APOD: Mysterious Green Patches on the Sky (2013 Sep 30)

[johnm.terry]

It seems to appear about the time, and move along with, the incoming tide - perhaps it is reflection from light sources off the water modified by internal camera reflections?

[Peto]

Looks like airglow to me

[Dai Bread]

The green clouds move in first from the distance towards the camera and at the end these clouds"" are replaced by other clouds moving from R to L . From the angle betwenn these atmospheric movements I suspect that a warm front was approachiong and that the cloud directions reflact the wind shear in an approaching front. Very high clouds can be noctilulinescent= I suspect the video shows the upper edge of an advancing warm front.

[doc2006b]

It's not aroural or reflected light. It is a result of the gel filter changing temperature and therfore the wavelenght that is is filtering the light at.

I have seen similar odd effects in my own work and I usually throw them out as "contaminated"

[AstroPuff101]

I there is too much in green in the whole time lapse to even try and figure out at this moment the mysterious green light, without first identifying and explaining all the local green color that seems to change itself

[Dave Parkhurst]

I agree with the "aurora" assumption! Judging by its very movement it appears to be what is termed "patchy aurora" or "pulsating aurora" which is exactly how auroral displays act when the initial power output of a mag-storm begins to subside or just never gathered enough energy in the first place to become a full blown geomagnetic storm. This type of aurora is actually very common and will usually occur just before dawn at the edge of twilight. I have seen this type of aurora countless times across Alaska over 3o years out in the field at all times of night...but most often just before dawn appears. While archival data shows low mag activity for the time period of UT day - August 11th, the bump in the mag-field was most noticeable at lower latitudes. It really would not take much of an opening in the mag-field for this type of aurora to occur especially in the shorter summer nights of August in New Brunswick, Canada and even at latitude north 46 degrees.

Of course there is a small possibility that it is a "digital anomaly"...but probably not because it seemingly has nothing to do with the "tides" or "editing" for the anomaly would have shown itself more than once, covered more than just a portion of sky or would show throughout the video.

[copperjet]

It looks more like a green-tinged aurora than something from the ocean reflecting onto the clouds.
Were there any other sightings of aurora that night?
The cloud-cover is pretty high. How would bioluminescent light reach that high?
I suppose it could be airglow.

[Warhorse]

Seems to be looking about NE (based on sky motion) from a latitude of N46. Can Aurora Borealis be observed from so far South?

Auroras are easily visible that far south. I'm at about N45, and I see dozens every year.

[ToddInNB]

I strongly suspect that these are just normal clouds with the green colour arising as an artefact from the digital camera's sensor (likely adjusted for white balance approximating that of daylight film) attempting to record an image in an extremely low light situation. If you notice, the rock formation in the centre foreground is also green...

[Vulpine]

It looks like an aurora.

I'm going to agree due to the color and relative motion of the light. Unlikely to be background light due to motion relative to clouds coming in at the last few seconds of the clip.

Second guess would be extremely high altitude noctilucent clouds.

[Hypatia]

Aurora often look like that when they're weak or when a display is just starting up. Sometimes the wisps are white and look like cirrus clouds but move much too quickly and are ephemeral—at least this was my observation when I lived in Alaska by the sea over a 15 year period. As this video is time-lapse it makes the task of insight more difficult. It could also be a reflection off the water as I believe someone has already suggested, or any number of things, but a patchy aurora seems most likely to me, and the colour seems correct.

[Phil T]

Hi,
This is certainly a camera artefact. The green patches appear even on the large rock to the left throughout the movie. Firstly neither aurorae nor clouds occur at this altitude and secondly rocks this weathered don't reflect light.

[felipecarvalhobc]

I go with one of the theories mentioned above.
To me, it's clearly the light reflected by the uprising tide, hitting the camera from below and from a chromatic angle of some sort.
The green light "in the sky" starts a bit earlier too, also accompanied by the rising tide.
This idea also explain why no one else registered the event that night, or ever.

[TallMallard]

Aurora!

[tvwatcher9]

This is to let you know I check APOD every day. As to what the green is...looks like aurora to me.

[Han-Tzong Su]

I am no airglow or aurora expert. However, we do run airglow or aurora observations at times using a satellite payload. It seems that if airglow or aurora occur in sky for a given location, then they will not disappear in seconds.

I tend to agree that it seems to come in with the tide. Judging from the video, there are local lighting. The light may have been reflected from the in-rushing water surface into the top of the lens. The lighting was further reflected from the lens barrel onto the lower portion of the CCD thus overlapped with sky, creating the mysterious green glows.

[cvg726]

This definitely appears to be a diffuse aurora. I saw two similar ones as a child in the 1950's. It was in the US northeast in a rural area with little light pollution.

[Beyond]

This definitely appears to be a diffuse aurora. I saw two similar ones as a child in the 1950's. It was in the US northeast in a rural area with little light pollution.

Well, you have better eyes than the photographer then. He didn't see it at all while photographing it. That's why he was wondering what it was.
http://asterisk.apod.com/viewtopic.php?f=29&t=32027

[edytajj]

I agree with matthank, cvg726, tvwatcher9...- the green lights have the exact same hue as the northern lights, which we do see a lot of here in Edmonton in every section of the sky (including the southern side). The lights move and look like a diffuse aurora (and remember Han-Tzong Su this is a time-lapse video so the lights lasted considerably longer than seconds) . They certainly do not look like bioluminescence (wrong hue) which I am familiar with (a nightly show I get to admire from the marine station on Vancouver Island). So why reject the simplest explanation when it fits?

[Rod]

Note that there other other such artifacts in the video. At second 17 in the video, the rock on the left appears to "emit" bands of green as the sky moves by. Then, at second 18, a small, very faint, circular green patch occurs slightly left of top center.

This disappears about second 19, however it is the precursor to the phenomena under discussion at second 24, which is approximately an hour later. You can see the small patch appear at 24, and again you will see green apparently emitted from the rock to the left.

Obviously, the light is being reflected by the incoming tide; note the brightening of the rocks as the water comes in and reflects the floodlights. That does not prove a correlation to the coloring of the clouds. However, as the tide reaches a certain height (at second 29), the clouds are still there but their colors are more normal for a night shot. If you look closely at second 29, you can actually see the same cloud (between the center cluster of rocks in the ocean and the cliff to their immediate right) rapidly change color from green to normal.

This leads credence to the light reflected from the Parks lighting system (behind rock to left), which is obviously powerful from the way its reflection illuminates the foreground after :28. The coloration could be explained by the type of lighting and/or the reflective properties of the water. There is one frame in second 29 that shows green reflected at the top, with more "natural" coloration of the clouds as you look down and to the right.

I believe this refutes the aurora hypothesis and strengthens the reflected light (and, yes, reflected ground light can easily affect cloud coloration, sometimes observable only longer exposures).

That being said, I'm a Texan and have never personally seen any aurora at all, though it is definitely in my bucket list.

Rod

[ENGR101]

Definite patchy airglow (often referred to as nightglow ) after sunset. And obvious aurora towards the end of the time-lapse video. Both the green airglow and the green aurora originate from atomic oxygen emitting at 5577 Angstroms -- that is why they have the very same colouring...

The camera is quite sensitive, the evidence being the very rich Milky Way and the large number of stars visible at the start of the animation. One might also argue that the "orange" colouring could be hydroxyl OH nightglow, as it's colouring brightens towards the horizon. One can even see an airglow wave above the left of centre rock in the sky at 16 seconds, moving downwards to the horizon.

Nice touch at the end -- watch the tide come in reflecting the light source behind the big rock on the right !!!

[GlobalGrant]

I am literally appalled that a NASA scientist and his University Professor astonomy partner at this webiste are unable to identify the aurora borealis. Have they never seen the aurora borealis before? If not, why not?

2013 is an unusually strong year for the aurora borealis. While not common at that lattitude, it is certainly within the realm of possibility for the aurora to be the source of the green glow in the sky in this video. Why was this possibility not checked thoroughly before posting this video and asking such a foolish question?

Instead of making themselves the laughing stock of the astonomical field, these two should have consulted with a sixth-grader, or maybe they should have asked a colleague or two. If they did consult with their colleagues and were still unable to identify the green glow, then they and their colleagues all need a refresher couse on cellestial events. They could start by travelling to Yellowknife, NWT, Canada where the aurora is visible more often during the dark winter months than almost anywhere else in North America. In Yellowknife they even make an industry out of showing the aurora borealis to about 10,000 visiting Japanese tourists each winter.

If you venture north, bundle up! It is cold out there at that time of year. But if you listen carefully, you can actually hear the aurora borealis as it dances over your head. Common place for those of us who live 'north of 60'.

[submariner al]

I am confident in the following: Reflected light off the tide front created by the lamp behind the front rock, which also illuminates the unobserved face of the wall behind which the camera sits. This unobserved face illuminates by reflection, the rock whence the light sits behind, at the same time as the tide comes in and the green washed light hits the camera.

Ta Da

[JohnCHeglin]

First, the film was taken in a region of the continent that I have never been to. It appears the film was taken facing south. This makes an aurora unlikely. It most resembles the descriptions of air glow, but I suspect otherwise. My guess is that it is a reflection of auroral light off of high clouds moving north. Whatever it is I look forward to the answer.

[powellite]

Most DEFINITELY Aurora. I'm surprised these are considered "mysterious"....

I have hundreds, if not thousands of similar time-lapse. Some of my time-lapse sequences shots show similar aurora "clouds" that pulsate too, not just fade in and out but pulsate wildly. In our Alaska winter, I typically run 3 digital cameras each night, 15-20 second exposure time resulting in about 3,000 high resolution pictures each night. Lots of strange, unearthly and beautiful aurora activity. Many of these subtle aurora "clouds" can be seen by the camera lens but not the human eye.

Dan (Fairbanks Alaska)