With the Sun’s activity increasing just a bit, sky watchers have witnessed an uptick in aurorae, especially northern observers. This top image is from an *extreme* northern observer, as in way up; about 320 km (220 miles) up above the Earth. Astronaut Doug Wheelock took this image from the International Space Station, and the beautiful sight made him wax poetic:
“Aurora Borealis as I will forever paint it in my dreams,” he wrote on Twitter. “Almost time to return home… no regrets… but mixed emotions. Leonardo da Vinci was right… ‘For once you have tasted flight, you will forever walk the Earth with your eyes turned skyward, for there you have been… and there you will long to return.'”
See other stunning recent aurora images from a more Earthly viewpoint:
Describing this picture, Salomonsen said on Flickr: “With a CME expected to hit earth on Nov.14th we could still see only a faint aurora. We got frustrated and then decided to drive back towards the city where it now was reported to clear up. After 5 minutes in the car suddenly we could see a strong aurora bursting out behind the partially cloudy sky.”
This is another gorgeous shot by Salomonsen, and on his Flickr site, he points out Ursa Major is visible in the top left, said it was just amazing how there were two rays of white and purple aurora, one moving faster than the other.
Photographer Sean Davies took this image on Nov. 13, 2010 near Dettah in the Northwest Territories, Canada, and said, “The aurora put on a great show just outside Yellowknife. The show lasted a good hour.” There’s another from Sean, below, on the same night. You can see more of Sean’s images at his Flickr site.
If you’ve even seen the Aurora Borealis live, you know how awe-inspiring it can be. But if you live too far south, or aren’t a night owl, there’s now a way for to you see the aurora, via the web, every night. Last night was the world premier of AuroraMAX – an online observatory which began streaming Canada’s northern lights live over the Internet. “Armchair skywatchers everywhere can now discover the wonder of the northern lights live on their home computer screen,” says Canadian Space Agency President Steve MacLean. “We hope that watching the dance of the northern lights will make you curious about the science of the sky and the relationship we have with our own star, the Sun.”
In addition to nightly broadcasts of the aurora, AuroraMAX will help demystify the science behind the phenomenon, offer tips for seeing and photographing auroras, and highlight Canadian research on the Sun-Earth relationship. The website will also include an image gallery with still photos and movies from previous nights.
Auroras occur as charged particles from the Sun collide with gases in Earth’s upper atmosphere. The launch of AuroraMAX coincides with the beginning of aurora season in northern Canada, which generally begins in late August or early September and ends in May. Aurora enthusiasts will be able to follow AuroraMAX through solar maximum, the most active period of the Sun’s 11-year cycle, which should produce more frequent and intense auroras on Earth. Solar maximum is currently expected in 2013.
AuroraMAX is a collaborative public engagement initiative between the CSA, the University of Calgary, the City of Yellowknife and Astronomy North.
For many people around the world the ability to see the Aurora Borealis or Aurora Australis is a rare treat. Unless you live north of 60° latitude (or south of -60°), or who have made the trip to tip of Chile or the Arctic Circle at least once in their lives, these fantastic light shows are something you’ve likely only read about or seen a video of.
But on occasion, the “northern” and “southern lights” have reached beyond the Arctic and Antarctic Circles and dazzled people with their stunning luminescence. But what exactly are they? To put it simply, auroras are natural light displays that take place in the night sky, particularly in the Polar Regions, and which are the result of interaction in the ionosphere between the sun’s rays and Earth’s magnetic field.
Basically, solar wind is periodically launched by the sun which contains clouds of plasma, charged particles that include electrons and positive ions. When they reach the Earth, they interact with the Earth’s magnetic field, which excites oxygen and nitrogen in the Earth’s upper atmosphere. During this process, ionized nitrogen atoms regain an electron, and oxygen and nitrogen atoms return from an excited state to ground state.
Excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule. Different gases produce different colors of light – light emissions coming from oxygen atoms as they interact with solar radiation appear green or brownish-red, while the interaction of nitrogen atoms cause light to be emitted that appears blue or red.
This dancing display of colors is what gives the Aurora its renowned beauty and sense of mystery. In northern latitudes, the effect is known as the Aurora Borealis, named after the Roman Goddess of the dawn (Aurora) and the Greek name for the north wind (Boreas). It was the French scientist Pierre Gassendi who gave them this name after first seeing them in 1621.
In the southern latitudes, it is known as Aurora Australis, Australis being the Latin word for “of the south”. Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red. The auroras are usually best seen in the Arctic and Antarctic because that is the location of the poles of the Earth’s magnetic field.
Names and Cultural Significance:
The northern lights have had a number of names throughout history and a great deal of significance to a number of cultures. The Cree call this phenomenon the “Dance of the Spirits”, believing that the effect signaled the return of their ancestors.
To the Inuit, it was believed that the spirits were those of animals. Some even believed that as the auroras danced closer to those who were watching them, that they would be enveloped and taken away to the heavens. In Europe, in the Middle Ages, the auroras were commonly believed to be a sign from God.
According to the Norwegian chronicle Konungs Skuggsjá (ca. 1230 CE), the first encounter of the norðrljós (Old Norse for “northern light”) amongst the Norsemen came from Vikings returning from Greenland. The chronicler gives three possible explanations for this phenomena, which included the ocean being surrounded by vast fires, that the sun flares reached around the world to its night side, or that the glaciers could store energy so that they eventually glowed a fluorescent color.
Auroras on Other Planets:
However, Earth is not the only planet in the Solar System that experiences this phenomena. They have been spotted on other Solar planets, and are most visible closer to the poles due to the longer periods of darkness and the magnetic field.
For example. the Hubble Space Telescope has observed auroras on both Jupiter and Saturn – both of which have magnetic fields much stronger than Earth’s and extensive radiation belts. Uranus and Neptune have also been observed to have auroras which, same as Earth, appear to be powered by solar wind.
Auroras also have been observed on the surfaces of Io, Europa, and Ganymede using the Hubble Space Telescope, not to mention Venus and Mars. Because Venus has no planetary magnetic field, Venusian auroras appear as bright and diffuse patches of varying shape and intensity, sometimes distributed across the full planetary disc.
An aurora was also detected on Mars on August 14th, 2004, by the SPICAM instrument aboard Mars Express. This aurora was located at Terra Cimmeria, in the region of 177° East, 52° South, and was estimated to be quite sizable – 30 km across and 8 km high (18.5 miles across and 5 miles high).
Though Mars has little magnetosphere to speak of, scientists determined that the region of the emissions corresponded to an area where the strongest magnetic field is localized on the planet. This they concluded by analyzing a map of crustal magnetic anomalies compiled with data from Mars Global Surveyor.
More recently, an aurora was observed on Mars by the MAVEN mission, which captured images of the event on March 17th, 2015, just a day after an aurora was observed here on Earth. Nicknamed Mars’ “Christmas lights”, they were observed across the planet’s mid-northern latitudes and (owing to the lack of oxygen and nitrogen in Mars’ atmosphere) were likely a faint glow compared to Earth’s more vibrant display.
In short, it seems that auroras are destined to happen wherever solar winds and magnetic fields coincide. But somehow, knowing this does not make them any less impressive, or diminish the power they have to inspire wonder and amazement in all those that behold them.
Scientists recently discovered something about auroras they never knew before. “Our jaws dropped when we saw the movies for the first time,” said Larry Lyons of the University of California-Los Angeles,(UCLA) describing how sometimes, vast curtains of aurora borealis collide, producing spectacular outbursts of light. “These outbursts are telling us something very fundamental about the nature of auroras.” These collisions can be so large, that isolated observers on Earth — with limited fields of view — have never noticed them before. It took a network of sensitive cameras spread across thousands of miles to get the big picture.
This network of 20 cameras, set up by NASA and the Canadian Space Agency was deployed around the Arctic in support of the THEMIS mission, the “Time History of Events and Macroscale Interactions during Substorms.” THEMIS consists of five identical probes launched in 2006 to solve a long-standing mystery: Why do auroras occasionally erupt in an explosion of light called a substorm?
The cameras would photograph auroras from below while the spacecraft sampled charged particles and electromagnetic fields from above. Together, the on-ground cameras and spacecraft would see the action from both sides and be able to piece together cause and effect—or so researchers hoped. It seems to have worked.
The breakthrough came earlier this year when UCLA researcher Toshi Nishimura assembled continent-wide movies from the individual ASI cameras. “It can be a little tricky,” Nishimura said. “Each camera has its own local weather and lighting conditions, and the auroras are different distances from each camera. I’ve got to account for these factors for six or more cameras simultaneously to make a coherent, large-scale movie.”
The first movie he showed Lyons was a pair of auroras crashing together in Dec. 2007. “It was like nothing I had seen before,” Lyons recalled. “Over the next several days, we surveyed more events. Our excitement mounted as we became convinced that the collisions were happening over and over.”
The explosions of light, they believe, are a sign of something dramatic happening in the space around Earth—specifically, in Earth’s “plasma tail.” Millions of kilometers long and pointed away from the sun, the plasma tail is made of charged particles captured mainly from the solar wind. Sometimes called the “plasma sheet,” the tail is held together by Earth’s magnetic field.
The same magnetic field that holds the tail together also connects it to Earth’s polar regions. Because of this connection, watching the dance of Northern Lights can reveal much about what’s happening in the plasma tail.
THEMIS project scientist Dave Sibeck of NASA’s Goddard Space Flight Center, Greenbelt, Md. said, “By putting together data from ground-based cameras, ground-based radar, and the THEMIS spacecraft, we now have a nearly complete picture of what causes explosive auroral substorms,”
Lyons and Nishimura have identified a common sequence of events. It begins with a broad curtain of slow-moving auroras and a smaller knot of fast-moving auroras, initially far apart. The slow curtain quietly hangs in place, almost immobile, when the speedy knot rushes in from the north. The auroras collide and an eruption of light ensues.
How does this sequence connect to events in the plasma tail? Lyons believes the fast-moving knot is associated with a stream of relatively lightweight plasma jetting through the tail. The stream gets started in the outer regions of the plasma tail and moves rapidly inward toward Earth. The fast knot of auroras moves in synch with this stream.
Meanwhile, the broad curtain of auroras is connected to the stationary inner boundary of the plasma tail and fueled by plasma instabilities there. When the lightweight stream reaches the inner boundary of the plasma tail, there is an eruption of plasma waves and instabilities. This collision of plasma is mirrored by a collision of auroras over the poles.
Movies of the phenomenon were unveiled at the Fall Meeting of the American Geophysical Union today in San Francisco.