Magnetotail structure of the giant magnetospheres: Implications of the viscous interaction with the solar wind

Abstract

The internal sources of plasma in the giant magnetospheres of Jupiter and Saturn affect magnetospheric dynamics in terms of magnetosphere‐ionosphere coupling and auroral current systems, as well as the interaction with the solar wind. The radial transport of plasma at Jupiter is well constrained to vary between 300 kg/s and 1200 kg/s over timescales of 20–60 days. Saturn's neutral‐dominated inner magnetosphere has presented a challenge for determining the radial mass transport rates with values ranging between 20 kg/s and 280 kg/s over timescales of 20–80 days. We present an estimate of the radial mass transport rates associated with magnetospheric plasma production for Jupiter and Saturn, assuming that magnetospheric plasma loss (equal to the plasma source) can be treated as mass pickup by the solar wind. That is, the magnetospheric plasma is assumed to be at rest with respect to the solar wind, analogous to cometary mass loading of the solar wind flow. This Alfvénic coupling between the solar wind and the magnetosphere suggests mass loading rates of 500–1500 kg/s for Jupiter and 20–50 kg/s for Saturn, consistent with observations and physical chemistry models. We discuss implications for magnetotail structure by considering the contribution of the viscous interaction of the solar wind with the giant magnetospheres. We suggest that a significant portion of the magnetotail structure can be attributed to this viscous interaction.