Fig. 1
Schematic view of the Jovian magnetosphere. The magnetosphere is the cavity in the solar wind (SW) created by the Jovian magnetic field and is stretched antisunward. The aurora is manifested by increasing energetic (energy of 100–300 keV) electron precipitation along the magnetic field line to Jupiter’s polar atmosphere from the middle/outer magnetosphere (time = t 1). Inward transport of hot electrons (energy of 10–100 s of electron volts, presumed to come from the middle magnetosphere together with energetic electrons) to the inner part of the magnetosphere causes torus brightening (time = t 2). An issue addressed for years is the energy source that sustains the intense radiation of the IPT. The hot electron transport from the distant region is one candidate. If the position of high-energy electron emergence in the middle/outer magnetosphere does not greatly change, the travel time (t 2 − t 1) represents the average inward velocity between the two regions