On Kapid Periodic Variations of Terrestrial Magnotisui. 33 



30. From all we have discussed at length in the preceding 

 paragraphs, we can as yet draw no convincing conclusion 

 regarding the actual mechanism producing the magnetic pulsations 

 in question. Many things, indeed, turn on the crucial observation 

 regarding the universal simultaneity of the periodic phenomena. 

 If it be ^rovecZ ultimately beyond doubt as seems proljable, there 

 remain only those hypotheses at disposal, which lead to the 

 simultaneous occurrence of the phenomena for an area of 

 considerable extent. It that case, the magnetic waves may 

 probabl}' be explained by the combinat'w7i of 2^(^r iodic fluctuations^ 

 in intensity as ivell as in position and inclination of the atmospheric 

 current, which is then to be considered of rather diffused, but 

 not of linear character, having the maximum intensity near the 

 equator. The origin of these fluctuations might then very 

 probably be sought in the vertical stationary oscillation of limited 

 portions of the upper atmosphere accompanying the diurnal 

 oscillation of the entire atmosphere.^-* 



At any rate, it must be admitted that the present results 

 of observation refer to a single station, and the observations are 

 far from being complete. A further study of the allied pheno- 

 mena, es2:>ecially the simultaneous observations in at least three 

 stations, sufficiently apart from each other, will be desirable. 

 The results will not fail to advance our knowledge on the nature 

 of the atmospheric current of which we have at present only a 

 ver^^ vague idea. The interest attached to the problem at hand 

 is by no means confined to the limited subject of terrestrial 

 magnetism. The phenomena have a mucli wider bearing than 

 at first sight appears, on various interesting problems in different 

 branches of physics, for examples those regarding solar physics, 

 meteorology and also especially those regarding the electrical 

 and mechanical behaviours of highl}' rarefied gases under the 

 action of different kinds of radiation. 



In conclusion, the author wishes to express his sincerest 



1) In this case, however, the phenomena of the propagating auroral bands accompanied 

 with no corresponding magnetic maves, become rather incomprehensible and throw some 

 doubt on Birkeland's original conception pertaining to the nature of the luminous band. 



