Photos don't do the northern lights justice.
To fully appreciate the glory and grandeur of this celestial display, which is also known as the aurora borealis, you have to settle beneath the ever-changing lights and watch them curve and curl, slither and flicker. [Amazing Auroras: Stunning Northern Lights Photos]
"I was camping, just lying out in a field in a sleeping bag on a late September night and looking up at the stars," said Terry Onsager, a physicist with the National Oceanic and Atmospheric Administration's Space Weather Prediction Center in Boulder, Colorado.
"All of a sudden, the most spectacular lights and swirls and rays just filled the sky, dancing and darting here and there," Onsager told Space.com. "It was just unbelievable."
Onsager had his aurora experience in northern Norway — one of the best places in the world to see the northern lights. You could follow in his footsteps, or blaze your own trail somewhere along the "auroral zone" that encircles Earth's northern reaches. But you need to know when and where to go. For example, the summer of 2018 may be a good time for a vacation, but a better time to see auroras is actually between winter and spring.
Read on to find out when and where to see the northern lights, and what powers this dazzling display.
When to go
If you're planning an aurora-viewing trip, make sure not to schedule it in the middle of summer. You need darkness to see the northern lights, and places in the auroral zone have precious little of it during the summer months.
You also want clear skies. Winter and springtime are generally less cloudy than autumn in and around the northern auroral zone, so a trip between December and April makes sense, said Charles Deehr, a professor emeritus and aurora forecaster at the University of Alaska Fairbanks' Geophysical Institute. Ideally, time your trip to coincide with the new moon, and make sure to get away from city lights when it's time to look up, he added.
"Dress warmly, plan to watch the sky between 10 p.m. and 2 a.m. local time, although an active period can occur anytime during the dark hours," Deehr wrote in the Geophysical Institute's guide to aurora viewing, which has lots of great information. "Active periods are typically about 30 minutes long, and occur every two hours, if the activity is high. The aurora is a sporadic phenomenon, occurring randomly for short periods or perhaps not at all."
You can get an idea of how active the northern lights are likely to be in your area by keeping tabs on a short-term aurora forecast, such as the one provided by the Geophysical Institute here: http://www.gi.alaska.edu/AuroraForecast
And you can have an aurora experience without even leaving your house if you so choose. The Canadian Space Agency offers a live feed of the skies above Yellowknife, in Canada's Northwest Territories: http://www.asc-csa.gc.ca/eng/astronomy/auroramax/.
Where to go in Europe
So where should you go? If you live in Europe, the easiest thing to do is head to the far northern parts of Norway, Sweden and Finland.
"In general, Scandinavia is set up," Deehr told Space.com. "They're in good shape for this."
Northern Norway, especially the area around Tromso, is a particularly popular destination, he added.
"There are a lot of tours, and a lot of English-speaking people who are willing to take you out," Deehr said, adding that the scenery in the region is "fantastic."
Or you could check out a number of other locations, such as northern Sweden's Abisko National Park.
"Abisko has developed a reputation for being the No. 1 aurora-watching destination on the planet, due to the fact that it is located in a very special microclimate with less precipitation than any other location on Earth that is located within the aurora zone," photographer Chad Blakley told Space.com via email. (The company Blakley co-founded, Lights Over Lapland, has been offering aurora tours in Abisko since 2010. In 2018, the company released footage from a spectacular all-sky aurora during a geomagnetic storm March 14.)
Iceland is also a good choice, Deehr said, as long as you make sure to set aside enough time to compensate for cloudy skies. (The island nation's weather can be uncooperative.)
Russia, by contrast, "is pretty much out," Deehr said. While a decent swathe of the auroral zone lies in northern Russia, such areas are relatively hard to get to and lack the tourism infrastructure most travelers are after, he explained.
Where to go in North America
There are also plenty of options for good aurora viewing in North America. But you should probably steer clear of far eastern Canada, which tends to be quite cloudy, Deehr said.
"Between James Bay and the west coast of Alaska — anywhere along that auroral zone is a good place to be," he said. (James Bay is the far southern portion of Canada's huge Hudson Bay.)
For example, he said, a northern lights trip could center on Yellowknife or Whitehorse, in the Canadian Yukon.
Or a traveler could take a train across the auroral zone to the town of Churchill, on the western shore of Hudson Bay — an area famous for its polar bear population.
"It's great, adventurous country," Deehr said of the Canadian auroral region.
In Alaska, anywhere from Fairbanks north offers good viewing. In Fairbanks itself, residents see the northern lights on about eight of every 10 nights, Deehr said.
The northern lights result when charged particles streaming from the sun collide with molecules high up in Earth's atmosphere, exciting these molecules and causing them to glow.
"It's like the fluorescent lights in our offices — they've got current running through them that excites the atoms, and the atoms glow," Onsager said.
The different colors of the northern lights come from different molecules: Oxygen emits yellow, green and red light, while nitrogen is responsible for blue and purplish-red hues.
Earth's magnetic field lines channel these solar particles toward the planet's north and south magnetic poles, which explains why auroras — the aurora borealis and its southern counterpart, the aurora australis — are high-latitude phenomena.
Indeed, the aurora borealis is visible most nights, weather permitting, within a band several hundred miles wide that's centered at about 66 degrees north — about the same latitude as the Arctic Circle.
This "standard" aurora is generated by the solar wind — the particles streaming constantly from the sun. But solar storms known as coronal mass ejections (CME) can ramp up the northern lights considerably and make them visible over much wider areas. Last year, for example, a CME allowed skywatchers as far south as Illinois and Ohio to get a glimpse. However, if you're planning an aurora-viewing trip weeks or months in advance, you can't count on any help from a solar storm and should therefore head to a destination somewhere near the northern ring. [The Sun's Wrath: Worst Solar Storms in History]
The southern auroral ring lies above Antarctica and is very difficult for skywatchers, or anyone else, to get to. That's why this article focuses on the northern lights — for reasons of practicality, not antipodean antipathy. (Southern Hemisphere dwellers take heart: The aurora australis can sometimes be viewed from New Zealand and Tasmania.)
There is also a mysterious, aurora-like brightening phenomenon in Earth's atmospher called "Steve" that isn't attributable to aurora, although scientists aren't sure of its cause.
Earth isn't unique in hosting auroras.
The huge gas giant planets (Jupiter, Saturn, Uranus and Neptune) each produce their own auroras due to their magnetic fields and thick atmospheres. However, the colors of the gases change because of differences in their atmospheres and magnetospheres.
Venus and Mars also have auroras, of a sort. The Venus Express spacecraft found solar field interactions with the planet's ionosphere forms a "magnetotail" that, when the accelerated particles hit the atmosphere, generates an aurora. Mars has local auroras over magnetic fields in its crust, as well as a larger, northern hemisphere aurora generated from solar energetic particles hitting the atmosphere.
Editor's note: If you capture an amazing photo of the northern lights and would like to share it with Space.com and our news partners for a story or gallery, send images in to at firstname.lastname@example.org.
This story, originally posted in April 2016, has been updated for 2019.