Blue View - The Northern Lights
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Seeing the northern lights, or Aurora Borealis, has been on Marcie’s bucket list for a long time, and one of the goals of our long road trip through Canada and Alaska was to finally experience this celestial phenomenon ourselves. Now that it’s September and the nights are getting longer, the odds of seeing them are increasing daily.
On our way north, we passed through the small town of Watson Lake in the Yukon Territory, which is known for two things: the Signpost Forest, with its approximately 100,000 signs, nailed up over the years by seemingly every passerby, including us, since the Alaska Highway was being built in 1942; and the Northern Lights Planetarium. The planetarium provides a spectacular presentation of the northern lights in all its glory… and we didn’t have to wait up half the night in -40° weather to watch it. Technically, then, I’d say we did see the northern lights in Canada, but I suspect Marcie is still going to insist on seeing the other, outside version.
Here are more images. Click on any one to see the full size version.
History
Throughout history, there have been many references to the northern lights. Most sources credit the Italian astronomer Galileo Galilei as the first to coin the name Aurora Borealis in 1619. Other sources claim that a French philosopher, scientist and astronomer named Pierre Gassendi, who was a friend of Galileo, named the phenomenon after observing a spectacular display in France in 1621. There are also several explanations for the etymology of the name, but the one that seems most likely to me is that the name probably translates from 15th century Latin: Aurora, meaning dawn, and borealis, meaning north or northern… thus ‘Northern Dawn’.
The earliest possible reference is thought to be a depiction of it among the 30,000 year old Cro-Magnon cave paintings in Lascaux, France, shown below and named the “macaronis”. (I defer to the more learned experts who determined that this is likely a drawing of the Aurora Borealis. As with many ancient pictographs and drawings, I have trouble understanding what is being depicted.) Other ancient references include a Babylonian tablet dated 567 BCE and a Chinese inscription dated 193 BCE.
What It Is
The spectacular light show of the northern lights is actually the result of a very violent reaction as energized particles from the sun slam into our atmosphere. The sun’s corona creates and ejects these charged particles, called the solar wind, which travel outward at more than a million miles per hour. As the solar wind approaches us, the Earth’s magnetic field attracts the particles towards both our north and south poles. As the solar wind smacks into the oxygen and nitrogen molecules in our atmosphere, those 1,000,000+ mph collisions produce tiny flashes of light. When there are billions of these collisions, the sky is filled with an undulating, dancing light show.
The intensity of the solar wind changes constantly. When the solar wind blows stronger, there is a more active and brighter aurora on earth, and it becomes visible further south. While a typical solar wind will produce a visible light show in the “auroral zone” north of 60°, which includes most of Alaska and northern Canada, a stronger wind will create northern lights that can be seen in parts of the continental United States.
As an example, a particularly powerful solar eruption occurred in March 1989, and made the northern lights visible as far south as Mexico. That same solar eruption created an electromagnetic field so strong that it briefly disrupted the entire electrical grid of the province of Quebec.
Colors
An unexplained mystery to me is related to the various colors of the auroras. The color most often seen is a vivid green, but it is not uncommon to see other colors as well - red or pink at the top, or blue and violet at the bottom of the displays. Most of the articles I’ve read agree that when the charged particles of the solar wind strike the various types of molecules that make up our atmosphere, the colors emitted are different. When an oxygen molecule is hit, for example, it will emit either a red or green color. When a nitrogen molecule is struck, it will emit a blue or purple color. What I was unable to find a satisfactory explanation for was why an oxygen molecule above about 180 miles altitude emits red, while oxygen molecules at lower altitudes, 60-180 miles high, give off a green color. Maybe one of my more knowledgeable friends reading this can enlighten me.
Southern Lights
The Aurora Australis is the name of the southern lights, and is just as common in the high southern latitudes as the Aurora Borealis is in the north. Both are caused by the same solar wind, and both vary similarly in intensity. It is, however, more difficult to observe the southern lights. Just as in the northern hemisphere, the auroral zone for the southern lights - where the southern display is most commonly seen, is below 60° south latitude, about where the Antarctic Peninsula begins. This means you’d have to travel to Antarctica in winter, which is not nearly as easy as flying into Anchorage or Fairbanks. During periods of strong solar winds, of course, the Aurora Australis can be seen much further north. It’s not uncommon to see it as far north as South Africa.
We spent several years sailing Nine of Cups in the far south, but never saw the southern lights while we were there. Just like in the north, the aurora is not visible in the summer, and we had no inclination to winter-over down in the far south, much preferring to sail back to the more temperate climes in winter. Plus, even Cape Horn, the furthest south we ventured, is only about 57° south.
Forecasts
Scientists have a limited ability to forecast the intensity of future auroras. By observing the solar surface and taking note of disturbances such as solar flares and sunspots, it’s possible to predict changes in the solar winds. Since it takes about three days for the solar wind to travel to earth, we know roughly what the auroral displays will be over the next three days. Also, since the sun rotates on its axis every 27 days, an area on the sun that caused an auroral display today might cause another display 27 days from now.
Finally, solar emissions are on an eleven year cycle. During the peak years, known as the solar maximum, there are huge solar storms that bombard the earth with extreme solar winds, causing the brightest and most frequent auroral displays, while in other years, the solar activity seems to lull. The last solar peak was in 2014; the next is expected in 2025.
Where and When to See
Although the intensity wanes and waxes hourly, the northern lights occur 24 hours a day, everyday, but to see them, you have to be in the right place at the right time. If you are watching anywhere within the auroral zone, i.e. north of 60° N, you should be able to view them on any clear, dark night, between September and April. It’s best to find a place outside the city where there’s not much ambient light. For some unknown reason, there is usually more activity around the equinoxes in September and March.
When the solar winds are stronger, the auroral displays are likely to be more dazzling, as well as viewable further south. The link here will take you to a three-day aurora forecast provided by the University of Alaska - Fairbanks’ Geophysical Institute. Below, I’ve copied their forecast for tonight. It’s a little tricky to figure out. The map in the center shows where the northern lights will be visible. Tonight, there will be a period of high activity, and the display should be viewable overhead as far south as Calgary and Winnepeg.
The bar graph on the right shows how intense the light show will be throughout the day. The kp scale ranges from zero to nine, where a zero would mean the display would be viewable only in the far north and quite dim, while a display with a kp of nine would be viewable throughout most of the U.S., and quite dazzling. According to the bar graph, tomorrow will see kp levels of five, quite high, between midnight and noon, September 3, UTC (Coordinated Universal Time). Since we are currently in the MDT time zone, which is 6 hours behind UTC, that translates to between 6 pm tonight, September 2, to 6 am tomorrow morning. Perfect!
The weather is calling for clear skies tonight, and the smoke from all the wildfires seem to be abating so we’re on our way to a remote campground far from the city lights. Now, if we can manage to stay up until 11 pm or so, we may be able to check off one of Marcie’s bucket list items.
We’ll keep you posted…