Home - Intro - Compare - Differ. Refraction - Discussion - Polarization - Terminator - Moon - Definitions - Cold vs Warm

Double Sunset - Data - Sunset Sequence - Homage - Sunrise - Last Line - Global Warming - Archives





POLARIZATION OF TWILIGHT



[F152205u.jpg]

Video capture of anti-solar region, despite –3 degrees sun brightness is quite strong. Weather is –40 on the surface. The dark figure on bottom left is my finger about to rotate Polaroid lens.

[F152205p.jpg]

Video capture a few seconds after with Polaroid lens rotated. The picture shows greater polarization above the anti-solar horizon. Suggesting horizontal Polarization.



[NOAAVISUAL]

Satellite picture taken 55 minutes before, showing no light over Resolute. “ Is there light or no light?” that is the question.
Is Polarization playing a role in the apparent darkness captured by a Satellite almost directly above?



An excellent rediscovery.

It is very humbling and thrilling to admit that there is Polarization of twilight in the Arctic only after living in it for nearly 20 years without ever shedding one thought about it. A look back of striking images of polar memories makes it so obvious, yes its polarized, and yes this is partly why twilight light is so dramatically different then daylight. What is not so obvious, is that this fact has been known for quite sometime without much fuss about it. Hulburt, Rosenberg and others have done the pioneering work on this subject some 70 years ago. But their twilight lasted a few minutes, while ours lasts up to 10 hours! The difference is essentially that we in the High Arctic are seriously influenced by twilight, half the year is twilight, same goes with all animals who live up here. It is a bit of a shock to realize that we are mostly dwelling in polarized light near the Pole. Although Polarization has no basis for making the name “Pole”as in North Pole, the words are definitely intertwined in a real living sense, one can’t be without the other.

Then again comes ignorance, very well established, that there isn’t any Polarization to worry about in our world. Although a great chunk of the world is near the Poles. This education gap certainly is part of the great misconceptions associated with EH2r, no sunsets or sunrises can be calculated correctly during the cold season, no twilight can be estimated correctly during the same time period. It is also obvious, that there is a huge “light gap” in the equations of the polar regions. For instance, in the pictures below you will be able to see light when the sun is 10 degrees below the horizon. This light is most certainly Polarized, I hesitate, but estimate it to be mostly in the Horizontal plane. The technique to determine Polarization is very simple and well known, the rotation of a Polaroid lens darkens when placed opposite to the polarized light plane. There are significant issues associated with Polarized light, namely Polar Orbiting Weather Satellites, which appear to completely fail to perceive correctly the true amount of light carried over by refraction, this “light gap” is extremely significant, not small, it is in the order of 120 to 240 nautical miles. In essence present day Orbital Satellite programs, even the most modern ones, routinely cut off a huge segments of light, thus creating the paradox, not seeing light is believing, but in this case, meteorological satellites are made somewhat blind.

The ease by which polarization is measured is a bit misleading:

“The observed rotation of the plane of polarization from the direction given by the position of the sun cannot be explained simply by the assymmetry in the solar illumination and should be studied more closely in relation to the problem of fluorescent luminescence or other types of emission in the night sky.” Zdenek Sekera 1951

Determining true directions is a matter of deep study, beyond the scope of this paper, at least until I get better equipment. If it was purely a matter of rotating the polaroid lens, it would be easy, but it turns out that the apparent same rotation gives the same effect everywhere except near the sun azimuth., the twilight bright zone, usually coloured yellow,orange and red. All other sectors appear strongly polarized especially the purple anti-solar region, this leads me to tentatively conclude that Arctic twilight is polarized horizontally. Polarization during twilight appears from the earliest onset of light, although it is very difficult to note it visually. As the sun elevation increases, the bright zone expands and occupies a greater sector of the sky, but even at high sun elevations (-3 degrees) polarization is still present. Observing brighter than expected twilight again means that light is carried further by refraction, much more than at locations with warmer atmospheres.

I must very much thank, especially share all aspects of this rediscovery with Doctors Gunther Konnen, Andy and Siebren , they were as invaluable as are my own eyes. Their technical advice and historical knowledge inspired this work, although the views expressed are my own, as someone wrote “a novice “on this subject.

The following pictures are all taken in Resolute Bay: file names give the precise date, for instance j171912u.jpg means:

J = January 2002
17 = Day
1912 = Hour Universal Time or GMT.
U = Picture without filter.
P = Picture with Polaroid lens rotated until image is at its darkest.

Discovery dated Feb 10, 2002