Scientists from Australia and the United States have solved a long-standing enigma about the Sun, which might aid astronomers in forecasting space weather and preparing for potentially disastrous geomagnetic storms if they strike Earth.
Solar flares, sunspots, and coronal mass ejections may all induce space-weather streams of high-energy particles from the Sun, which can cause geomagnetic storms. However, it is unclear how these occurrences occur, and it is hard to anticipate when they will occur.
Now, new research conducted by Dr. Geoffrey Vasil of the University of Sydney’s School of Mathematics and Statistics might give a solid theoretical foundation for better understanding the Sun’s core magnetic dynamo, which helps produce near-Earth space weather.
The characteristics of magnetic dynamos, such as the Sun, are known to be entirely altered by strong rotation.
Dr Vasil
The Sun is divided into various zones. The convection zone is one of the most notable features of the star, consisting of a 200,000-kilometer-deep ocean of super-hot rolling, turbulent fluid plasma that covers the outer 30 percent of the star’s diameter.
According to current solar theory, the greatest swirls and eddies take up the convection zone, which NASA depicts as gigantic circular convection cells.
The ‘Convective Conundrum’ is a long-standing dilemma in which these cells have never been discovered.
Dr Vasil said there is a reason for this. Rather than circular cells, the flow breaks up into tall spinning cigar-shaped columns just 30,000 kilometers across. This, he said, is caused by a much stronger influence of the Sun’s rotation than previously thought.
“You can balance a skinny pencil on its point if you spin it fast enough,” said Dr Vasil, an expert in fluid dynamics. “Skinny cells of solar fluid spinning in the convection zone can behave similarly.”
The findings were reported in the Proceedings of the National Academy of Sciences.
“We don’t know very much about the inside of the Sun, but it is hugely important if we want to understand solar weather that can directly impact Earth,” Dr Vasil said.
“The characteristics of magnetic dynamos, such as the Sun, are known to be entirely altered by strong rotation.”
This predicted rapid rotation inside the Sun, according to Dr Vasil and collaborators Professor Keith Julien of the University of Colorado and Dr Nicholas Featherstone of the Southwest Research Institute in Boulder, suppresses what would otherwise be larger-scale flows, resulting in more variegated dynamics for the outer third of the solar depth.
“By properly accounting for rotation, our new model of the Sun fits observed data and could dramatically improve our understanding of the Sun’s electromagnetic behavior,” said Dr Vasil, who is the lead author of the study.
Solar geomagnetic storms can, in the most extreme situations, deluge the Earth with radiation pulses capable of damaging our sophisticated global electronics and communication systems.
The Carrington Event, a massive geomagnetic storm of a similar sort, struck Earth in 1859, although this was before our global reliance on electronics. The telegraph system from Melbourne to New York, which was still in its infancy, was harmed.
“A similar event today could destroy trillions of dollars’ worth of global infrastructure and take months, if not years, to repair,” Dr Vasil said.
In 1989, a small-scale incident in Canada resulted in extensive blackouts, which some initially mistook for a nuclear assault. A solar storm on the size of the Carrington Event passed Earth in 2012 without causing any damage, missing our orbit around the Sun by by nine days.
“The next solar max is in the middle of this decade, yet we still don’t know enough about the Sun to predict if these cyclical events will produce a dangerous storm,” Dr Vasil said.
“While a solar storm hitting Earth is very unlikely, like an earthquake, it will eventually happen and we need to be prepared.”
Solar storms can take from hours to days to reach Earth after erupting from the Sun. Dr. Vasil believes that a greater understanding of our home star’s underlying dynamics might help planners avert tragedy if they have adequate warning to shut down equipment before a burst of energetic particles takes over.
“We cannot explain how sunspots form. Nor can we discern what sunspot groups are most prone to violent rupture. Policymakers need to know how often it might be necessary to endure a days-long emergency shutdown to avoid a severe catastrophe,” he said.
To enhance the modeling of the Sun’s internal activities, Dr. Vasil and his colleagues’ theoretical model will now need to be tested by observation. To do so, scientists will employ helioseismology, a technique that involves listening within the star’s beating heart.
“We hope our findings will inspire further observation and research into the driving forces of the Sun,” he said.
This might include the first launch of polar orbiter observational satellites outside the Solar System’s elliptical plane.
