019 Total Solar Eclipse in Chile was an amazing astronomical event. At Atacama Desert ... [+]
What is the ‘solar clock’ model?
It therefore seems that a rival prediction from another group of scientists at the National Center for Atmospheric Research (NCAR) is coming true. Contrary to the Solar Cycle 25 Prediction Panel, these researchers predicted that the maximum sunspot number will be somewhere between 210 and 260.
It that happens then the researchers’ explanation—the “solar clock” theory that observes that the Sun has overlapping 22-year magnetic cycles that interact to produce the 11-year Solar Cycle—could gain credence. It suggests a new method for deciphering when solar cycles begin and end as well as suggesting that shorter cycles are followed by more active ones.
A rival model emerges
Another model published today also suggests that solar cycles comes in pairs.
However, it argues that the number of sunspots three years before solar minimum in an odd-number solar cycle is associated with the number of sunspots of the following solar cycle’s solar maximum. Using that model the researchers at the Central Astronomical Observatory at Pulkovo, Saint-Petersburg, Russia predict that this current Solar Cycle 25 will reach solar maximum next year with 154 sunspots and remain more of less the same through 2024, which puts it somewhere between the NASA/NOACC predication and that of NCAR.
With so many different models and predictions around what actually happens could make it easier in future for solar physicists to predict solar activity more accurately.
As a bonus a strong Solar Cycle 25 could mean a particularly spiky-looking solar corona around solar maximum. That’s good news for sky-watchers in North America because there will be a total solar eclipse on April 8, 2024, the totality period of which can be viewed perfectly safely with the naked-eye.
Wishing you clear skies and wide eyes.
