Παρασκευή 18 Δεκεμβρίου 2015

aurora borealis

“Autumn is special in part because lengthening nights and crisp pleasant evenings tempt stargazers outside; they see things they ordinarily wouldn’t. But there’s more to it than that: autumn really does produce a surplus of geomagnetic storms–almost twice the annual average.In fact, both spring and autumn are good aurora seasons. Winter and summer are poor. This is a puzzle for researchers because auroras are triggered by solar activity. The Sun doesn’t know what season it is on Earth–so how could one season yield more auroras than another?” (Nasa)

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