2 kvo 



Theory of Magnetic Storms. G77 



eV 

 and i the chemical constant. If T = 6000, =26'8. The 



atomic heat o£ the atoms is presumably 



5/2R-3rH^ =5/2R, 



since 777? > 2G*8. That of the ions mav probably be put 



/»t ^T n'T 

 equal to 5/2R, so that the term I -. , - 1 SCpdT reduces to 



Jo «. 



•5/2 log T. The chemical constant i has been shown to be 

 2303 ( — 1, + 3/2 log A), A being the atomic weight, in nil 

 monatomic substances examined. Whether this may be 

 extended to electrons, however, appears extremely doubtful, 

 for if it were permissible the chemical constant of electrons 

 would be —15, and the thermionic emission would be re- 

 duced by a factor of the order 3*1. 10~ 7 . If the term 

 3/2 loo- A is neglected in the case of electrons %i= —3*7 and 

 K=- 1 



X ^P 6000* 



Now K„= — -- „P where x is the fraction dissociated and 

 1 — ay 



P the total pressure, whence if n is the number of atoms 



per unit volume, 



K p -nkt 



Obviously therefore ionization becomes important when nkT 

 is of the same order as or smaller than 1\^ ; in the present 

 case therefore where T = 6000°, ionization would be almost 

 complete when n = 10 s . Though this estimate is extremely 

 rough on account of the uncertainty about the chemical 

 constant, it is clear that the cloud of gas would become 

 ionized and therefore fade out of sight when the pressure 

 became sufficiently low. 



The next question to be examined is what modification in 

 constitution and shape these clouds of ionized gas are likely 

 to experience on their way from the sun to the earth. 

 Taking the speed as 8.10 7 cm./sec, a velocity often ob- 

 served, the time in transit would be about 1*9. 10 5 seconds. 

 This is in good accord with the value found by Ricco, who 

 arrived at a time 1'5. 10 5 seconds by comparing the passage 

 •of sun-spots with the occurrence of magnetic storms. The 

 most important question as regards constitution is the 

 amount of recombination to be expected. Taking hydrogen 



