COSMIC RAYS FROM THE SUN — GOLD 



237 



important chains of stations — one belonging to the Carnegie Institu- 

 tion and run by Dr. Forbush, and the other by Dr. Simpson of the 

 University of Chicago. The great number of stations around the 

 globe is important if one wishes to infer the directions of the particles 

 before they entered the earth's deflecting magnetic field. 



There occurred another new phenomenon on this occasion. The 

 cosmic-ray stream was so intense that it changed the electrical prop- 

 erties of the upper atmosphere in a way that had never happened 

 before. Even on the night side of the earth low-frequency radio 

 communication was severely affected, and in high-latitude regions 

 most or all radio contact ceased. This was presumably the effect which 

 caused the British Admiralty to announce that it had lost contact 

 with a submarine in arctic waters, and had ordered a search. The 

 submarine was in fact quite all right, and was probably baffled also 

 by the absence of a reply from the Admiralty. 



Figure 1. — Diagram illustrating how particles that embarked on spiral orbits of different 

 pitch will be delayed differently and why late arrivals will appear to come from a variety 

 of directions different from the main direction. The size of the earth is small compared 

 with the radius of the spirals. 



This cosmic-ray outburst not only is an interesting event but also 

 it can be used to tell us something of the condition of the tenuous 

 gas that fills space between the sun and us. For a number of years 

 now, physicists and astronomers have been discussing the reasons 

 why they supposed very extended magnetic fields to be carried by all 

 the very tenuous gases in the galaxy and of course also by the some- 

 what denser gases of the solar system. But there has not been any 

 other observation that was so clear cut in indicating these fields. 

 Here we saw that particles that had almost certainly started their 



