Seeing the northern lights, or aurora borealis, typically requires travelling to frosty climes as far north as Norway or Iceland, but this year they have been visible in London, southern Europe and even Mexico. There were two big light shows, in May and October. While the October event was a result of a straightforward solar storm, scientists are puzzled about the storm that caused the May aurora.
“We’re still quite surprised how far south the aurora was seen,” says at the University of Reading, UK. “In terms of the geomagnetic impact, the storm was big, but not a 1-in-100-year storm.”
One interesting feature of May’s solar storm was that it wasn’t a single event, but several, says Owens. Unlike October’s light display, which was caused by a fairly typical large solar flare pointed directly at Earth, the May one was caused by smaller storms that interacted with and amplified each other on their way to Earth, he says. “It’s quite a different solar driver. It’s the same phenomenon, a big solar eruption, or what we call a coronal mass ejection, but from a series of events, rather than one big event.”
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May’s aurora also shows how hard it is to predict how space weather will affect Earth, says Owens. The link between the size of the solar flare, the resulting geomagnetic storm and where we see the northern lights is complicated and chaotic, he says.
Seeing two large solar storms in one year isn’t unusual, but there has been an alignment of factors that has meant we have seen more auroras, one of which is the time of day – after sunset – that the storm arrives, says at Lancaster University, UK.
Further auroras may be in store during the rest of which could continue for the next year.
