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From: jlg@lanl.ARPA
Newsgroups: net.physics
Subject: Re: Sunrise Phenomenon
Message-ID: <15524@lanl.ARPA>
Date: Fri, 2-Nov-84 15:03:21 EST
Article-I.D.: lanl.15524
Posted: Fri Nov  2 15:03:21 1984
Date-Received: Sat, 3-Nov-84 21:55:03 EST
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Organization: Los Alamos National Laboratory
Lines: 36

> 
>                                  -
> Can anyone out there explain the atmospheric  phenomenon  known  as
> the  "rosy  fingers  of dawn" in reasonably plain English (that is,
> without invoking quantum chromodynamics or other esoteric  theory)?
> In  case this beautiful morning sight is known by another name, let
> me explain: On a cloudless morning, just before the limb of the sun
> breaks the horizon, deep pink shafts of light radiate from the hor-
> izon to just beyond directly overhead but not quite to the  western
> horizon.   There  appears  to  be four or five very sharply defined
> shafts of light, alternating with deep blue, growing with intensity
> as  the  horizon  is  neared.   One is reminded of the "rising sun"
> Japanese flag symbol.  Interestingly enough, I have never seen this
> at sunset.  Can it happen then, too?

I have seen this a number of times at both sunrise and sunset.  On one
very dramatic occasion the cause of the phenomon was also directly in 
view.  It was a distant mountain who's contours cast a shadow on the 
lower atmosphere.  In the places where the mountain was lower, the 
sunlight reaches lower into the air above me, and a brighter shaft of 
light was produced.  

I don't know if this is the only cause of the phenomon, but it is certainly
A cause.  Try looking around for large obsticles on the horizon and
position yourself so that it is between you and the setting (or rising)
sun.  You should be a sufficient distance away for the object to cast
shadows on you only when the sun is at or below horizontal.  Your best
chance is on a day with thermal inversion layers in the atmosphere so
that the difference in scattering between one atmospheric level and
the next is most apparent.  (This may be why you have only seen the
effect at sunrise.  Inversion layers form over cities at night, but are
usually burned off by the sun during the day.  Only in regions with
shallow valleys bordered by mountains do inversion layers form during
the day.) 

Good hunting!