17 Sep Solar termination events
Last Updated on September 29, 2022
Solar termination events
It sounds rather drastic, but our sun has just experienced a termination event. A quick glance outside indicates there’s still plenty of sunlight, so what is a solar termination event?
The termination event determines when solar cycles begin and end and in February 2022, we officially said goodbye to solar cycle 24 according to solar physicists Scott McIntosh and Bob Leamon form the University of Maryland.
Every 11 years or so, the Sun’s magnetic field completely flips and is what we call the solar cycle. This means that the Sun’s north and south poles switch places. Then it takes about another 11 years for the Sun’s north and south poles to flip back again.
When one solar cycle ends and the next begins, the sun may experience cataclysmic magnetic field collisions known as terminator events resulting in massive waves of plasma that can charge across the sun’s surface for weeks at a time.
The new solar cycle 25 is judged by NASA and NOAA to have begun in December 2019. However, old Solar Cycle 24 refused to go away. It hung on for two more years, producing occasional old-cycle sunspots and clogging the sun’s upper layers with its decaying magnetic field. During this time, the two cycles coexisted with Solar Cycle 25 struggling to break free while old cycle 24 held it back.
Researchers have long known that solar cycles can overlap.
Scientists at the National Center for Atmospheric Research (NCAR) predict that when oppositely-charged bands of magnetism collide at the Sun’s equator, they obliterate each other—they “terminate.” Below you can see bands of coronal bright points or hot spots in the sun’s atmosphere, linked to old Solar Cycle 24 vanishing in December 2021, signalling a Termination Event.
The timing of the Termination Event can predict the intensity of the new cycle. McIntosh and Leamon looked back over 270 years of sunspot data and found that Termination Events happen every 10 to 15 years.
Solar physics is poorly understood, with the importance and interplay of various observed cycles not fully understood. They found that the longer the time between terminators, the weaker the next cycle would be. Conversely, the shorter the time between terminators, the stronger the next solar cycle would be.
MacIntosh says Solar Cycle 25 will be just above the historical average with a monthly smoothed sunspot number of 190 ± 20.
This prediction is a sharp departure from NOAA’s official forecast of a weak solar cycle. It could be just enough to catapult Terminators into the forefront of solar cycle prediction techniques. So why is there so much conjecture about the strength/or not of solar cycle 25? “It is a bit like a decadal sport to predict the cycle,” said McIntosh. “Stoking it this time may be the strong contrast between what our work is showing versus the weak consensus prediction.”
This is important because extreme space weather can cause problems for communication networks, satellites, power distribution networks, aviation and astronauts. Understanding the Sun and its cycles is key to predicting space weather.