Aurora season is now fully underway around the Arctic circle. With the
end of northern summer approaching, dancing green lights are beaming
through the deepening polar twilight on a regular basis. Unlike lower
latitudes, the Arctic does not require a full-fledged geomagnetic storm
for aurora sightings.
Meanwhile, another polar phenomenon is on the wane: noctilucent clouds
(NLCs). Data from NASA's AIM spacecraft suggest that the northern
summer season for NLCs ended on or about August 26th. The "noctilucent
daisy" shown on http://spaceweather.com
will probably remain blank until November, when NLC activity shifts to
the southern hemisphere. NLCs are a summertime phenomenon and they
switch back and forth between the hemispheres accordingly. Stay tuned
for more electric blue ... in a few months.