"Researchers call it the "Russell-McPherron effect." During the weeks around equinoxes, cracks form in Earth's magnetic field. Even a slight gust of solar wind can slip through to spark a light show--no geomagnetic storm required.
Because of this effect, September-October and March-April are the best times of year to catch auroras. The northern autumnal equinox is only 10 days away--so stay tuned. Aurora alerts: SMS Text. "
Thanks, Pete!