Auroras Love Equinoxes
On Sept. 23th the sun will cross the celestial equator heading south, marking the end of northern summer. That's good news for high-latitude sky watchers because, for reasons researchers do not fully understand, auroras love equinoxes. At this time of year when the seasons are changing, even gentle gusts of solar wind can spark a nice display of Northern Lights:
Harald Albrigtsen took the picture on Sept. 19th from Kvaløya, Norway. There was no geomagnetic storm predicted that night, and indeed no CME struck our planet. Instead a relatively minor fluctuation in the magnetic orientation of the solar wind sparked the display.
NOAA forecasters estimate a 30% chance of polar geomagnetic storms on Sept 21st, and the probability of Arctic auroras is probably even higher than that.