NO. 8 BAROMETRIC PRESSURE — DLEI.L AND DUELL IQ 



it may give rise to regionally intensified heat emission of the strato- 

 sphere, which, according to G. Stucve (27), may cause the develop- 

 ment of independent islands of high air pressure. According to 

 S. P. Chromow (28), transformations of the large-scale weather 

 situation may be produced by such processes. 



Figure 16 gives a concentrated summary of the difTerent hy- 

 potheses which have been postulated to explain the effect of solar par- 

 ticles invasions upon the stratospheric-tropospheric circulation and 

 large-scale weather situation. An evaluation of such effects should 

 never be undertaken without regarding the fact that the result of 

 these influences will always, in a high measure, depend on the initial 

 state of the troposphere and on the amount of potential energy 

 which is available for release by ionospheric-stratospheric processes. 

 It is quite possible that the effect of a particle invasion at one time 

 will remain without any consequences, and on another occasion, when 

 all involved factors stand in an optimal proportion to each other, 

 will g've rise to a complete change in the large-scale weather situation. 

 1' urthermore, it is probable that the occurrence frequency and the kind 

 of succession of such particle invasions, and, in addition, the inter- 

 fering appearance of ultraviolet invasions, will be of decisive 

 imjX)rtance for the efficiency of each single particle invasion. 



II, RELATIONSHIP BETWEEN SOL.\R ULTR.AVIOLET 

 IXV.XSIONS .\XD SE.\-LEVEL PRESSURE 



A. Origin of Solar Ultraviolet Invasions 



Solar ultraviolet invasions occur during l)right chromospheric 

 eruptions. These appear generally in connection with certain suns}x)t 

 groups, at the outer margin of the penumbrae. The number and 

 intensity of the eruptions depend closely on the type and phase of 

 development of the sunspot groups. The international indices for 

 the intensity ("i," "2," and "3") correspond to an average life 

 duration of 20, 40, and 60 minutes and to average areas of 1.2 x 10 *, 

 3.8x10*, and I0.2XIO-* fractions (^1:3:9) of the apparent sun 

 disk. The brightness generally increases with the size of the eruption. 

 The wave radiation of these eruptions consists chiefly of the emission 

 lines of hydrogen, helium, and calcium. It has been possible to con- 

 clude from the results of prominence research and ionosphere research 

 that the intensity of this ultraviolet radiation per unit of the eruption 

 area is about 10' times as strong as that ultraviolet intensity which 

 has been computed on the basis of Planck's radiation formula for 

 the same spectral range and for an undisturbed sun. By these proc- 



