SUN SPOTS AND RADIO — STETSON 



221 



a particularly good chance of the ejected electrons striking the 

 earth's atmosphere and causing an ionization, or electrification, of 

 the upper atmosphere, giving rise to an auroral display. At the 

 same time the induced earth currents will distort the earth's mag- 

 netic field, causing the small variations in the compass needle so 

 characteristic of a " magnetic storm." 



Wliile for many generations scientists have recognized the recur- 

 rent cycle in solar activity and the magnetic changes in the earth, 

 never before the present period of sun-spot activity has it been 

 possible to study so thoroughly the changing degree of electrification 

 in the earth's atmosphere with the coming and going of the spots 

 across the solar disk. All this has come about by the development 

 of the radio. 



The same electric disturbances which alter the earth's magnetic 

 field and produce the displays of the aurorae, or northern lights, so 

 change the electrical state of our atmosphere that the radio waves 

 are also afi'ected to a very marked degree by the coming and going 

 of the gigantic solar cyclones. 



1926 



March 



August 



FiGUitB 7. — Curve sbowiug correlation of sun spots with radio reception ; full curve, 

 relative intensity of radio reception on transatlantic, South American, and conti- 

 nental reception 



In the adjoining figure is a graph showing the number of sun 

 spots during the 12 months of the year 1926 and another graph show- 

 ing the average condition of radio reception over the North Atlantic 

 and the South Atlantic and across the Continent. The sun-spot 

 graph is made from the so-called Wolfer numbers and is plotted with 

 an inverted scale, i. e., the larger the numbers the shorter the ordi- 

 nate of the curve. These Wolfer numbers are based upon the 

 number of spots visible on the sun's surface at a given time and to 

 some extent upon their area, but do not take into account the posi- 

 tion of the spot on the sun's disk. The general run of these graphs 

 indicates that radio reception is distinctly impaired by an increase 

 in the sun-spot numbers. 



Quantitative measurements of radio reception since 1926 seem to 

 have established beyond much doubt that long-distance night recep- 

 tion in the broadcast zone is in general poor when sun spots are 



