REMARKS. 



From a survey of the auroral material gathered both from Arctic and from 

 Antarctic regions, it does not appear that any very groat advance in our knowledge 

 is likely to accrue from direct observations of aurora) at isolated stations, unless 

 magnetic data are available for comparison. It appears, in fact, as if the diiel advance 

 in our knowledge re^aiding auroras is likely to be made through a searching study ol 

 the causes of magnetic disturbances, and it is certainly dillicult to escape the conclusion 

 that these disturbances owe their origin to charged part-ides projected from the sun. 

 It seems particularly desirable to emphasise the fact that there is no indication of 

 the successive arrival of negatively and positively charged particles* in the earth's 

 atmosphere, the maximum magnetic and auroral disturbances in Polar regions 

 occurring at about the same time, on the average. 



It does not seem out of place to emphasise the fact that striking auroras can be 

 seen in the auroral zone without the occurrence of a corresponding magnetic 

 disturbance, particularly in the early morning, the closest correlation between 

 magnetic disturbances and aurora being in the late afternoon. It is certainly 

 interesting to note that the general maximum of magnetic disturbance falls not far 

 from magnetic local noon, the secondary maximum near magnetic local midnight 

 appearing only during the winter months. 



It is necessary to bear in mind that it is not essential for a local auroral display, 

 however striking, to give rise to a magnetic disturbance of significant amount, even 

 if the prime cause of the two phenomena is identical. In fact, the magnetic 

 disturbance is likely to depend almost as much upon extent as upon intensity of 

 precipitation of the solar particles. 



It is at least open to consideration whether the prime causes of the two 

 phenomena are identical, and it must be admitted that we have every right to assume 

 that auroras can be seen somewhere on the earth's surface every day, and at every 

 moment of the day. This would demand a continual influx of solar particles from the 

 sun. The magnetic character number corresponding to the occurrence of very faint 

 auroras is less than the mean of all hours, and this seems to lend support to the 

 contention that the incidence of aurora somewhere in the auroral zone is a 

 continuous phenomenon. 



There can be little doubt that the relation between magnetic storms and auroras 

 exists in virtue of the same or a similar projection of energy 1mm the sun and the 

 possibility exists that it is only in particular circumstances that the particles (v.lpch 

 must be charged, in part at least) meet the atmosphere in low latitudes and are 

 accompanied by severe magnetic storms outside the polar regions. 



* As pointed out by Schuster and Vegard, positively and negatively charged particles must oenir 

 together during the journey in approximately equal numbers if the particles are to reach the eaith's 

 atmosphere without dispersion. Vegard also points out that the number of each sign leaving the sun in 

 unit time must be equal. 



39 c _* 



