NO. 8 



I5AR0METKIC PRESSURE — DLEI.L ANO DUEIX 



for the disturbed days themselves. On this map, too, no significant 

 l)ressure difTerences are discernible. The picture is dominated by 

 a zero isoline, which covers nearly the whole Euroj)can continent. 

 The greatest pressure dilTerence within this pressure field is only 1.6 

 nib. Quite another picture is demonstrated by figure 7, wliich shows 

 the same conditions as the preceding figures, but for the first day 

 after the disturbed days. 



The Averoge Behoviour of Seo-Level Pressure 



OS reloted to oil ( 320) those Doys when the Ionosphere was 

 porticulorly Disturbed ond to oil ( 320) those Days when the 

 Ionosphere was porticularly Undisturbed; demonstrated 



by Meons of Difference - Curves ("Oisturtjed minus 

 Undisturbed") ^,„,.,„,„„. „ „, ,5 ,„,. ,^ ,^ 



S«n. Activity (rS40)o(lh« Period 

 m» 1906 - 1937 



\ /■ 



Even Years 



■^ 



\ ' 



-y*^.^ 



/\ 



\J 



\ 



-3 -I 



••for* 



V/ 



Kiev 



•I •3 'i *7 *9 .11 

 Bait Afltr 



All Years 



Odd Years 



Fin. 3. 



A considerable gradient with a maximum pressure dilTerence of 

 2^.~ ml), has been built up over the North Atlantic, in the direction 

 XW. to SE. There is a plus-area over Iceland of -f 2.1 nib. and a 

 minus-area over the Gulf of Bothnia of —1.6 nib. The direction of 

 this additional gradient is sucli that the normal average gradient, 

 as computed from long-period means (see fig. 4), is flattened by 

 it. In figure 8 we see the average additional sca-Ievel pressure field 

 2 days after ionospheric storms. The pressure gradient, directed from 



