A theory of Jovian dekametric emission

Many Jovian dekametric storms, like terrestrial magnetic storms, commence suddenly, not just as seen from the Earth, but in real time. ‘Main Rotation phase’ storm commencements rarely occur before Jupiter's Northern Hemisphere magnetic pole crosses the central meridian, but occur abundantly immediately thereafter. ‘Early Io phase’ storm commencements occur increasingly abundantly as Io approaches phase 100°, but only rarely thereafter.In explanation of Main Rotation storms, this paper proposes that, as Jupiter's eccentric northern hemisphere magnetic pole crosses the heliocentric central meridian, Jupiter's magnetic tail swings abruptly from Jupiter's morning to afternoon side. It ascribes Early and Late Io storms respectively to the emergence and re-entry of Io through the sunward boundary of the Jovian magnetosphere.