SUN AND THE EARTH'S MAGNETIC FIELD — FLEMING 205 



verge toward what is called the magnetic zenith just as railroad tracks appear 

 to converge toward a point on the horizon. 



Photographers in Long Island and New York State obtained 

 negatives, and through their courtesy I am happy to exhibit copies 

 which fully justify Mr. McNish's account as regards brilliancy and 

 variety of the auroral activity. 



The bright chromospheric eruptions in sunspots photographed in 

 the light of luminous hydrogen vapor show the bright eruption start- 

 ing on September 17 at 6:26 a. m. Pacific standard time, and the 

 greatly increased brightness of the eruption 10 minutes later. 



COSMIC-RAY RELATIONS 



A connection between geomagnetic and cosmic phenomena has 

 recently been discovered — the world-wide decrease in the intensity of 

 cosmic radiation during great magnetic storms. Although such an 

 effect was predicted over 6 years ago, observational verification was 

 not achieved until the occurrence of the great magnetic storms of 

 our present sunspot cycle. The effect was noted by Forbush during 

 the great storms of April 1937, March 1940, and September 1941. 

 Since the magnetic moment of the eartli increases during the main 

 phase of a magnetic storm, a decrease of cosmic radiation during that 

 time is to be expected on the basis of the well-established variation 

 of cosmic-ray intensity with geomagnetic latitude. 



The superposed-epoch method is useful also to show correlation 

 between cosmic radiation and the geomagnetic field. Time variations 

 of cosmic-ray intensities, whose origin probably is deep in space, are 

 now measured to within a fraction of 1 percent. This made possible 

 a real comparison with geomagnetic changes by Broxon in 1941. He 

 showed the simultaneous average variations of cosmic-ray intensities 

 and of international daily magnetic character figures by superposed 

 epochs of supernormal and subnormal cosmic-ray intensities. The 

 cosmic-ray intensity is practically always lower for the five interna- 

 tional magnetically disturbed days than for the five international 

 magnetically quiet days of each month. These results confirm the 

 inverse correlation between cosmic rays and magnetic disturbances 

 as previously shown by Forbush. 



The 131/^-day and 27-day waves in cosmic-ray intensity are closely 

 associated with those for character figure and magnetic horizontal 

 intensity. This directs attention to a possible means by which cosmic- 

 ray data might serve to establish the existence of a general solar 

 magnetic field. 



LABORATORY APPROACH 



Most recent of promising attacks on the many problems indicated 

 above is in the laboratory through investigation of the laws govern- 

 ing the interaction of the magnetic particles composing all matter. 



