“Since 1958 direct measurements of the outer reaches of the earth’s field by means of artificial satellites and rocket probes have convinced many geophysicists that the simple picture of that magnetic field must be drastically revised. Far from being free of external influences, the geomagnetic field is continuously buffeted by a ‘wind’ of electrically charged particles emanating from the sun, distorted by electric currents circulating in the radiation belts that girdle the earth. The net result of all these influences is a geomagnetic field shaped somewhat like a teardrop with a tremendously elongated tail. Analysis of the data provided by the satellite measurements has progressed to the stage at which the broad outlines of the magnetosphere can now be mapped with reasonable accuracy.”

Scientific American, March 1965

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