isolated arc – The Amazing Sky

October 7, 2017

The Aurora Starring Steve

"Steve," the Strange Auroral Arc (Spherical Fish-Eye Projection)

I’ve assembled a music video of time-lapse clips and still images of the fine aurora of September 27, with Steve making a cameo appearance.

The indicators this night didn’t point to a particularly great display, but the sky really performed.

The Northern Lights started low across the north, in a very active classic arc. The display then quietened.

But as it did so, and as is his wont, the isolated arc that has become known as Steve appeared across the south in a sweeping arc. The Steve arc always defines the most southerly extent of the aurora.

Steve faded, but then the main display kicked up again and began to fill the sky with a post-sub-storm display of pulsing rays and curtains shooting up to the zenith. Only real-time video can really capture the scene as the eye sees it, but the fast time-lapses I shot do a decent job of recording the effect of whole patches of sky turning on and off.

The display ended with odd pulsing arcs in the south.

Here’s the video, available in 4K resolution.

Alberta Aurora (Sept. 27, 2017) from Alan Dyer on Vimeo.

Expand to fill the screen for the best view.

Thanks for looking!

May 12, 2017May 12, 2017

Meet Steve, the Odd Auroral Arc

Red Auroral Arc #1 (May 10, 2015)

Stargazers in western Canada will have seen him – Steve, the odd auroral arc.

There’s been a lot of publicity lately about an unusual form of aurora that appears as a stationary arc across the sky, isolated from the main aurora to the north. It usually just sits there – motionless, featureless, and colourless to the eye, though the camera can pick up magenta and green tints.

We often see these strange auroral arcs from western Canada.

In lieu of a better name, and lacking a good explanation as to their cause, these isolated arcs have become labelled simply as “Steve” by the aurora chasing community (the Alberta Aurora Chasers Facebook group) here in Alberta.

In a gathering of aurora chasers at Calgary’s Kilkenny Pub, aurora photographer extraordinaire and AAC Facebook group administrator Chris Ratzlaff suggested the name. It comes from the children’s movie Over the Hedge, where a character calls anything he doesn’t understand “Steve.” The name has stuck!

The 270° panorama from March 2, 2017 shows Steve to the west (right) and east (left) here, and well isolated from the main aurora to the north.

This is the view of that same March 2, 2017 arc looking straight up, showing Steve’s characteristic gradient from pink at top though white, then to subtle “picket-fence” fingers of green that are usually very short-lived.

The view above is Steve from exactly 6 months earlier, on September 2, 2016. Same features. I get the impression we’re looking up along a very tall but thin curtain.

Another view of the September 2, 2016 Steve shows his classic thin curtain and gradation of colours, here looking southeast.

Looking southwest on September 2, 2016, Steve takes on more rippled forms. But these are very transient. Indeed, Steve rarely lasts more than 30 minutes to an hour, and might get bright for only a few minutes. But even at his brightest, he usually looks white or grey to the eye, and moves very slowly.

Here’s a classic Steve, from October 1, 2006 – a white featureless arc even to the camera in this case.

So what is Steve?

He is often erroneously called a “proton arc,” but he isn’t. True auroral proton arcs are invisible to the eye and camera, emitting in wavelengths the eye cannot see. Proton auroras are also diffuse, not tightly confined like Steve.

Above is Steve from August 5, 2005, when he crashed the Saskatchewan Summer Star Party, appearing as a ghostly white band across the sky. But, again, the camera revealed his true colours.

Steve Auroras in 2015 from Alan Dyer on Vimeo.

Here are a couple of time-lapses from 2015 of the phenomenon, appearing as an isolated arc overhead in the sky far from the main auroral activity to the north. I shot these from my backyard in southern Alberta. In both clips the camera faces north, but takes in most of the sky with a fish-eye lens.

In the first video clip, note the east-to-west flow of structure, as in classic auroras. In the second clip, Steve is not so well-defined. Indeed, his usual magenta band appears only briefly for a minute or so. So I’m not sure this second clip does show the classic Steve arc.

The origin and nature of Steve are subjects of investigation, aided by “citizen science” contributors of photos and videos.

Local aurora researcher Dr. Eric Donovan from the University of Calgary has satellite data from the ESA Swarm mission to suggest Steve is made of intensely hot thermal currents, and not classic electrons raining down as in normal auroras. He has back-acronymed Steve to mean Strong Thermal Emission Velocity Enhancement.

Learning more about Steve will require a unique combination of professional and amateur astronomers working together.

Now that he has a name, Steve won’t be escaping our attention any longer. We’ll be looking for him!

March 4, 2017March 4, 2017

Auroras from Alberta

Aurora Self-Portrait (March 2 2017)

The solar winds blew some fine auroras our way this past week.

Oh, that I had been in the North last week, where the sky erupted with jaw-dropping displays. I could only watch those vicariously via webcams, such as the Explore.org Northern Lights Cam at the Churchill Northern Studies Centre.

But here in southern Alberta we were still treated to some fine displays across our northern sky. The image below is from March 1, from my rural backyard.

Fish-Eye Aurora (March 1, 2017) — A full-frame fish-eye lens image of the aurora on March 1 with curtains reaching up into the Big Dipper.

The Sun wasn’t particularly active and there were no coronal mass ejections per se. But a hole in the corona let a wind of solar particles through to buffet our magnetosphere, stirring up geomagnetic storms of Level 4 to 5 scale. That’s good enough to light our skies in western Canada.

Aurora over Frozen Pond — A 160° panorama of the main auroral oval to the north on March 2 about 11:40 pm MST.

Above is the display from March 2, taken over a frozen pond near home. I like how the Lights reflect in the ice.

This night, for about 30 minutes, an odd auroral form appeared that we see from time to time at our latitudes. A wider panorama shows this isolated arc well south of the main auroral oval and forming a thin arc stretching across the sky from west to east.

Aurora Panorama with Isolated Arc — A 220° panorama of the isolated arc to the west (left) and east (right) and the main auroral oval to the north.

The panorama above shows just the western and eastern portion of the arc. Overhead (image below) it looked like this briefly.

Isolated Auroral Arc Overhead — The overhead portion of the isolated arc at its peak.

Visually, it appeared colourless. But the camera picks up this isolated arc’s usual pink color, with a fringe of white and sometimes (here very briefly) a “picket-fence” effect of green rays.

Isolated Auroral Arc West — The western portion of the isolated auroral arc at its peak.

This is the view of the isolated arc to the west. Erroneously called “proton arcs,” these are not caused by incoming protons. Those produce a very diffuse, usually sub-visual glow. But the exact nature of these isolated arcs remains a mystery.

As we head into solar minimum in the nest few years, displays of Northern Lights at lower latitudes will become less frequent. But even without major solar activity, last week’s displays demonstrated we can still get good shows.

September 7, 2016September 7, 2016

Sweep of the Auroral Oval

Arc of the Northern Lights

The aurora has been lighting up our skies a lot in recent nights, in a great sweeping arc across the northern sky.

It’s been a good week or so for Northern Lights, with several nights in a row of fine displays. These images are from one night, taken near home in southern Alberta, on September 2.

The lead image at top shows the display at its best, with the arc of curtains reflected in a nearby pond. The green curtains fade to shades of magenta as they tower into the high atmosphere, as one process of glowing oxygen giving off green light transitions to another emitting red light.

Concentric Arcs of the Auroral Oval — A 180° panorama of the Northern Lights exhibiting classic concentric ars across the north, with an isolated arc to the east at far right. This is a stitch of 10 segments, each 2-second exposures with the 20mm Sigma Art lens at f/1.6 and Nikon D750 at ISO 3200. Stitched with PTGui.

A little later the curtains had changed form, into a more homogenous arc above a set of sharper curtains below that are farthest north. People in northern Alberta or the Northwest Territories would have been seeing these curtains dancing above them.

What we are seeing is the classic curving arc of the auroral oval, the ring of light created by electrons raining down into our atmosphere in roughly an oval sweeping across the continent and centred on the magnetic pole in the Canadian Arctic.

However, at right, you can see a odd detached bit of more southerly aurora, with a dominant red colour.

Isolated Auroral Arc #2 (Sept 2, 2016) — An isolated auroral arc to the east on September 2, 2016, shot from near home during a fine display with active curtains to the north at left. A single 8-second exposure with the 20mm lens at f/1.4 and Nikon D750 at ISO 3200.

This is a closeup, showing the characteristic form of these odd “isolated arcs” — usually featureless, often thin, without much motion, and often red.

Isolated Auroral Arc #4 (Sept 2, 2016) — An isolated auroral arc to the west on September 2, 2016, shot from home during a fine display with active curtains to the north. A single 13-second exposure with the 20mm lens at f/1.4 and Nikon D750 at ISO 3200.

Later, the arc had brightened and expanded to cross the sky. The above view is looking west from home, with the arc now displaying a mix of pink, white and green.

Isolated Auroral Arc #3 (Sept 2, 2016) — An isolated overhead auroral arc on September 2, 2016, shot from home during a fine display with active curtains to the north. The Summer Triangle stars stand out here due to high cloud fuzzing their images. A single 13-second exposure with the 20mm lens at f/1.4 and Nikon D750 at ISO 3200.

Here, we are looking up the isolated arc, with the impression of it being a thin sheet seen at an angle, with the bottom green component being closest and the red top being highest and farthest away.

Isolated Auroral Arc #5 (Sept 2, 2016) — An isolated auroral arc to the southeast on September 2, 2016, shot from home during a fine display with active curtains to the north. This one displays the classic picket fence apperarance, with fingers of green aurora that moved along the band during a time-lapse of the scene. A single 13-second exposure with the 20mm lens at f/1.4 and Nikon D750 at ISO 3200.

This is the view looking southeast to the strange aurora. For a time it broke up and displayed a “picket fence” formation. And it moved!

Just what these isolated arcs are is a mystery. They have been called “proton arcs,” under the assumption they are caused by incoming protons, not electrons. But while there are such things as proton arcs and auroras, they are diffuse and invisible to the eye and camera in normal visible light. So these features are not proton arcs.

Nevertheless, these odd arcs are not like the usual auroral curtains, and likely have a different origin. But just what is still the object of research. Images by amateur astronomers such as these can help in the study.