Hi Mark, here's a great how-to article on how to do just that. :-)
http://www.goalaskatours.com/winteractivities_northernlights_photoinfo.htmlBasically what you'll want to do is set your camera up on a tripod. Use a wide angle lens and a very large aperture. You'll be using a very long exposure (5+ seconds) so turn on "noise reduction" if your camera has that feature. Use a cable or timed shutter release instead of pressing the shutter button yourself. This will eliminate blur caused by the action of you depressing the button manually. Finally, set your camera's ISO to something slow like 100 for a nice smooth image. Remember that the actual amount of light will vary greatly so take lots of shots and vary your exposure time.
Have a blast! I'll be there with you in spirit. (I LOVE Alaska!)