a blue flash is better than a green flash

Walter Nissen (dk058@cleveland.Freenet.Edu)
Tue, 10 Aug 1999 08:53:36 -0400 (EDT)

There is no such thing as a unitary, or uniform, "green flash" phenomenon, 
such as you may have read about in less authoritative sources.  Let us 
stick to what we know.  The atmosphere separates photospheric light like a 
prism does.  Thus, the violet sun rises first and the red sun last.  At 
sunset the opposite is true, the red sun setting first and the violet sun 
last.  Thus, in its first moments at sunrise and its last moments at 
sunset, the color of the Sun will tend to vary (from its color when all of 
the "colored suns" are seen simultaneously, as is the case nearly all 
day).  Superimposed on these color changes is the color change from the 
long path taken simultaneously through the atmosphere.  This long path 
tends to scatter blue light more efficiently (thus the blue color of the 
midday sky) making the image of the Sun, which is formed only from light 
which survives the trip, redder in color.  In particular, violet and blue 
are frequently seen to be missing altogether.  The long path also quite 
commonly facilitates a wide variety of meteorological modifications of the 
My observations reveal a wide range of phenomena which seem well-explained 
by these basic principles.  In particular, the green flash is not 
something you either see or don't see, like some sort of step-function.  I 
have seen the classically described phenomenon, an extremely bright flash 
of green light, as "bright as flashbulbs".  Much more frequently, I have 
seen a bright green glow, lasting a greater or lesser length of time, and 
assuming a variety of shapes and sizes.  More frequently than that, I have 
seen merely bright green specks, also of various durations and sizes.  The 
large number of these specks I have seen may be inflated by the 
preponderance of my observations over a land horizon at sunrise through 
binoculars, where it is easy to catch a "first bit" through leaves of 
trees.  Many, many times, there is no green, not really, just yellow, or 
orange or red; many of these, of every hue.  I generally ignore any dim 
phenomena at sunrise, since I can't distinguish them from isolated 
illuminated clouds.  And it is only with experience that I can properly 
anticipate the pace of events at sunset and make this distinction then. 
On extreme occasions, the phenomenon is not green, but blue.  I have seen 
a number of bluish-green and greenish-blue phenomena, of various hues, 
mostly very green.  At the equinoctial sunrise, 1998 SEP 23, I saw a 
BRIGHT BLUE FLASH.  In detail:  The Sun rose behind trees, which are far 
away and not of any great consequence.  Immediately prior to sunrise, the 
whole area of the sky near the orient was especially luminous, so much so 
that it raised the question "Why is the sky already so bright if the Sun 
isn't up yet?".  I saw a definite brightening of the pale orange at the 
orient.  31.40 seconds after that, at 11h 18m 23.6s UTC (I was too excited 
to have the patience to obtain the hundredths, personal equation = about 
.25s not applied), I saw the "first bit"; it was bright green, rapidly 
evolving, giving way to green and yellow spreading out horizontally, and 
then it happened.  A BRIGHT BLUE FLASH, as blue as could be, not more 
green than violet, occurred 6.26s after the "first bit" and high, not 
directly in front of the first bit; but a fraction of a degree higher, and 
seemingly big, perhaps as big as the, as yet unrevealed, Sun.  After the 
blue flash, the color continued to evolve, moving left and right, until 
the green ended 3.24s after the blue flash. 
I spoke with an experienced and enthusiastic meteorologist, Andre Bernier, 
who said there was nothing very unusual about the weather at sunrise.  He 
said there was a small inversion of 10 or 15 degrees F for about 200 feet 
or 1000 feet at the surface.  Apparently, the key to seeing blue phenomena 
is a clear path, which can occur even if there are a few clouds as there 
As with my 9 observations of the corona of our Sun from within the umbral 
shadow of the Moon, but to a lesser degree, the words above are rather 
definitely insufficient to thoroughly describe the phenomena.  There is 
something very significant missing.  You have to be there and see them 
yourself to really understand.  (And this remains certainly true even if 
right now you are smugly telling yourself I am surely mistaken in this. 
It's an observing thing). 
Walter Nissen                   dk058@cleveland.freenet.edu 
-81.8637, 41.3735, 256m elevation 
This sky observing report is pretty far off-topic.  But I know from direct 
correspondence with a number of you that you would like to hear this from 
me.  So long as no one without such special knowledge emulates this 
excursion, we should be ok.  Please note, especially, that the purpose of 
this message is to share desired information, and not, e.g., for some 
selfish purpose.  Even saying that, I apologize to those more focused on