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In-situ exploration of the moon-magnetosphere interactions in the Jovian system: a comparative study based on high-latitude Juno measurements

Presentation #324.04 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Poster)

Published onOct 23, 2023
In-situ exploration of the moon-magnetosphere interactions in the Jovian system: a comparative study based on high-latitude Juno measurements

Moon-magnetosphere interactions result from the encounter between a magnetospheric plasma flow and moons, which act as obstacles to the plasma flow. In the Jovian magnetosphere, the Galilean moons orbit with a Keplerian velocity much slower than the plasma velocity, driven in near corotation by the planetary magnetic field. Therefore, they disturb the magnetospheric plasma flow, which in turn generates Alfvén waves in their close environments. These waves propagate along the magnetic field, accelerating particles and triggering auroral emissions in the giant planet atmosphere.

Since August 2016, the Juno mission has made it possible to characterize in-situ the moon-magnetosphere interactions. Several crossings at high latitude of flux tubes connected to the orbits of the Galilean moons have been reported revealing a diversity of particles and waves properties, reflecting the underlying acceleration processes.

In this communication, we present the first comparative study of electron properties measured within the flux tubes of Io, Europa and Ganymede. We show that, for all the three moons, the precipitating electron energy fluxes decrease exponentially downstream of the moons according to a metric that takes into account the path of Alfvén waves. The e-folding values, characterizing the decay rate, reflect the amplitude of the interactions between the moons and Jupiter’s magnetosphere. These correlate well with the decay in UV brightness of the auroral tails observed at Jupiter’s pole.

Finally, we show that two types of electron energy distributions exist for Europa and Ganymede, depending on the distance from the moon. Conversely, only broadband spectra have so far been observed in Io’s flux tubes.

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