Broadband electrostatic noise and field‐aligned currents in Jupiter's middle magnetosphere

Abstract

Voyager 1 plasma wave observations have revealed the presence of an impulsive electrostatic emission localized to the Jovian middle magnetosphere 10 <R <30 RJ that appears on the edges of the plasma sheet. This plasma mode has the same spectral and morphological characteristics of an emission that has been extensively studied in the earth's magnetosphere and has been associated with the presence of field‐aligned currents. We present the results of a detailed study of the properties of this Jovian emission by using comparisons with terrestrial observations as a basis for mode identification. The occurrence regions of the waves are compared with the measured magnetic field configuration to establish a correspondence with the plasma sheet. We then argue for a quasi‐permanent global system of field‐aligned currents linking the ionosphere of Jupiter to the middle magnetosphere, which powers energetic plasma heating processes occurring there. On the basis of knowledge of the consequences of field‐aligned currents in the terrestrial magnetosphere, we suggest a scenario for acceleration/precipitation of inverted V electrons concomitant aurorae, and energetic (∼10 keV) proton deposition into the middle magnetosphere resulting from field‐aligned potential drops associated with this current system.