Energetic Electrons in the Magnetosphere of Jupiter

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Science  25 Jan 1974:
Vol. 183, Issue 4122, pp. 309-311
DOI: 10.1126/science.183.4122.309


Observations of energetic electrons (≳ 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (RJ). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 RJ. The omnidirectional intensity J0 of electrons with energy ≳ 21 million electron volts within the region 3 〈 r 〈 20 RJ is given by the following provisional expression in terms of radial distance r and magnetic latitude θ: J0 = 2.1 x 108 exp[-(r/a) - (θ/b)2]. In this expression J0 is particles per square centimeter per second; a = 1.52 RJ for 3 ≤ r ≤ 20 RJ; and b = 15° for 3 ≤ r ≤ 10 RJ, diminishing gradually for larger r. There is tentative evidence for mild effects of the Galilean satellite Europa and possibly Io and Ganymede but not Callisto.