Arrival of sun ‘terminators’ triggers plasma tsunamis and birth of sunspots

25 Jul 2019

Image: © Peter Jurik/

Astrophysicists have found answers to some of the mysteries surrounding sunspot cycles with the discovery of events that trigger plasma tsunamis.

Scientists are able to predict a lot about our solar system, such as when a particular near-Earth object will pass by or when we can expect a lunar eclipse. Yet one phenomenon that remains very unpredictable is determining when one sunspot cycle ends and another begins.

Helping find an answer to this question, scientists have published two papers in the journals Solar Physics and Scientific Reports revealing how the death of one cycle triggers a tsunami of plasma to race through the sun’s interior, which gives birth to a new sunspot just a few weeks later.

One of the studies – based on solar observations over the past 140 years – identified ‘terminator’ events that mark the end of a sunspot cycle. By having an understanding of what to look for in the run-up to these terminators, the scientists predict that the current solar cycle will end in the first half of 2020 and kick-start another shortly after.

Meanwhile, the second study explored how the mechanism behind a terminator event could trigger the start of a new sunspot cycle using a sophisticated computer model. The resulting ‘solar tsunami’ could explain how the sun undergoes a rapid transition from one cycle to the next.

Evidence hidden for more than a century

“The evidence for terminators has been hidden in the observational record for more than a century, but until now we didn’t know what we were looking for,” said Scott McIntosh of the National Center for Atmospheric Research, who worked on both studies.

“By combining such a wide variety of observations over so many years, we were able to piece together these events and provide an entirely new look at how the sun’s interior drives the solar cycle.”

Better understanding the cycles of sunspots is crucial not just in our understanding of how the sun works, but also for us humans back on Earth. Sunspot activity is closely tied to solar storms – events that can disrupt Earth’s upper atmosphere and affect GPS signals, power grids and other critical technologies.

Explaining how these terminators were found, Bob Leamon, co-author of the first study and a scientist at the University of Maryland, said: “We were able to identify these terminators by looking at data from a whole range of different measures of solar activity – magnetic fields, spectral irradiance, radio flux – in addition to the bright points.

“The results demonstrate that you really need to be able to step back and use all the available data to appreciate how things work – not just one spacecraft or one observation or one model.”

Colm Gorey was a senior journalist with Silicon Republic