Solar wind pressure effects on Jupiter decametric radio emissions independent of Io

Abstract

This paper investigates the effects of the solar wind dynamic pressure on Jupiter auroral radio emissions at decametric wavelengths that are not controlled by the electrodynamic interaction with the moon Io (non-Io DAM). In order to conduct this study, Nançay decametric array radio data are analyzed for the 1996–1999 period. Solar wind conditions at Jupiter's orbit are studied using the Michigan University solar wind propagation model (mSWiM). Interplanetary fast shocks (forward shocks, FS, or reverse shocks, RS), and average solar wind dynamic pressure are correlated with non-Io DAM emission occurrence, duration and power. It is found that non-Io DAM emissions occur preferentially during periods of enhanced solar wind dynamic pressure and after a FS or a RS arrival at Jupiter. The dawn (non-Io B-type) and dusk (non-Io-A-type) radio emissions are investigated separately and show (1) a dawn-dusk asymmetry consistent with prior studies and auroral ultraviolet (UV) observations, and (2) different behaviors in response to solar wind shocks. Our study confirms the solar wind control of – at least a part of – the non-Io DAM, and refines the scenario of response of the radio emissions to the solar wind interaction with the Jovian magnetosphere.