A large diurnal variation of the geomagnetically trapped radiation

t o "he satellite Injun I was used to find the high latitude termination of trapping of electrons with energy E Z 40 keV at lo00 km altitude over North America.average, this termination is at L -16 or A local day and at L ., 8 o r A I 69" in the local night.consequence, in the range 8 5. L 5 16 or 69" 5 A 5 75" , the average intensity of trapped electrons is some one hundred On the -75" in the As a times greater in the local day than it is at local night.Several explanations are suggested but none is proven.results show that McIlwain's L parameter loses its simple applicability for L 2 6 or A The ? 66".