The first idea of a magnetic cavity around a planet (the earth) was first postulated by Chapmanand Ferraro already in the early thirties. The interest in studies of such a magnetic cavitywhich is caUed "magnetosphere” was reinforced since the accidentai discovery of the nonthennalJovian decametric radiation (DAM) by Burke and Franklin (1955). However, it was Shainalready in 1950 who first observed a radio émission at 18.3 MHz, but it was not yet attributedto Jupiter. This radiation indicated that Jupiter exhibits an intrinsic magnetic field, wherebythe radio émission is caused by électrons spiralling around magnetic field Unes in the vicinity ofthe planet, finding confirmed by the discovery of the Jovian decimetric radiation and the earth’sVan Allen belts by the sateüites Explorer 1 and 3 in 1958.no abstrac