Less often, daily values of the mentioned elements are correlated with each other, for example by C. All calculations are made exclusively on the basis of daily values of the solar, ionospheric and meteorological elements. Anionospheric storm is mainly characterized by a significant decrease in the equivalent electron density in the so-called F layer.
The sea level pressure data used in this part of the investigation were observed over a continuous series of 11,688 individual days. Figure i, calculated by the method of superimposed epochs, shows for these stations the average behavior of the pressure at sea level with respect to all those days (320) when the ionosphere was particularly disturbed and to all those days (320) when the ionosphere was still particularly smooth. The niacinia difference on the third to fourth day after the key dates ranges from 2.6 to 3.2 mb., which varies according to the geographical position of the station.
Figure 5 shows the asymptotic representation of the mean deviations of the sea level pressure field from the long-term averages, even a day before these disturbed days. This is almost the same value as in the days before the disturbed days, at the beginning of the whole development.
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As can be seen from the upper curve, the greatest increase of the gradient, from 1.6 to 3.7mb., occurs as early as the first day after the ionospheric storms. The lower curve of the same figure shows the iulcrdiurnal variation uf the gradient, and accordingly has its peak, with f 2.1 mh., on the fir>t. Stagg (8) found that in Lerwick on days with geomagnetic disturbances, the forenoon maximum of the daily variation of sea level pressure was lower, and the afternoon maximum higher, than on days without geomagnetic disturbances. This relationshi]).
Attempts at a physical explanation of the observed relationship In the following chapter, an attempt at a schematic description of the way in which the influence of short and long bursts of the solar particles leaving the sun will be described. A pressure effect in the direction of the shocks .. ionization; excitation of the emission of visible light, ultraviolet, .. and X-ray photons; dissociation, especially of the molecular oxygen .. production of chemical compounds in the form of condensation nuclei .. and heating of the absorbing layer. As to the magnitude of the shock-pressure effect that can be expected, no details have been known so far.
The dissociation of the oxygen molecules must be accompanied by a significant increase in pressure, provided that a sufficiently large amount of molecular oxygen is available. Deeley (12) considers this warming to be a sufficient cause for the drop in sea level pressure he observed in the Arctic regions during the peak of solar activity centers. - Its ability has been emphasized by several authors and may be important for several reasons. Secondly, under certain conditions a penetration into the troposphere of the lines of equal force originating from the ionospheric-electric field is possible.
However, such chemical compounds can also be formed during normal solar particle bombardment of a mixture of oxygen and nitrogen, especially in the presence of water vapor or hydrogen. This flow can continue up to the high stratosphere and from there can suck up the air in the center of the cyclone. The assumption of the separate existence of the troposphere, independent of the stratosphere, was thus definitively destroyed.
A local clouding of the stratosphere caused by nuclei can become important even without condensation phenomena.
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Using the 500-mb absolute topography data. surface, which have also been published in the Taeglicher Wetterbcricht of the Deutsche Seewarte for an area between 45° and 60° N. longitude, an attempt has been made to answer the question: "Does the pressure at an altitude of about 5,000 m. respond to strong ultraviolet invasions, and. The average behavior of Moximum Interdiurnol Increase in sea level pressure above me Areo 45''Nl.fo 60»NLend IG'WLto 20*Ei, os relates to oil. The three cards on the left side of the figure represents the average change in absolute topography of the 500-mb.
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The largest differences between the zero line must be duininatiii},'.. tli maximum uplift and maximum subsidence are accordingly relatively small and amount to 2.1 dkm in summer, 3.1 dkm in winter and only 1.3 dkm. for all seasons together One day after the ultraviolet invasions, the picture changed fundamentally, as can be seen on the right side of Figure 19.. the average change in the absolute topography of the 500-mb area in dkm. place i day after all very intense ultraviolet invasions from the day before those invasions. A strongly marked area of subsidence developed over western Europe and a rather pronounced area of upwelling over northern Europe.. the location of the area of upwelling is the same in winter and summer, but the area of subsidence lies slightly further south in winter and slightly further north in summer compared to the seasonal average. The uplift and maximum subsidence are relatively large and amount to 6.9 dkm. in summer 8.2 dkm. and in winter 6.9 dkm. for all seasons.
However, more comparative research is necessary before any clear conclusions can be drawn from these results. But for the future work to be done on a very broad basis, it might be desirable to extend such investigations to years further back in the past. Duell (30), the calcium flocs from the entire solar disk were finally accepted as substitutes for direct observations of eruptions.
In these statistics we do not rely on the controlling element, i.e. solar activity, but on. The reason for this was that in the case of the calcium flakes it is occasionally very difficult to select a certain number of clear and well-defined extreme values, for example the five highest figures in each month, due to the occurrence of many characteristics . numbers of equal value.
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8 BAROMETRIC PRESSURE — DUELL AND DUELL 27 namely that the number of calcium flocs increases during and namely that the number of calcium flocs increases during and shortly after bright chromospheric outbursts is consistent with our current knowledge of solar physics. Analogous to the behavior of the calcium numbers before the pressure increases, 3 to 5 days before the pressure in the sca level decreases, the number of calcium flocs also decreases, after being particularly high on average 6 days before the key dates. On the whole, it can be seen from Figure 20 that it is not entirely hopeless to use certain other solar indices instead of direct observations of ultraviolet bursts if there are no reliable observational data on the bright chromospheric bursts.
One fact is quite clear from Figures 17 to 20, namely that, unlike solar particle invasions, the influence of the ultraviolet solar invasions on sea level pressure does not seem to exist only. In the following chapter an attempt will be made to give a schematic description of the manner in which the influence of short bursts of extreme sliort-wave ultraviolet solar radiation. As some of the physical possibilities to be considered in that connection have already been mentioned, the discussion here may be confined to a few facts of special interest.
There they appear mostly in the immediate vicinity of groups of sunspots that are in a certain stage of development: No. Known geophysical sequential reactions are: "Bay disturbances" of earth-magnetic elements and electric earth current; an abnormal U-layer, the appearance of which is associated with a short-term "fade-out".
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8 BAROMETRIC PRESSURE — DUELL AND DUEI.L 2 g stratosplicrc infra-red emission wliicli would be followed by a local turbidity, produced by nuclei. and supposedly the same effect of solar ultraviolet invasions on the other hand, may be that solar ultraviolet photons penetrate much deeper into the earth's atmosphere than solar particles. This fact is of great importance in the question of solar effects on the stratospheric ozone layer. Moeller (40) pointed out that a reasonable explanation for the relationship between changes in solar ultraviolet radiation and variations in sea-level pressure would be possible by making the following assumptions: The effective infrared emission of atmospheric carbon dioxide in the spectral range between 13 and i6,u, which is important for changes in stratospheric temperature and hence for changes in sea level pressure, is strongly dependent on the amount of stratospheric ozone which also has a strong absorption band between 13 and 16 /H, and therefore more or less eliminates the emission of.
The assumption that the amount of stratospheric ozone is affected by variations in solar ultraviolet radiation is. Haurwitz also emphasizes the important role to be attributed to stratospheric ozone in the case of a relationship between solar ultraviolet radiation and sea level pressure. After the relevant calculations, he concludes that the possibility of significant pressure changes on the earth produced by solar activity can be affirmed and that such pressure changes must be accompanied by substan-.
Nevertheless, he notes that the atmosphere will respond differently to the same solar impulse depending on its initial state. W'ulf (42) emphasizes. in recent publications that show the heating of the upper atmosphere by . solar ultraviolet radiation, which is absorbed by the oxygen and ozone, together with the emission processes of the stratosyheric ozone, carbon dioxide, and perhaps even of the water water and the oxides of m'trogcn. probably rejects the most important causes for the development of meridional pressure gradients.
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CONCLUSIONS
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