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THE
SUN IS SHOWING ITS SPOTS
by Frank Snively (AVAS Co-President) - 10/29/03
Article About the October 2003 Solar Activity
CLICK PHOTOS
TO ZOOM
The photograph above was taken by Frank Snively on October
29. It was taken through a ND5 (100,000:1) sun filter mounted
on an 8 inch Celestron Shmidt-Cassegrain telescope, using ‘generic’
ASA 200 color print film. The exposure was 1/250 second. The
orange tint is induced by the filter, and not because the picture
was taken through the smoke of the recent fires.
Note from the editor: The photograph above was taken
from the SOHO
spacecraft Solar Observatory at about the same time
as Frank's photo. While the contrast may be a little better,
how close the 2 photos are goes to show you how much you can
really see with today's amatuer scopes and a standard camera.
- JMB |
Television news
and wire service newspaper press stories have mentioned that “solar
storms” have been taking place during the past few weeks. Such
“storms” are really clouds of high speed protons emitted
in solar flares, and are associated with sunspot activity. When
a large enough cloud hits the earth, there are aurora lights in
the night sky, communication disruptions, and possible power outages.
It is possible
to get a glimpse of the sunspots associated with the major storms
through welder’s goggles. To get a really good look requires
back yard observing equipment, such as was used to obtain the photograph
accompanying this article. Note that there are two major sun spot
areas, one showing a rather solid spot, while the other consists
of a “blotch” of numerous spots. The recent solar storms
are associated primarily with the irregular “blotch”.
There are also a number of very small (relatively speaking) spots
as well; these are not printing defects!
By our familiar
scales of distance, all the spots are huge. On the picture, the
“map scale” is approximately one inch = 300,000 miles.
The diameter of the Earth is 8000 miles, and an object of that size
would show as a speck less than 1/40 inch across on the picture.
One would hardly notice a feature the size of the earth!
What makes a
sun spot? First, note that appearances are deceiving. The “dark”
areas of the spots are bright , but they are indeed cooler and darker
than the surrounding material making up the surface of the sun.
The basic mechanism is that hot gases rising from the interior of
the sun are deflected away from some areas. The remaining material,
which is no longer heated from below to the same extent, radiates
into space and cools off. The deflection is caused by magnetic fields
coming up from the interior of the sun. The dark area is a “North”
or a “South” magnetic pole.(1)
In a “blotchy” area, there are both kinds of poles in
close proximity, which are moving about, attracting and repelling
each other. The associated magnetic field lines loop and twist and
snap. This field motion accelerates the ionized gases which make
up the sun, and expels some of them into space, making solar storms.
The intense magnetic
fields which produce the spots spread and weaken over time, so the
number and size of the sunspots changes. But the irregular motion
makes new spots as well. The rising motion of the hot gases also
collects and concentrates magnetic field lines, generating new spots.(2)
The whole process of magnetic field concentration and relaxation
over the entire sun passes through a somewhat irregular cycle having
a period of about 22 years.
Unlike the Earth,
where the “north” and “south” magnetic poles
remain relatively fixed, the magnetic polarity of the sun actually
reverses during a complete sunspot cycle. Start looking when there
are few or no spots. Gradually, the number of sunspots increases.
Those on one hemisphere have predominately “north” polarity.
The numbers then decrease over time, and commence to increase again.
In the subsequent maximum, the hemisphere we were looking at has
“south” polarity. Once again, the numbers decrease and
then increase, and at the end of the full 22 year cycle, we are
back to having “north” polarity on the original hemisphere.(3)
The present sunspot
cycle is indeed irregular. The nominal maximum of the most recent
cycle happened 2 or 3 years ago. Yet, here come a group of large
- and readily photographable - spots when overall solar activity
is supposed to be declining. It’s somewhat reminiscent of the
wet and dry patterns of our weather, only on a much larger scale.
Incidentally,
while there appears to be some connection between sunspot activity
and weather patterns here on Earth, the connection isn’t immediate.
It’s anybody’s guess whether the present sunspots will
cause us to get more or less snow this winter; the Denver Water
Board’s cloud seeding activities are likely to have greater
impact.
Some footnotes: To be sure, footnotes
aren’t customary in a newspaper article, but long standing
scientific training has “brainwashed” the writer.
(1) The fact
that sunspots have a definite magnetic polarity (either north or
south) was discovered by Prof. Horace Babcock at Caltech. He used
the spectroheliograph on Mount Wilson, near Pasadena, which he modified
to measure the circular polarization of some lines in the solar
spectrum.
(2) This
mechanism was first proposed and worked out in some detail by Prof.
Robert Leighton, an instructor of mine at Caltech, about 45 years
ago. This “Leighton random walk” model is generally accepted
as the basic mechanism for sunspot growth and propagation, but it
left some questions unanswered.
(3) I can’t
help but point out that about a year ago, I asked an astrophysicist
at U. of Colorado, who had just published a paper on solar atmosphere
and sun spot formation, about the mechanism for the overall polarity
reversal. I assumed that after 45 years, there might have been some
progress in understanding the phenomenon. However, I received no
answer. An astronomer at New Mexico State, who is the director of
the observatory which is used by U. of Colorado, said he didn’t
know why; at least he admitted it.
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