ANALYSIS OF THE IONOSPHERE 



481 



back from E while the o-signal goes on to F or from Fi while the 

 o-signal goes on to F2, or from F2 while the other goes irretrievably 

 forth into space. 



When the northwest-southwest antenna is used, the ionosphere 

 takes charge of the signals, and separates them into an o-component 

 and an x-component. Each travels according to its proper law, and 

 the x-component reaches its lower-down mirror earlier and beats the 

 o-component back to earth. Two echoes return instead of one. 

 The earlier is plane-polarized with electric vector east-and-west; the 

 laggard is plane-polarized with electric vector north-and-south. 

 Suppose a long straight horizontal antenna is used to respond to the 

 returning signals. It will respond to both, if pointed north-west- 

 southeast; only to the earlier, if pointed east-and-west; only to the 

 later, if pointed north-and-south. 



All the foregoing were statements of theory at first, but thanks to 

 the experiments of Wells and Berkner at Huancayo, they now are 

 statements of data as well.^ Figure 13 exhibits a small selection from 

 the data. 



RECEIVE 

 TRANSMIT 



NW- 

 SE 

 NW- 

 SE 



N-S 



NW- 



SE 



NW-|| NW- 



SE II SE 



NW- 

 SE 



NW- 

 SE 



NW- 

 SE 



NW- 



SE 



=i 500- 



P 300- 



m0H0^^^tdl^!l 





. -^.».. 



l^^ 





10 . loh 35m 



75° WEST MERIDIAN TIME IN HOURS 



12 



Fig. 13 — Echoes of plane-polarized signals near the geomagnetic equator. 

 (Wells and Berkner.) 



Now look again at Fig. 4: formerly I asked the reader to ignore 

 one of the curves, but now we will compare the two. The circles and 

 the crosses indicate the o-wave and the x-wave respectively. One is 



^ This is a good place to speak of a question which may already have occurred 

 to many readers, viz. the question why we assume the charged particles in the 

 ionosphere to be free electrons rather than charged atoms or molecules. Were 

 they of atomic or molecular mass, the separation of the and x echoes would be 

 inappreciable, and the "gyro-frequency" later to be mentioned (page 482) would 

 be quite outside of the radio range. It is not, however, excluded that among the 

 free electrons there may be a great multitude of charged atoms, perhaps even many 

 times more numerous than they, though much less influential. 



