Alaska and the Aurora 2002




Perhaps the most wonderous celestial spectacle (next to a total solar eclipse, of course!) that one can witness is the aurora. Put simply, an aurora is what happens when high-energy, charged particles emitted by the Sun become trapped in the Earth's magnetic field, and in the course of spiraling down the magnetic field lines towards the Earth's magnetic poles, they excite nitrogen and oxygen atoms high up in the Earth's atmosphere, causing them to glow. When viewed from the northen hemisphere, the phenomena is known as the aurora borealis, or "Northern Lights"; when seen from Down Under, it is known as the aurora australis, the "Southern Lights", but in fact the two have been shown to be almost mirror images of each other.

Aurorae are visible almost every night from somewhere on the planet, but to optimise your chances of seeing one, it helps if:

  1. the Sun is particularly active. The Sun goes through cycles of activity, peaking every 11 years or so. One manifestation of this is that the number of sunspots rises and falls with a period of 10-12 years. The number and strengths of solar flares, which can send huge numbers of energetic particles towards Earth (where they arrive between 2 and 3 days later) is known to follow the same cycle, but usually lags the peak in sunspot numbers by a couple of years or so. The last "solar maximum" occurred in 2000, so the peak in auroral activity can be expected to occur through 2002-2003.
  2. you live under the "auroral oval", which is centered on the geomagnetic pole, and not the geographic pole. In the northern hemisphere, the auroral oval usually extends across Alaska and northern Canada, the southern tip of Greenland and Iceland, and the northern coast of Norway.
  3. you observe from a dark-sky site, well away from city lights.
  4. you stay up late. Auroral activity occurs day and night, but is usually observed to peak between about 11pm, and 3am.

Not long after returning from the excellent Turkey eclipse of 1999, Dave Moser bagan planning an aurora viewing expedition to Alaska in 2002 (as with solar eclipses, it pays to plan ahead!). I said I'd love to go; as a young lad growing up in Dunedin, New Zealand (at a latitude of 46o S) during a previous solar maximum in the early 1980s, I still vividly recall some stunning displays of the aurora australis. One of the drawbacks of living in big cities at more temperate, mid-latitudes (as I do now) is that opportunities to see an aurora are few and far between. Besides, I'd always wanted to see the "Last Frontier", and by now, I'd almost forgotten what sub-zero temperatures felt like...

On March 8 2002, "Dave's Dozen" met up in Anchorage, and off we went in search of the aurora...

You should also check out Dave Moser's collection of images from the trip.

Lots more information about aurorae can be found at the University of Alaska Fairbanks Geophysical Institute. UAF run a great museum in Fairbanks, well worth a visit. We found the aurora forecasts provided by Space Weather.com to be particularly helpful. Lots of other great aurora photographs from Alaska can be found at Dick Hutchinson's site, and at Dennis Mammana's site.


Last modified 11 May 2002 by Stuart Ryder