SOLAR SECTOR BOUNDARY CROSSING: On Sept. 3rd

Earth will cross a fold in the heliospheric current sheet–a vast wavy structure in interplanetary space separating regions of opposite magnetic polarity. This is called a "solar sector boundary crossing," and it could trigger geomagnetic activity around Earth's poles. Arctic sky watchers should be alert for auroras when the crossing occurs.

http://www.spaceweather.com/