Understanding the relationship between the size variations of Jupiter’s magnetosphere, auroral brightness and solar wind pressure using Juno observations

The size of Jupiter’s magnetosphere and the total power emitted by the planet’s auroras both vary considerably with time. Two potential drivers of this variability are the upstream solar wind conditions and the internally-driven mass loading/unloading of the magnetosphere, but the relative contributions of these external and internal mechanisms are not clear. In this work, we present ongoing work which uses data from multiple instruments on the Juno spacecraft to investigate the relationship between the location
of the magnetopause, the brightness of the auroras and the dynamic pressure of the solar wind. Four in-situ instruments on Juno (JADE, JEDI, MAG and Waves) are able to detect magnetopause crossings during the apojove period of the spacecraft’s orbit. Over the eight years of the mission there has been significant evolution in the orbital geometry, which means that a large segment of three-dimensional space has now been probed. We use the entire Juno trajectory thus far to fit a parameterized surface representing the
magnetopause in its most expanded state. For each detected magnetopause crossing, we then compare the spacecraft position with this fitted surface to quantify the level of compression that the magnetosphere was experiencing. These results will be compared with simultaneous measurements of the total auroral power obtained by the Juno UVS instrument and with solar wind model predictions. The presence or absence of any correlations between these three datasets will help us to build a more cohesive picture of how different elements of Jupiter’s magnetosphere interact with one another.