236 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 7 



1956. There occurred then a very large flare just near the edge of the 

 sun. It was seen in Japan and India (not here, as it was the middle 

 of the night) and it was recognized by the Japanese observers as a 

 most spectacular event before they knew of any of its other effects. 

 The flare was so bright that it could be seen without the usual spectral 

 filters, just as a bright spot on the sun's surface. Beyond the nearby 

 edge they reported seeing a bright fan-shaped structure and nothing 

 like this has ever been seen before. The radio-noise observations indi- 

 cated a major outburst and one that was extraordinary in that the 

 disturbance seems to have reached a very great height in the solar 

 corona. There was a complete f adeout of high-frequency radio com- 

 munication over the sunlit side of the earth and there was the char- 

 acteristic magnetic effect that indicates when very intense ultraviolet 

 light has struck the outer atmosphere of the earth. All this was the 

 common pattern of events, just very intense. But about 15 minutes 

 after the beginning, the cosmic- ray rate suddenly began the sharpest 

 increase and then reached the highest level that has ever been known. 

 This occurred all over the earth, not only on the side facing the sun. 

 The reason for this is, of course, that cosmic rays are charged particles 

 and are therefore deflected by the earth's magnetic field to get right 

 around to the back. After a further 15 minutes, the peak was reached 

 and its intensity was such that about two hundred times the usual 

 number of cosmic-ray particles hit the earth every second. The rate 

 then decreased, but much more gently than it had risen. After a few 

 hours it returned nearly to normal. 



In a world that is very conscious of radiation disease, one should 

 explain that this does not constitute a serious attack on us. The total 

 amount of radiation that every person received in those few hours 

 was still very much less than we take in during an X-ray examina- 

 tion. On the other hand, if the sun were ever to decide to continue 

 this kind of stream on a steady basis, it would undoubtedly be very 

 harmf ul to us. But we can take it that this is not very likely, judging 

 alone from the good continuity of biological development that seems 

 to have happened in long periods on the earth. 



I am reminded just how striking an event this was when I think 

 of all the trouble to which we went to check the recording equipment 

 before believing its answers. That morning I came in to work and 

 my assistant was eagerly awaiting to tell me that during the night 

 this enormous increase had taken place. He was used to looking for 

 changes of y 2 percent or so, and there was a change of over 100 per- 

 cent recorded. Everything was tested before we dared to announce 

 this as real ; and then a little later all the other reports of the event 

 started to come in. In all, some 40 cosmic-ray recording stations all 

 over the world produced useful records, including, of course, the two 



