Scientists at the University of Sydney and in the U.S. 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, reports Phys.org. The Sun’s internal magnetic field is directly responsible for space weather – 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. A new study led by Dr. Geoffrey Vasil from the School of Mathematics & Statistics at the University of Sydney could provide a theoretical framework to improve our understanding of the Sun’s 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 – a 200,000-kilometre-deep ocean of turbulent fluid plasma taking up the outer 30 percent of the star’s diameter. Existing solar theory suggests the largest swirls and eddies take up the convection zone, imagined as giant circular convection cells. However, these cells have never been found, a long-standing problem known as the “Convective Conundrum”. Vasil said there is reason for this. Rather than circular cells, the flow breaks into tall, spinning, cigar-shaped columns “just” 30,000 kilometres 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 Vasil. “Skinny cells of solar fluid spinning in the convection zone can behave similarly. 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. Strong rotation is known to completely change the properties of magnetic dynamos, of which the Sun is one.” 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 from Melbourne to New York was affected. Said Vasil: “A similar event today could destroy trillions of dollars worth of global infrastructure and take months, if not years, to repair.” A small-scale event in 1989 caused massive blackouts in Canada in what some initially thought might have been a nuclear attack. In 2012, a solar storm similar in scale to the Carrington Event passed by Earth without impact, missing our orbit around the Sun by just 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. Solar storms emerging from within the Sun can take from several hours to days to reach Earth. 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.
https://phys.org/news/2021-08-solar-puzzle-earth-planet-wide-blackouts.html
