[HCARC] Maximum Sunspot Number - Monday night HCARC Net

[Kerry]

In response to question from Steve, WD5ENH, here are some solar data 
from 1957-58.  I haven't actually found the peak sunspot number for 
Cycle 19 which peaked in late 1957, however, I have some data.  The 
sunspot numbers are not easy to deal with as there are at least 3 
different sets of numbers.  These are the International or Zurich 
numbers which go back to 1749.  There are numbers from before 1749, 
however, these were estimated by Wolf and Fritz using various non-solar 
observations.   A year or so ago, these numbers were 'corrected' and 
have changed slightly. The second set of numbers are the the Boulder 
numbers.  These tend to be about 50% higher than the Zurich numbers.  
The third set are the AAVSO (American Association of Variable Star 
Observers) numbers.  The AAVSO numbers tend to be about 10% higher than 
the Zurich numbers.  The difference between the numbers is because of 
the way the actual observed numbers are 'adjusted' so they are 
comparable to the older numbers.  This is caused by the fact that modern 
telescopes tend to be better and larger than the old ones. I don't 
believe that the Boulder numbers have been adjusted at all.  I think the 
telescope used at Boulder is about 20" but I'm not sure.  Naturally, up 
to a point, the larger the telescope the higher the number of sunspots 
seen.  The AAVSO gets sunspot counts from several observers.  I 
understand each observer has a correction factor to make his numbers 
comparable to Zurich.  The Zurich numbers have been using a similar 
process for centuries. So when you see sunspot numbers you have to be 
careful to compare them to like numbers.

The numbers I used I believe are Zurich numbers but I can't be 
positive.  The number I've seen for the maximum daily sunspot number is 
about 350.  The high monthly average is 286 for March 1958.  The high 
smoothed number is 201.  Admire these numbers but use with care - I'm 
not sure they all relate to each other!

The 10.7 cm solar flux numbers I have are much more accurate. They came 
from a paper "A Working Collection of Daily 2800 MHz Solar Flux Values 
1946 - 1973" by Arthur E. Covington of the National Research Council of 
Canada.  !946 is the start date because that is the day when they 
recorded the first 10.7 cm solar flux measurement.  While we only see 
the number there are actual units associated with these numbers so the 
numbers don't depend on an observer and are comparable no matter what 
equipment is used. The highest daily value was 383.4 on 23 Dec 1957.  
The highest monthly average was 286.5 for Dec 1957.  There were 27 days 
with a solar flux above 300 between Sep 1957 and Apr 1958.

Remember that neither the 10.7 cm solar flux nor the sunspot number have 
any effect on the ionosphere and HF propagation, they are just 
convenient to observe or measure and give us a general idea of the level 
of solar activity.  What really counts is the EUV and X-ray flux which 
we've only been able to measure since we've been able to get above the 
earth's atmosphere.

Kerry