200 AimUAL REPORT SMITHSONIAN INSTITUTIGN, 1942 



Table 1. — Great magnetic storms * 



1 Table 1 is an extension of one appearing in Geomagnetism, by S. Chapman and J. Bartels. 

 3 Expressed in minutes of arc for declination and in y (l-y=0.00001 gauss) for horizontal and vertical 

 components. 



The first of the nine great storms listed is the classic storm of 

 August 28 to September 7, 1859. Carrington and Young over 80 

 years ago interpreted certain features of that storm as indicating the 

 simultaneity of solar eruptions and magnetic disturbances, but this 

 opinion was abandoned by other investigators because they looked 

 for it in vain in later great magnetic storms. If the radio fade-outs 

 had not given such strong evidence of ionospheric disturbances simul- 

 taneous "with solar eruptions, it is not impossible that the compara- 

 tively small, though distinct, terrestrial magnetic effects would still 

 have escaped detection. Because of the rarity mentioned, and not 

 only for historical reasons, it may be of interest to recall here the 

 original records of the classical case which started the controversy. 



The records for 3 days show comparatively quiet conditions on 

 August 30 and 31, 1859, the brief baylike disturbance beginning at 

 IP 18™, September 1, and the outbreak of the second great storm at 

 4'' 50™, September 2. General Sabine stated that "this great mag- 

 netic storm, for excessive violence of character and length of dura- 

 tion, had never been surpassed by any similar phenomenon which 

 has occurred in my long and varied experience." 



R. C. Carrington's report included a drawing showing the large 

 spot in heliographic latitude 20° north and near the central meridian 

 on September 1, 1859. He noted in particular two patches of in- 

 tensely bright and white light of brilliancy fully equal to that of 

 direct sunlight. The instant of the first outburst was within 15 



