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The Upper Boundary of the Van Allen Radiation Belts.


THREE measurements have now been made of the intensity and extent of the Earth's upper radiation belt and of the primary cosmic-ray intensity beyond. These were made by: (1) the American space probe, Pioneer III (December 6–7, 1958, ref. 1), (2) the Russian cosmic rocket, Mechta (January 2–4, 1959, ref. 2), and (3) the American space probe, Pioneer IV (March 3–6, 1959, ref. 3). Since the radiation belts vary with time, the three experiments give different results for the intensity of the belts, but the measurements of cosmic-ray intensity beyond the belts ought to be comparable. Nevertheless, preliminary results of the Pioneer tests seemed to indicate a difference in cosmic-ray intensity of almost a factor of 2. This communication discusses the resolution of this discrepancy and some new data bearing on the spatial extent of the trapped radiation.

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Snyder, C. The Upper Boundary of the Van Allen Radiation Belts.. Nature 184, 439–440 (1959).

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