The Sun is the closest star to our planet in the Universe, and like many stars, it is far from quiet. Sunspots, many times the size of Earth, can appear on its surface and store enormous reservoirs of energy. And it is within these regions that huge explosions called solar storms occur. Solar storms are spectacular eruptions of billions of tonnes of hot gas travelling at millions of kilometres an hour. If they impact the Earth, they can produce beautiful displays of the aurora, but they can also cause problems with communication and navigation systems and power grids. In 1859, the largest solar storm ever observed – the so-called Carrington Event – erupted. Within hours, it generated displays of the aurora as far south as Italy and Cuba and caused interruptions in early telegraph systems in Europe and the US.
Our society is now even more dependent on technology, and solar storms have the potential to cause significant effect on their performance. In 2003, transformers in South Africa were damaged, while Swedish air traffic control systems were closed down in 2015 for more than an hour due to effects associated with a solar storm. More recently, emergency response communications were interrupted during hurricane season in September 2017 in the Caribbean, during the intensive solar storm period also studied in the Nature Astronomy paper. The Nature paper studied a particularly large solar storm on September 10, 2017, soon after the LOFAR station in Ireland had been turned on.
“Our results are very exciting as they give us an amazingly detailed insight into how solar storms propagate away from the Sun and where they accelerate fast particles with speeds close to the speed of light. These results may in the future help us to produce more accurate forecasts of when solar radio bursts occur and how the solar storm impacts the Earth”, said Dr Diana Morosan. At University of Helsinki, this work has been supported by the Finnish Centre of Excellence in Research for Sustainable Space (FORESAIL), where Dr Morosan currently works as a postdoctoral researcher as part of the Space Physics research group.
Understanding the acceleration of fast particles during solar storms is also one of the key science questions of the FORESAIL project. The results presented in the Nature Astronomy paper show that solar storms can accelerate these fast particles at multiple locations, in regions where storms drive a shock (regions where they travel faster than the speed of information travel in the solar atmosphere). These shocks in the solar atmosphere are the reason why so many particles are accelerated during solar storms, including the particles directed at Earth with potential space weather implications.
Dr Diana Morosan
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Associate Professor Emilia Kilpua
Multiple regions of shock-accelerated particles during a solar coronal mass ejection; Diana E. Morosan, Eoin P. Carley, Laura A. Hayes, Sophie A. Murray, Pietro Zucca, Richard A. Fallows, Joe McCauley, Emilia K. J. Kilpua, Gottfried Mann, Christian Vocks & Peter T. Gallagher . Nature Astronomy (2019) http://dx.doi.org/10.1038/s41550-019-0689-z