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Scientists at the University of Sydney and in the USA have solved a long-standing mystery about the Sun that could help astronomers predict space weather and help us prepare for potentially devastating geomagnetic storms if they were to hit Earth.

The Sun鈥檚 internal magnetic field is directly responsible for space weather 鈥� streams of high-energy particles from the Sun that can be triggered by solar flares, sunspots or coronal mass ejections that produce geomagnetic storms. Yet it is unclear how these happen and it has been impossible to predict when these events will occur.

Now, a new study led by聽聽from the聽聽at the University of Sydney could provide a strong theoretical framework to help improve our understanding of the Sun鈥檚 internal magnetic dynamo that helps drive near-Earth space weather.

The Sun is made up of several distinct regions. The convection zone is one of the most important 鈥� a 200,000-kilometre-deep ocean of super-hot rolling, turbulent fluid plasma taking up the outer 30 percent of the star鈥檚 diameter.

Existing solar theory suggests the largest swirls and eddies take up the convection zone, imagined as giant circular convection cells as聽聽(and published below).

However, these cells have never been found, a long-standing problem known as the 鈥楥onvective Conundrum鈥�.

Dr Vasil said there is a reason for this. Rather than circular cells, the flow breaks up into tall spinning cigar-shaped columns 鈥榡ust鈥� 30,000 kilometres across. This, he said, is caused by a much stronger influence of the Sun鈥檚 rotation than previously thought.

鈥淵ou can balance a skinny pencil on its point if you spin it fast enough,鈥� said Dr Vasil, an expert in fluid dynamics. 鈥淪kinny cells of solar fluid spinning in the convection zone can behave similarly.鈥�

The findings have been published in the聽.

鈥淲e don鈥檛 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,鈥� Dr Vasil said.

鈥淪trong rotation is known to completely change the properties of magnetic dynamos, of which the Sun is one.鈥�

Dr Vasil and collaborators聽聽of the University of Colorado and聽聽at Southwest Research Institute in Boulder, say that this predicted rapid rotation inside the Sun suppresses what otherwise would be larger-scale flows, creating more variegated dynamics for the outer third of the solar depth.

鈥淏y properly accounting for rotation, our new model of the Sun fits observed data and could dramatically improve our understanding of the Sun鈥檚 electromagnetic behaviour,鈥� said Dr Vasil, who is the lead author of the study.

In the most extreme cases, solar geomagnetic storms can shower the Earth with pulses of radiation capable of frying our sophisticated global electronics and communication infrastructure.

A huge geomagnetic storm of this type hit Earth in 1859, known as the Carrington Event, but this was before our global reliance on electronics. The fledgling telegraph system聽听迟辞听聽was affected.

鈥淎 similar event today could destroy trillions of dollars鈥� worth of global infrastructure and take months, if not years, to repair,鈥� Dr Vasil said.

A small-scale event in 1989 caused聽聽in what some initially thought might have been a nuclear attack.聽聽similar in scale to the Carrington Event passed by Earth without impacting, missing our orbit around the Sun by just nine days.

鈥淭he next solar max is in the middle of this decade, yet we still don鈥檛 know enough about the Sun to predict if these cyclical events will produce a dangerous storm,鈥� Dr Vasil said.聽

鈥淲hile a solar storm hitting Earth is very unlikely, like an earthquake, it will eventually happen and we need to be prepared.鈥�

Solar storms emerging from within the Sun can take from several hours to days to reach Earth. Dr Vasil said that better knowledge of the internal dynamism of our home star could help planners avoid disaster if they have enough warning to shut down equipment before a blast of energetic particles does the job instead.

鈥淲e 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,鈥� he said.

Dr Vasil and his colleagues鈥� theoretical model will now need to be tested through observation to further improve the modelling of the Sun鈥檚 internal processes. To do this, scientists will use a technique known as helioseismology, to listen inside the beating heart of the star.

鈥淲e hope our findings will inspire further observation and research into the driving forces of the Sun,鈥� he said.

This could involve the unprecedented launch of polar orbiter observational satellites outside the elliptical plane of the Solar System.

Declaration

Dr Geoffrey Vasil received no additional funding for this paper. Professor Keith Julien acknowledges support from NASA and the US National Science Foundation. Dr Nicholas Featherstone also acknowledges support from NASA.