PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
Δ(gradt),°C/100 km
N, *100 hour -1
Nyr - N yr-1 , *100 hour -1
4400
4200
4000
3800
3600
3400
3200
400
200
0
-200
-400
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
AFZ
λ = 40°W
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Year relative to the sunspot maximum
a
Climax Neutron Monitor
19 cycle
20 cycle
21 cycle
22 cycle
23 cycle
Mean
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
b
19 cycle
20 cycle
21 cycle
22 cycle
23 cycle
Mean
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Year relative to the sunspot maximum
20 cycle
21 cycle
22 cycle
23 cycle
Mean
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
AFZ
λ = 30°W
20 cycle
21 cycle
22 cycle
23 cycle
Mean
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Year relative to the sunspot maximum
Fig.4. Superposed epoch analysis of the variations of the AFZ temperature gradients in the 11-yr solar cycles. The 0
year corresponds to the year of the maximum of sunspot numbers.
The results obtained provide evidence of the influence of solar activity and related phenomena on the
thermo-baric field structure of the high-latitude troposphere that manifests in the periodic increases of the
temperature contrasts in the Arctic frontal zone. Let us consider what may be the factors influencing the
temperature gradients.
In Fig.4 we can see a superposed epoch analysis of the variations (the deviations from the 11-yr
running averages) of the AFZ temperature gradients in the 11-yr solar cycles, the zero year corresponding to
the year of the maximum sunspot numbers. The data in Fig.4 show that in all the cycles under study the
minima of the temperature gradients are observed in the years of solar activity maxima. The greatest values
of the temperature gradients are observed in the +3/+4 yr after the sunspot maxima, i.e. at the declining phase
of solar cycle. The variations of the AFZ temperature gradients averaged over 4 cycles under study are
shown by the red thick lines. We can see that in the 11-yr solar cycle the temperature gradients in the AFZ
near Greenland vary on the average by ±0.15°С/100 km, i.e. by ±10−15% relative to the mean values.
Fig.5. Mean yearly values N of the NM counting rate in
Climax (а) and the difference of the yearly values of the
NM counting rate between the current and the previous
years (b) in the 11-yr solar cycles. The 0 year
corresponds to the year of the maximum of sunspot
numbers.
290
Let us compare the variations of the AFZ
temperature gradients with solar-geophysical
indices. It is known that GCR fluxes reduce as the
solar activity increases, the minimum of GCR
intensity is usually observed in the +1 yr after the
sunspot maximum (see Fig.5a). However, the rate of
the changes of GCR fluxes varies in the solar cycle.
The difference of yearly values of the neutron
monitor (NM) data in Climax (geomagnetic cutoff
rigidity R=2.99 GV) in the 11-yr solar cycle is
presented in Fig.5b. It is seen that GCR fluxes start
to decrease rather sharply 1 or 2 years before the
sunspot maximum, the sharpest drop in GCR
intensity compared with the previous year is usually
observed in the 0 year of solar cycle. The recovery
of GCR intensity starts in the +2 yr, and the sharpest
increase is observed in the +3/+4 yr after the
maximum of solar activity. Comparing the data on
the temperature gradient variations and the rate of
GCR intensity changes (Fig.4 and 5), we can note
their rather similar features. Indeed, the minima of
the AFZ temperature gradients are observed at the
maxima of the solar cycles and coincide with the
highest rate of GCR flux reduction. The maxima of
the AFZ temperature gradients are observed in the
+3/+4 yr after the sunspot maxima and coincide with
the highest rate of GCR intensity increase. Thus, we
can suggest that a physical mechanism of solar