1923. No. 9. AURORAL SPFXTRA AND THE GREEN AURORAL LINE. 5 



Tims tl^.e lines hcloni^inj^- to the line spectrum of Xitroj,aMi compared 

 with those of the nej^ative hands are somewhat stron^^'-er near the upper 

 limit. 



The intensity of the i(iccii line as compared i>.'ith that of the stron» 

 negatii'e X-lmnds is qitite as lai'^e near the J>nttoni ed'^e as it is so — So 

 km. higher up in the atmosphere. 



If there is a chai^ge of relative intensity it is quite small, and goes 

 in such a direction as to make the negative X-hands stronger as we 

 pass ui)wards. 



From this result we can immediately draw the conclusion that the 

 green line cannot be produced by a gas lighter than Nitrogen, sucli as 

 Hydrogen, Helium, and Neon., and the assumption that it should be 

 emitted from a light hypothetical gas "Geocoronium" must be given up 

 as impossible, and hence forth I think Geocoronium ought to disappear 

 from the geophysical literature. 



On the cth.er hand the green line cannot l)e emitted from a gas 

 heavier than N for any gas that might come into consideration 

 (e. g. Oxvgen) would produce a greater diminution of the relative 

 intensity of the green line than that actually observed. 



The only possible li'ay of interpreting the results seems to he that 

 the green auroral line is emitted from Nitrogen ^ 



The small intensity variations observed may be explained from 

 change of densitv of th.e gas and of the velocity of the electric rays 

 that produce the luminosity, because the rays will loose kinetic energy 

 along their path through matter. 



It seems also very likely that the three otlier unknown lines 4182. 

 3432, 3208. ai:d thus all auroral lines as yet observed — are to l>e 

 ascribed to Nitrogen. 



Xutc added to the fraof: 



It should be noticed that the interpretation of the results of our spectral ana- 

 lysis here given, is based on the assumption that, in the stratosphere, the pressure 

 of any component of the mixture varies according to equation (i). This involve-; 

 that the vertical air motion is small as compared with the velocity of diffusion. 

 If this is not the case the components would get mixed through vertical currents, 

 and we should expect the composition of the atmosphere to be nearly indipendent 

 of altitude. 



This consequence would so far be in accordance with our results ; for there 

 should be no layer cf light gases on the top of our atmosphere, and Nitrogen should 

 remain the most prominent also in the auroral region. 



With regard to the green line it must in any case, on account of its greit 

 intensity, be emitted from some component present in relatively large quantities, 

 and being the strengest of all lines it should most likely belong to Nitrogen ; but 

 in this case also Oxygen might be present in the auroral region with a fairly large 

 concentration, and we should also have to consider, whether the green line possibly 

 might originate from Oxygen in some state or modification. 



