Last Friday evening, May 10, our region (and indeed the entire U.S.) saw the finest display of the Northern Lights since 2001. Locally, the Ashokan reservoir was packed with observers. People posted images on Facebook and the phones kept ringing, urging friends to go out and look up.
Now is an ideal time to review what happened, examine our future prospects and tune into the epic realities of the aurora borealis. I was naturally asked to cover this since I’ve been this publication’s astronomy columnist since the mid-70’s. But more than that, I wrote a major book about this (The Sun’s Heartbeat, published by Little Brown) and also work for a science tour company that’s been bringing yearly aurora groups to the Arctic Circle after hanging out with researchers, since 1998. Happily, we’ve never failed to observe the mythical Lights. So I’m not going to regurgitate stuff published elsewhere: I’m here to help you see these magical displays without needing to travel.
Still, we shouldn’t pretend the same rules apply to observers here and those in the far North. Not only are the displays near-nightly occurrences up there, but they look much different from the ones we sometimes see. There are also some hard-and-fast realities: A camera always greatly accentuates colors so that a slightly-reddish glow seen overhead in the mid-Hudson region will, on your camera, produce an intense crimson not inferior to a traffic light.
This means that if you missed last Friday’s display, and drool disappointedly at the marvelous images posted to Facebook, be aware that that’s NOT what you missed. Had you been outdoors when the display peaked at around 10:30 p.m., you would not have seen the images seen in all those photos.
That’s because human color vision barely responds to low-light phenomena. When we do see dim objects, our retinas have a strong sensitivity and bias toward green, especially yellow-green, and a pronounced inability to observe faint reds. Since the aurora mostly creates green colors from glowing oxygen (at 557.7 nanometers wave length, if you’re a physics nerd like me) that’s the sky-color our groups have been enjoying all these years up in Alaska.
But oddly, very oddly, that’s not what happened last Friday. Long ago, University of Alaska aurora expert Dr. Neil Brown told our group that “a red aurora is a once-in-a-lifetime experience.” But red is the color that dominated last week. Even more strangely, that hue was even faintly visible to the naked eye! Photos of course greatly boosted and saturated it, making the sky seem colored with swatches of red paint.
Thus, last week, we not only saw a rare mid-Hudson aurora, but an even rarer red version! Okay, so it’s time to back up a bit.
The Sun always shoots off broken bits of atoms called the solar wind, and when it interacts with Earth’s magnetic field, it produces nearly permanent donut-like glows surrounding our magnetic poles. There’s rarely an aurora in the dark center of those rings, nor in areas well south of the northern version. But if you can get to a place that’s usually under that donut, you’ll see an aurora most nights, which is why we annually take people to our secret rural Alaskan places. (Some year please join us by checking out SpecialInterestTours.com ). But here’s the thing: When solar storms erupt with flares or even coronal mass ejections, the shotgun-like stream of charged solar particles greatly increases the wind’s density and speed. Then the auroras get far more intense, plus the donut expands to hover over places far to the south — sometimes even right above us, and, rarely, even over people in Mexico. That’s what happened last weekend.
This doesn’t often occur. After getting lovely auroras in the mid-‘70’s and early ‘80’s, our region saw an amazing overhead all-night aurora on March 13, 1989. Then not again until October of 2000. Then a year later in October, 2001. And then not again until this weekend. So it’s a rare treasure.
There were also other occasions whose dates I didn’t record when we had auroras that were either very short, meaning lasting for less than a half hour, or else happened above overcast skies or around the time of the Full Moon.
Which brings up the vital issue of what totally spoils our region’s rare auroral displays. Because the Northern Lights are usually faint, it’s subdued or totally hidden by city lights. Even by the downtown lights of small cities like Kingston and Newburgh. So you need to get out to the countryside.
A bright Moon can do just as much harm. So forget the Northern Lights during one-third of each month, during the ten-day period surrounding the Full Moon. Next up is weather. Naturally you want mostly clear conditions, but you also need an absence of haze or high thin clouds. The occasional cloud is okay, so let’s say “partly cloudy” or “mostly clear” is the forecast you want to hear for the upcoming night.
Now for the fine points, the ones that are less vital but are still need-to-know items. First, you want a wide-open swath of sky. Nature’s absolute-greatest spectacle, a total (never partial) solar eclipse, can be nicely seen through a gap between trees or clouds. But not the aurora. Its patterns’ sheer size requires a huge area of unblocked celestial real estate. Also be aware that while many major displays like the one we just saw can fill the whole sky and look fabulous directly overhead, most exhibitions concentrate less than halfway up the sky toward the northwest.
Not due north, where Earth’s rotation pole lies. Auroras surround our magnetic pole, and from here, that lies toward the northwest. Next is the issue of vision. You need your eyes to be dark-adapted, which requires that you patiently stay in darkness for at least 5-10 minutes. If you merely go out to your deck, look up and see nothing but some stars and then shrug and go back in, you may have blown it. The patterns and any colors require dark adaptation. Toward that end, be sure to extinguish any yard lights and even illumination from windows. If cars may be passing, don’t look at headlights even for a moment. Better still, get to a spot where streets or roads are blocked by an intervening building.
Finally, the issue of photography. Some celestial objects look best when viewed directly, like Saturn or the half-Moon through a telescope, or a total solar eclipse. Others are greatly enhanced by photography. For example, no galaxy has ever shown any color through any size telescope, while long-exposure images bring out details, campfire-yellow galactic centers, and a blue cast enveloping the intricate structures of its spiral arms. None of that is visible by direct observation. But the Northern Lights are a mixed bag. A camera, as we’ve seen, greatly boosts the colors and can enhance filamentary detail. Direct observing, by contrast, shows any active animation as well as large-scale patterns. All in all, then, both have their place when it comes to the fabulous mythical Lights.
As for the future, the Sun is now hitting the peak of solar cycle 25. Which means in the next two years there should be more solar storm activity and auroras than we’ll see again until 2035. It’s a great period for the Northern Lights. How to know exactly when they’re likely?
Go online to “aurora forecast,” which is put out and updated by the University of Alaska at Fairbanks. Then check the Moon’s phase to see if this is even a doable period with dark-enough skies. And, of course, check the weather. Moreover, a big coronal mass ejection isn’t enough. If you want to get serious about this, check out current solar images: You want the solar storm to be just to the right of the middle of the Sun’s disk. From that position, some 2-3 days’ worth of Sun-rotation after the storm has been dead center, it’s in the best position for the curvy solar magnetic field to carry that swarm of material — sometimes ten billion tons of it — to follow the so-called Parker Spiral to make a bulls-eye on our planet.
And then the fun begins.
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