Interplanetary Shock Wave Sparks Electric-Blue Auroras

Surprising sight seen by airplane pilots and passengers on “red eye” flight

Last night, April 19-20, a shock wave in the solar wind hit Earth’s magnetic field, sparking a moderately strong G2-class geomagnetic storm and rare “electric blue” auroras seen from airplanes in flight over Canada. Northern Lights spilled across the Canadian border into a number of US states.

An interplanetary shock wave hit Earth’s magnetic field on April 19th around 23:50 UT. When the disturbance arrived, the density of solar wind flowing around our planet abruptly quadrupled and a crack opened in Earth’s magnetic field. The resulting G2-class geomagnetic storm sparked unusual “electric blue” auroras.

“I’ve been flying airplanes for 20 years and photographing aurora for 10 years, but I’ve never seen anything like this before,” reports pilot Matt Melnyk who photographed the display from 39,000 feet:

“Electric blue auroras!” he says.

“This was while on a red eye flight from Edmonton to Toronto around 4 am over northern Manitoba. Unbelievable sky. I was able to grab some hasty shots with a cell phone.”

Auroras are usually green–a sign of oxygen. Rare blue auroras are caused by nitrogen molecules. Energetic particles striking N2+ at the upper limits of Earth’s atmosphere can produce an azure glow during intense geomagnetic storms.

During the storm, Northern Lights spilled across the Canadian border into more than half-a-dozen northern-tier US states. “The auroras were so bright, they could be seen inside the city of Kalispell, Montana,” reports Philip Granrud, who took this picture from the street in front of his house:

“We could see auroras for most of the night [even through the glare of our urban lights],” he says.

Auroras were also sighted in the southern hemisphere with an outburst of exceptional beauty over Tasmania.

What is an interplanetary shock wave? It is a supersonic disturbance in the gaseous material of the solar wind. These waves are usually delivered by coronal mass ejections (CMEs). Indeed, this one might have been a minor CME that left the sun unrecognized earlier this week.

Alternately, it might have been an unusually sharp co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. They contain plasma density gradients and magnetic fields that often do a good job sparking auroras.

High latitude sky watchers should remain alert for auroras on April 20th as Earth’s magnetic field continues to reverberate from the impact. Free: Aurora Alerts

Via NASA’s SpaceWeather

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Ron Long
April 20, 2018 10:21 am

Great post for modern kids! But teacher, the Interplanetary Shock Wave ate my homework!

April 20, 2018 10:42 am

Absolutely beautiful, and a perfect ‘perk’ for why one might want to become a pilot. I’ve only seen green auroras, tinged with white, whilst living in Wisconsin years ago—but my father and brother were fortunate enough in the 1990’s to have witnessed a CME-induced aurora strong enough to produce every colour of the rainbow. Jealous!

Reply to  AZ1971
April 21, 2018 7:17 am

We were west of Madison on out way to the farm on a winter Friday night about 11 pm. That early 1990’s aurora was so intense and beautiful that I stopped the car, woke the kids, and we stood on the side of the road for about 30 minutes admiring it. Every color of the rainbow, it seemed.

Jake J
April 20, 2018 10:42 am

I live near the Columbia River in Washington State. Woke up at 4 a.m., and looked northward and thought it was dawn until I looked at the clock. No blue, though. Just a pale green, which was another tipoff that it wasn’t dawn.

April 20, 2018 11:10 am

Great post – thanks!
While living in Ft. McMurray, AB I went to a trade show where a professional photographer was displaying his wares featuring Northern Lights. Several showed bright, blood red, which I had never seen. I asked him what kind of a lens filter he used – he was offended because they were natural color. I was doubtful for about a year until one night driving back to FM the aurora were dominated by bright red. No camera…but I now have a couple of his photos gracing my walls. Every year 100s of tourists come to Ft. McMurray to view the aurora.

Pop Piasa
April 20, 2018 11:42 am

The interplanetary magnetic field is pointing south often during the equinoctial passage and peaked at -19 during the night. That can magnify the solar wind’s effects as well.

April 20, 2018 11:45 am

What the SIDC says about it:
The sunspot group which appeared from the behind of the East solar limb
yesterday got numbered as Catania sunspot group 78 (NOAA AR 2706). This
sunspot group was source of the all (low B-class), flaring activity during
last 24 hours. We expect that Catania sunspot group 78 might be the source
of the B-class flares and possibly also isolated C-class flare in the
following 24 hours.
There were no Earth directed CMEs observed since the last report and the
solar protons remain at the background level.
The in situ observations showed sudden increase of the interplanetary
magnetic field magnitude (IMF), solar wind speed, density and temperature
at about 23:19 UT yesterday evening. All this indicates arrival of the
shock wave, however presently it is still unclear if the shock wave will be
followed by the ICME or this is a shock in the solar wind related with the
expected arrival of the fast flow.
The shock wave was followed by gradual increase of the solar wind speed and
IMF. The fast solar wind (up to 515 km/s) and longer intervals of negative
values of the Bz component of the IMF (down to -19 nT), resulted in the
active to storm geomagnetic conditions reported this morning (local station
at Dourbes reported K=5 and NOAA reported Kp=6).
The solar wind speed is presently about 480 km/s and the IMF is about 14
nT. If the solar wind speed will continue to increase and the Bz component
will show longer intervals with negative values we can expect continuation
of the disturbed geomagnetic conditions in the coming hours.”

Stephen Cheesman
April 20, 2018 11:50 am

Matt Melnyk has some amazing videos posted on the internet.

April 20, 2018 12:41 pm

Observers from Denmark made thorough recordings of the auroras appearance during period of 200 years.
It is no surprise that the aurora annual count is closely correlated with the Sunspot cycles numbers. What is somewhat surprising is that such correlation is stronger during the odd than during the even cycles (top left). This is also confirmed by the spectral composition of the auroral data by appearance of a strong component at the twice sunspot cycles’ periodicity (bottom left). Even more striking oddity is that the Land and Land & Ocean temperatures have strong 2xSunspot cycle periodicity despite having no 11 year periodicity component (top right)
This would suggest that solar activity has significant input into the global temperatures natural variability.

Reply to  vukcevic
April 20, 2018 2:51 pm


Reply to  vukcevic
April 22, 2018 11:57 pm

What is somewhat surprising is that such correlation is stronger during the odd than during the even cycles (top left).
Not so [regardless of what ‘NASA’ claims]. Geomagnetic activity [and thus aurorae] is stronger from solar maximum to the next solar maximum [actually polar field reversals] for transitions from even to odd cycles, and weaker for the transition from odd to even cycles.

April 20, 2018 1:17 pm

Not to be confused with Grain destruction in shocks in the interstellar medium in which plasma ions actually collide.

April 20, 2018 1:21 pm

There was a major (approaching severe) geomagnetic storm reported earlier today

April 20, 2018 3:57 pm

I think those are LEDs.

April 20, 2018 4:28 pm

Starter explanation of why aurora are seen in the polar regions, and the various colors.

Shanghai Dan
April 20, 2018 4:51 pm

At first I was really excited about this story, but then I realized it did NOT read “Interplanetary Spock Wave…”

Kristi Silber
Reply to  Shanghai Dan
April 20, 2018 5:21 pm

Thanks, that was a good one. Gave me a belly laugh.

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