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The Apr 22 Lyrid Meteor Shower, Aurora Borealis and "STEVE"
April 4 and the 22nd had some excellent Aurora Borealis, and Saturday the 22nd was also the Lyrid meteor shower. The skies were clear for a brief time, so I saw a few Lyrid meteors.
Jerry Mason's photo above shows green auroral glow and blue streaks. Taken from College Way above Vernon at 10:30pm. I suspect the curved streak at right is a lens reflection from the streetlight at lower left.
Something new, have you heard about auroral proton arcs actually being a new high velocity 300km high, high temperature gas stream called "STEVE" acronym: Strong Thermal Emission Velocity Enhancement?
STEVE was assumed by aurora photographers to be a "proton arc". (Protons can hit the upper atmospheric gases also and while the electrons they bump loose can cause a glowing light, it's a broad, diffuse and dim glow unlike the structure of STEVE that is a narrow streamer with rotation and other motion.
Photo Credit: Karina & Amir, Vanexus Photography, Vancouver BC. Taken at Porteau Cove provincial Park in August 2016. "While it started as a thin white line, it transformed into vibrant greens and purples before fading away."
Basics about STEVE, from NASA's Aurorasaurus blog: source: http://blog.aurorasaurus.org/?p=449
1.STEVE appears ~10-20° (in latitude) closer to the equator (south in the Northern hemisphere) than where the normal green aurora is overhead. This means it could be overhead at latitudes similar to Calgary, Canada.
2.STEVE is a very narrow arc aligned East-West and extending for hundreds or thousands of miles.
3.STEVE emits light in mostly purplish colors. It is quite faint but is usually photographed with 5-10 second exposures.
4.Sometimes, it is accompanied by a rapidly evolving green short-lived picket fence structure.
5.STEVE can last 20 minutes or even longer.
6.STEVE appears to have a season. For instance, it has not been observed by citizen scientists from October 2016 to February 2017.
7.This phenomena has been reported from the UK, Canada, Alaska, northern US states, and even New Zealand.
"Ordinary auroras we see from the ground and space are caused by electrons precipitating down into the atmosphere," Dennis Gallagher of the Nasa Marshall Space Flight Centre said last year. "Protons can cause auroras, too, but they are different. For one thing, proton auroras are brightest in the UV part of the spectrum, invisible to the human eye."
There is some visible light from proton auroras, but these are broad and spread out, not tight and filamentary like the streaks seen in the photographs.
Eric Donovan, a professor of Physics and Astronomy from the University of Calgary:
With data gathered by Alberta's network of aurora watchers, Eric Donovan found it coincided with a flyby from one of the three satellites from the European Space Agency's Swarm magnetic field mission.
"As the satellite flew straight through Steve, data from the electric field instrument showed very clear changes. The temperature 300 km above Earth's surface jumped by 3000°C and the data revealed a 25 km-wide ribbon of gas flowing westwards at about 6 km/s compared to a speed of about 10 m/s either side of the ribbon," explained U of C astronomer Eric Donovan in an ESA blog post.
"It turns out that STEVE is actually remarkably common, but we hadn't noticed it before. It's thanks to ground-based observations, satellites, today's explosion of access to data and an army of citizen scientists joining forces to document it.
"Swarm allows us to measure it and I'm sure will continue to help resolve some unanswered questions."
Roger Haagmans, Swarm’s mission scientist added that there is still a lot we need to learn about Steve. For example, it is not created by the interaction of solar particles with the Earth's magnetic field, meaning it is not classified as an Aurora and requires further investigation.
So, instead of an aurora caused by solar particles slamming into air molecules, this turned out to be a super-heated ribbon of gases, where the air molecules were emitting light simply due to the heat, like the filament of an incandescent light bulb.
According to NASA's Aurorasaurus blog, there were more than 50 observed sightings of Steve (which has since been hammered into the acronym Strong Thermal Emission Velocity Enhancement) last year and they're hoping to gather more data in 2017.