SUN AND THE EARTH'S MAGNETIC FIELD^ — FLEMING 193 



month shows the recurrence tendency equally well, with the initial 

 and repeated peaks after 27 days inverted because their character 

 figures are below the average. 



A modification of this method consists in charting character figures 

 for all days for a number of years. On such a chart, in order to com- 

 pare the magnetic character with conditions on the sun, which rotates 

 once in about 27 days, appropriate symbols indicating the magnetic 

 character of each day are placed in rows, the date of the first day in 

 each row being indicated at the left, and each successive row beginning 

 27 days later. In order to emphasize the continuity of the series, the 

 symbols showing magnetic character for the first 9 days of the next 

 row are repeated. Charts of this kind show vertically elongated 

 clusters covering one or more rotation periods. Similar time patterns 

 for the sunspot cycle indicate this cycle to be more strongly manifested 

 on the sun than in geomagnetic disturbance. In this method, devel- 

 oped by Bartels, one may concentrate graphically information 

 obtained during many years by the world net of magnetic and astro- 

 nomic observatories. The magnetic clusters are at times found to be 

 more pronounced for periods when the sun is free or almost free 

 from spots. Even for periods when both are disturbed the respective 

 time patterns are often very different. Therefore, it is clear that 

 sunspot numbers are not always a good index of any solar agencies 

 that cause magnetic disturbance on the earth. Thus, further research 

 on this interrelation calls for a more all-inclusive measure of solar 

 activity than that of the sunspottedness, a matter for the solution 

 of which we must look to the astrophysicist. 



Whatever theory of magnetic disturbances may finally be evolved, 

 it is clear that geomagnetism provides us with information regarding 

 fairly persistent solar phenomena, restricted to varying but always 

 well-defined regions on the sun's surface. These are not only of inter- 

 est for study of the sun, because direct astrophysical observations do 

 not reveal them as yet, but are of even greater interest from the 

 terrestrial standpoint because magnetism records these solar influences 

 only in so far as they actually affect our globe. 



IONOSPHERIC AND SOLAR RELATIONS 



The conclusion drawn from magnetic variations and disturbances 

 and from polar lights that they have their origin in electrical phe- 

 nomena at great heights in the atmosphere makes it of interest to 

 study the electrical conditions there. Since we are unable to visit 

 these great altitudes, we have to study the electrification of the upper 

 atmosphere, or ionosphere, from our position on the earth. 



More than GO years ago Balfour Stewart inferred from geomag- 

 netic data the existence of regions in the outer atmosphere of great 



