Wednesday, July 12, 2017

Aurora Hunting

I wrote this for submission to some travel and astronomy magazines.  No interest, so I thought I would share it with you.
Northern Lights Planning
The Aurora Borealis (Latin for “northern dawn”) is among the most awe-inspiring natural phenomena, comparable in my experience to a total solar eclipse.  You get dancing displays of green, pink, and gray, with curtains shimmering in the cold night sky, often appearing and disappearing every few seconds. 
How do you improve your odds of seeing them?  There is a widely held belief that seeing them on a vacation is largely random.  Northern Lights tours are offered, but unless your tour includes a full 28 day solar rotation cycle, your odds are not spectacular.  This article provides some planning advice for those who can’t afford 2-4 weeks of travel hoping to see them, or like having more control over their vacations.
My wife and I have made two Northern Lights trips in the last few years: one to Edmonton that failed (for reasons that caused me to research the topic in more detail), and one to Fairbanks that was a complete success.  Here’s what I learned about how to make a successful and reasonably priced trip.
There are several factors that determine Northern Lights visibility: solar storm activity; geomagnetic latitude; dark skies; clear skies; and topography.

Solar Storm Activity

This is of course the most important (because solar storms cause the Northern Lights) and the hardest to predict long-term.  The University of Alaska, Fairbanks has a website showing short-term aurora forecasts which are accurate for several upcoming days (http://www.gi.alaska.edu/AuroraForecast).  Arranging airfares for a few days in advance is very expensive.  Fortunately, the Sun rotates about every 28 days, so if March 1 has strong solar storm activity, March 29, plus or minus a few days, is very likely to have a good display.  Plan to arrive a couple days before the next likely peak and stay a couple days past.

Geomagnetic Latitude


Northern Lights are caused by charged particles from the Sun falling into the Earth’s magnetic field where it is weakest, near the Earth’s magnetic poles.  The north magnetic pole is currently near Elsmere Island in northern Canada; distance from that point determines where the Northern Lights can be seen.  Generally, across central Alaska, northern Canada, southern Greenland, Iceland, northern Scandinavia, and northern Russia.  This diagram is from the University of Alaska, Fairbanks web site:
On rare occasions with very strong solar storms, you may even see auroras in the southern U.S.

Dark Skies

The auroras are always present, but if the sky is bright (such as daytime or twilight) you won’t see them.  You need nighttime, preferably with a New Moon, or at least at first or third quarter, and away from city lights.  Complicating this, nights are longest in the northern latitudes in the depths of winter, when standing outside at night is not very pleasant.  This website shows sunrise, sunset, and twilight times for any city, as well as upcoming Moon phases: https://www.timeanddate.com/.
We went to Fairbanks in late April, at a New Moon, because it was only freezing at night.  While city lights are bad, when we arrived at our lodgings in Fairbanks, at 2:00 AM, there was a green aurora visible over the parking lot.  Driving out of town about forty miles dramatically improved our view.  We stayed up until midnight before heading out; in retrospect, setting an alarm for 2:00 AM, then loading up on coffee before heading out makes more sense.  The sky was lightening up by 3:30 AM in late April, so early rising may not work except in the depths of winter.  As spring arrives in the polar regions, this bright sky late into the night and in the early morning produces an effect called “white nights” by the Russians.

Clear Skies

Clouds are obviously a problem.  The light from the auroras comes from 60 to 200 miles up—far above the clouds.  https://weatherspark.com/ provides average temperatures and cloud cover based on historical data.  I see that we were unusually fortunate on cloudiness for our April trip.

Topography

Our experience was that the Northern Lights in Fairbanks were generally high in the sky, from 45o to 90o above the horizon.  Depending on your geomagnetic latitude, they may be lower.  Being in a valley or surrounded by trees along a road will therefore block your view.  High points are a good choice.  Chena Hot Springs, well east of Fairbanks with very dark skies, provides aurora tours that take you to mountaintops.  Instead, we were at the side of a lonely highway south of Fairbanks on the edge of a vast forest.  Warning: Grizzly bears and wolves are active at night in the forests; being disemboweled will ruin your Northern Lights trip.

Planning Your Aurora Trip

As you can see, there is a bit of work required to combine reasonable airfares with a high probability of seeing auroras. 

Pictures

These single exposures were shot with a Pentax K10D at f/8, with a 52mm lens, ISO 1600, 30 second exposure.  A camera with a higher ISO range would have worked much better, and made time lapse photography effective.









1 comment:

Rich Rostrom said...

"Elsmere Island in northern Canada"...

ITYM Ellesmere Island.