COMPARATIVE CORRELATIONS OF foF2 
WITH "IONOSPHERIC SUNSPOT-NUMBER" 
AND ORDINARY SUNSPOT-NUMBER
Terr Mag 53(1) 79 (1948)
M Lindeman Phillips 

The elimination of data for 1945 and later from the compilation for correlation-coefficient, however, does not result in significantly closer approximation of the two correlation-coefficients, so that the better correlation of foF2 with "ionospheric sunspot-numbers" seems to occur not because both "ionospherie sunspot-numbers" and foF2 depart similarly from a linear relation with Wolf sunspot-numbers, but because of either the fact that "ionospheric sunspot-numbers" are more consistent than are ordinary sunspot-numbers, or, more fundamentally, that worldwide ionospheric variation is more consistent than is the appearance of sunspots. 


JGR 57(4) 473 (1952):
THE DIFFERENCES IN THE RELATIONSHIP BETWEEN IONOSPHERIC CRITICAL FREQUENCIES AND SUNSPOT NUMBER FOR DIFFERENT SUNSPOT CYCLES 
BY S. M. OSTROW AND M. PoKempner:
Analysis of data for Washington and Watheroo indicates differences in the relationship between foF2 and sunspot number for the current and preceding sunspot cycles. The sunspot number is therefore not entirely satisfactory as an index for ionospheric variations. Consequently, ionospheric data for the current cycle only should be used in preparing ionospheric radio propagation predictions whenever possible. 


Waldmeier JGR 64(9) 1347 (1959)
This [1957] is by far the highest sunspot-maximum on record since the beginning of the Zurich statistics in 1749. This high activity is produced by a very large number of small and middle-sized groups, whereas groups of exceptionally large dimensions were completely missing. Table 2 gives the numbers of sunspot-groups on each day for the year 1958. The yearly mean of the group-numbers is 14.9 against 14.3 in 1957. Whereas the sunspot-numbers decreased by 3 per cent from 1957 to 1958, the group-numbers increased by 4 per cent. 


Station: CH958 CHURCHILL
   Data Range: 8/1943->3/1996  (Total Months=632)  Parameters with data: 1
   Months with data=573  without data=59  (Released=573 Pre-release=0)

00 foF2         Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
                1943                              R   R   R   R      
                1944  R   R       R   R       R   R   R   R   R      
                1945  R   R       R   R       R   R   R   R   R      
                1946  R   R       R   R       R   R   R   R   R      
 [...]
                1993  R   R   R   R   R   R   R   R   R   R   R   R  
                1994  R   R   R   R   R   R   R   R   R   R   R   R  
                1995  R   R   R   R   R   R   R   R   R   R   R   R  
                1996  R   R   R                                      

Station: OT945 OTTAWA
   Data Range: 1/1942->3/1996  (Total Months=651)  Parameters with data: 1
   Months with data=646  without data=5  (Released=646 Pre-release=0)

00 foF2         Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
                1942  R   R   R   R   R   R   R   R   R   R   R   R  
                1943  R   R   R   R   R   R   R   R   R   R   R   R  
                1944  R   R   R   R   R   R   R   R   R   R   R   R  
 [...]
                1993  R   R   R   R   R   R   R   R   R   R   R   R  
                1994  R   R   R   R   R   R   R   R   R   R   R   R  
                1995  R   R   R   R   R   R   R   R   R   R   R   R  
                1996  R   R   R