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From: rpw3@redwood.UUCP (Rob Warnock)
Newsgroups: net.physics
Subject: Re: Sunrise Phenomenon
Message-ID: <71@redwood.UUCP>
Date: Fri, 2-Nov-84 06:55:35 EST
Article-I.D.: redwood.71
Posted: Fri Nov  2 06:55:35 1984
Date-Received: Sat, 3-Nov-84 22:26:46 EST
References: <1345@drutx.UUCP>
Organization: Rob Warnock, Redwood City, CA
Lines: 50

+---------------
| 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)?
+---------------

I'll give it a go, though I don't know how accurate this is...

+---------------
| 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?
|     Paul Given             {ihnp4, houxe, stcvax!ihnp4}!drutx!pagiven
+---------------

I believe what you are seeing may be literally the shadows of the
contours of the Earth just below the eastern horizon. That is, there
will be places (below the horizon) which are lower than others, and
through those "gaps" sunlight will stream overhead (your head) before
the sun is completely above that "further horizon". (I'm not explaining
this very well, am I?) Since raw sunlight in such beams is very much
brighter than the general scatter of the false dawn, you will see these
shafts of light (due to scatter), much like a searchlight.

A similar phenomenon occurs towards the end of a total solar eclipse,
when the Sun begins to peek out from behind the Moon, producing what
is called the "wedding ring" (bright "hot spots" where sunlight is
actually shining through valleys or mountain passes at the horizon
of the Moon).

If is indeed seen more often in the morning, it is probably because the
air is more still then than at the corresponding time in the afternoon
(after the Sun has heated up the local earth and water and stirred up
all sorts of thermals and currents), and the still air allows a clearer
definition of the "rosy fingers".

[ O.k., I've stuck my neck out... anybody want to chop it off? ;-} ]

Rob Warnock

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