Atlanta tri-weekly journal. [volume] (Atlanta, Ga.) 1920-19??, 1923-06-02
BY ISABEL M. LEVI
cot the United States Naval Observatory
(Science Service.)

~ LID SOL is taking it easy these days and
l is in a remarkably Quiescent state for
- he is passing through the minimum
sunspot period. Sun spots those solar cyclones
that occasionally cause so much havoc with
telegraphic and radio communications upon
our own planet through the magnetic storms
that they produce in our atmosphere, are now
rarely visible on the solar surface. few
sporadic spots appear now and then but they
are insignificant, generally, and rapidly fade
away
According to the observations of DR.. G. H.
Peters of the United States Naval Observa-
tory, who photographs the surface of the sun
on every clear day and allows no sunspot,
however small, to escape his eye, the sun is
now very close to the sunspot minimum period
which occurs, on the average, once in eleven
years.
| 1t will not be possible to tell exactly when
the minimum takes place until later in the
| year when an examination of the continuous
| series of observations will show exactly
when the solar activity was at minimum.
The sunspot maximum occurred in the lat
ter part of 1917 and it has been expected that
the minimum would occur at some time dur
ing the present year. When the sun is pass
ing through the sunspot maximum period its
activity is greatest. There is then scarcely a
day that spots, singly or in groups, may not
be seen upon its surface. The faculae, or
cloudlike masses of intensely hot calcium va
por that occur most abundantly in the sun
|
that period. During the sunspot minimum
period, the faculae are at their minimum
brightness and sunspots may not appear on
the face of the sun for days at time.
| Strange as 1t may seem, the average annual
| surface temperature of the earth has been
found to be about degree lower at the time
| of sunspot maximum, when the sun is most ac-
| tive, than it is at the time of sunspOt mini
mum when the sun is most quiescent. The eX-
PLANTATION generally given for this state of at
fairs is that the atmosphere of the sun is
more dense during the period of maximum
solar activity and more permeated with the
Yapors of many elements that are being eX-
PEELED with great violence from the lower
strata owing to the marked increase in solar
energy. This increased density of the solar
atmosphere has screening effect upon the
solar radiations and there is consequently a
| slight decrease in the intensity of the radia-
lions that reach the earth's surface. The sun
has been found to be variable star, however,
with periods of short, irregular variations in
| the intensity of its radiations lasting a few
| days. weeks or months, as The case may be, in
addition to the longer period of variation
that is colnc1dent with the sunspot cycle. The
effect OF such short period variation may be
to mask or counterfeit, temporarily the eff
feet of the changes in the intensity of solar
radiation that attend the sunspot cycle. So,
while, in general, we may expect a higher
mean temperature for the earth during the
sunspot minimum period there may be a
spot-per1od solar variation superimposed
shat will temporarily mask this effect for a
few weeks or months.
1t IS also an interesting fact that in recent