Archive for August, 2010

The Start of the Alaska Aurora Season?

Wednesday, August 4th, 2010

Good news for those who like to view the aurora borealis (northern lights). There has been recent solar activity that has good potential for a decent display tonight (August 4-5). In a larger sense, the overall solar activity seems to be picking up after several quiet years. Activity on the sun, e.g. sunspots and solar storms, corresponds to aurora displays here on earth.

When are the northern lights visible?

This is a common question I hear from visitors from outside Alaska. Some are under the impression that it must be cold for the aurora to be visible. In actuality, to see the aurora, three things have to coincide: It must be dark enough. It must be clear enough. There needs to be an aurora over your part of the world. By the way, in Alaska, when it is dark and clear, it is indeed most likely is cold.

1) Darkness. This is the easiest of the three. Alaska’s “midnight sun” makes it difficult or impossible to see the lights for a good part of the year. That’s mainly what I’m getting at with the idea of a “season.” In most of Alaska, August through April or early May are the only months when it gets dark enough. This varies by latitude, with April and August being too light in Barrow (northernmost city), and at least some year ‘round darkness in Adak (southernmost city, in the Aleutians). We’re into that time of the year. For detailed information on sunrise, sunset, and more importantly, twilight times, head to the US Naval Observatory Astronomical Applications web site.

2) Clear weather. Obviously this changes on a more-or-less frequent basis. Scattered or thin clouds are OK and might even make interesting patterns. Take a look at the sky.  How’s it look for tonight? Quite cloudy for south-central and most of western Alaska, not bad for parts of the interior, especially the east side. In Southeast Alaska, skies are spectacularly clear almost everywhere (contrary to our reputation), but the weather system that is smothering Southcentral is heading our way, so by darkness tonight the outer coast may be already clouding up. For updated cloud cover information, satellite photos plus some local forecasts are a good start.

Thermal IRClick for latest satellite photo and forecasts from the NWS Anchorage.

3) Auroral activity. As mentioned above, the level of solar activity, along with its position on the sun influences this factor. We’ve been in a extended solar activity minimum for several years that finally seems to be ending. This graphic from NASA shows the progression of the sunspot cycle, a measure of solar activity.

ssn_predict_l Click for NASA’s web page containing this image (click on the bottom graph on the linked page–the one labeled predition–the thumbnail looks different than what you see here).

How about tonight, or the next few days? Here’s the short term aurora forecast from the Geophysical Institute at the University of Alaska Fairbanks issued 4 August 2010. Valid for 4 and 5 August.

aurora forecast mapClick for the latest forecast.

More Links:

http://cleardarksky.com/csk/ A unique service which forecasts criteria 1 and 2 above.

http://www.swpc.noaa.gov/index.html NOAA’s Space Weather Prediction Center.

http://www.spaceweather.com/ This useful site has a service to send you an email when solar activity heats up.

http://www.exploratorium.edu/learning_studio/auroras/index.html Good stuff for primary and secondary teachers.

http://latitude64photos.com/ Great aurora photography by former Alaskan climatologist Jan Curtis.

http://www.eaglevalleyphoto.com Includes some nice aurora photos from Haines.

So, here’s hoping for a good aurora borealis (or australis if you’re from down under) viewing season, especially before it gets too cold. I’d love to hear of your aurora watching experiences and photos. Please use the blog comment form.