Solar Storms Are “Sneeze-like” When They Reach Earth

Artist's impression of a coronal mass ejection. NASA

Understanding space weather allows us to better protect our electronics from dangerous solar storms. Unfortunately though, a new piece of research suggests things are even more complicated than we thought.

Scientists at the University of Reading have looked at coronal mass ejections (CMEs), large eruptions of plasma and magnetic flux responsible for geomagnetic storms. These CMEs should propagate following the magnetic field lines, but according to new research, they interact a lot more than expected with the solar wind and create structures similar to a sneeze.

The research, published in Scientific Reports, suggests that to truly plan against solar storms, we need to have a better picture of the Solar System. This includes our understanding of how solar winds are distributed in both time and space.

"Up until now, it has been assumed CMEs move like bubbles through space, and respond to forces as single objects. We have found they are more like an expanding dust cloud or sneeze, made up of individual plasma parcels all doing their own thing,” lead author Professor Mathew Owens said in a statement. "This means that trying to predict the shape and movement of CMEs as they pass through the solar wind becomes extremely difficult. Therefore if we want to protect ourselves from solar eruptions, we need to understand more about the solar wind."

The CMEs start by being moderately compact and expand as they move away from the Sun. As they expand, the magnetic forces become less and less strong, and they reach a point where they are expanding faster than the local wave speed. This is the reason why the phenomenon assumes a cloud-like appearance when it reaches Earth.

The CMEs actually stop being a coherent structure by the time they reach 44 million kilometers (28 million miles) from the Sun – that’s within the orbit of Mercury. Past that point, interactions with the environment only affect part of the CME, not the whole.

This finding might help us prepare for geomagnetic storms, which are temporary disturbances in the Earth’s magnetosphere caused by intense solar activity such as the CMEs.

The most powerful geomagnetic storm was the Carrington Event in 1859 and it was a sight to behold. It was responsible for aurorae from the poles to the tropics, and generated fires in telegraph stations across the US and Europe. If something like this were to happen today, the cost would be in the order of trillions of dollars for the US alone.

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