Solar particle observations inside the magnetosphere during the 7 July 1966 event

Observations of protons emitted by the 7 July 1966 solar f l a r e a t W34, W47 with the low-altitude--high-latitude University of Iowa s a t e l l i t e Injun I V show the following.( a ) High energy -27 MeV) protons a r r i v e promptly over the e a r t h ' s polar caps ' E* and decay i n a manner consistent with diffusive propagation.(b) The counting r a t e due t o protons i n the i n t e r v a l 0.52 < E and moving normal t o the magnetic vector shows a double plateau a s the s a t e l l i t e moves over the polar caps."knee" for protons i n the above energy i n t e r v a l varies from L -7.5 t o L -6.3 a t magnetic l o c a l times of -4.5 hours and -11.5 hours, respectively.(d) After the sudden commencement the l a t i t u d e gap between trapped protons and solar protons disappears, < 4 M e V -P -( c ) The position of the suggesting that some solar protons may become trapped i n the e a r t h ' s radiation b e l t s .detectors inside the magnetosphere (Injun I V ) and outside the magnetosphere (Explorer 33) show t h a t low energy ( -0.5 MeV) ( e ) Simultaneous observations with similar protons have e s s e n t i a l l y immediate access from the interplanetary space t o the polar caps of the earth.implications of these r e s u l t s are discussed. Finally, the t h e o r e t i c a l