Bimodal size of Jupiter's magnetosphere

Observations of Jovian magnetopause crossing by a number of different spacecraft have established that Jupiter's magnetosphere has a generally bimodal size distribution, with typical standoff distances at the nose of similar to 63 and similar to 92 R-J. Here we examine both the external solar wind structure and time constants and the internal magnetospheric time constants for shedding and refilling material in the Jovian plasma disk. We show that these latter time constants are similar to hours to similar to 10 h, comparable to the compression time of the magnetopause, but shorter than the typically several day expansion time when the solar wind dynamic pressure decreases. Together, we show that it is the well-developed compressions and rarefactions in the solar wind at similar to 5 AU that produced the generally bimodally structured solar wind dynamic pressure and hence Jovian magnetospheric size.