2. Correlation Coefficient Dependence on Magnetic Activity
[12] Vanina and Danilov [2003]
analyzed the behavior of
r(foF2) for
magnetically quiet days with
Ap < 8.
Vanina-Dart and Danilov [2006]
considered in detail the
r(foF2) dependence on the magnetic activity on
the basis of the data for the same stations and same period (1979-1980)
as given by
Vanina and Danilov [2003].
Using a special program, the
r(foF2) values were calculated for three-month intervals for the days
with the geomagnetic
Ap index less than 6, 8, 12, 16, 20, and 30. The
number of days with
Ap < 30 actually coincide with the number of days
in the month, so there was no sense in increasing the
Ap boundary
further.
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Figure 3
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[13] Figure 3 shows variations in
r(foF2) at Moscow station in 1980 at
different limitations to the
Ap value. One can easily see that the
maximum negative values of
r(foF2) are observed at the most strong
limitation on magnetic activity:
Ap < 6. At the increase of the boundary
value of
Ap (that is, at the including into the consideration more and
more magnetically disturbed days) the absolute value of
r(foF2) decreases. Nevertheless, even for
Ap < 20 and
Ap < 30 the
r(foF2) value
obtained within the spring minimum in April is still significant at the
99% level by the Fisher criterion.
[14] A typical feature of Figure 3 is that the
r(foF2) curves for
different limitations on
Ap repeat each other in the shape. For all
Ap a
spring maximum in negative values of
r(foF2) and a fall decrease in this
value are observed.
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Figure 4
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[15] Figure 4 shows a similar picture for Kaliningrad station. For the
sake of clarity, only the first half of the year is shown. This makes it
possible to see better the effect of the decrease in the maximum negative
value of
r(foF2) in April at the increase of the boundary value of
Ap.
Thus the comparison of Figures 3 and 4 demonstrates that the variation
in the maximum negative value of
r(foF2) occurs identically at both
(Moscow and Kaliningrad) stations: with the increase in the boundary
value of
Ap the amplitude of the spring minimum decreases
monotonically. Results similar to Figures 3 and 4 were obtained also for
stations Gorky, Tomsk, Khabarovsk, and Alma-Ata.
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Figure 5
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[16] The dependence of the maximum (by the absolute value)
correlation coefficient
r(foF2) max on the boundary value of
Ap seen in
Figures 3 and 4 is visually illustrated by Figure 5. One can see that the
depletion of
r(foF2) max with an increase of
Ap is of the same character for
both stations and is statistically significant (the coefficient of the
determination for both curves is 0.93-0.94 which provides a high
significant level according to the Fisher criterion).
[17] Thus we may state that at other equal conditions the correlation
between the daytime and nighttime values of
foF2 is the better
pronounced the geomagnetically quieter is the considered period.
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