Speaker
Description
The plasma torus at Io’s orbit has been shown to be a locus of intense Alfvén and ion cyclotron waves, which are trapped in the region by the waveguide properties of the torus. Research featuring these waves has progressed towards a detailed understanding of temporal variability in the region, which is vital to the upcoming JUICE mission’s aim to characterise the Galilean moons. Here we show that this understanding may be incomplete: an additional population appears to be present in the region, consisting of ultra-low-frequency magnetohydrodynamic waves.
We have used magnetometer data from the Galileo spacecraft to identify intervals of large-amplitude ultra-low-frequency wave activity in the vicinity of the plasma tori. We show how the characteristics of these waves inside the torus is distinct from elsewhere in the magnetosphere, and that the waves may be driven by processes both internal and external to the torus.
We demonstrate that the plasma torus at Io’s orbit—and perhaps the torus at Europa’s orbit—may act as a localized resonator, absorbing ultra-low-frequency waves from the larger magnetosphere, and thereby potentially acting as a reservoir of energy introduced by perturbations system-wide.
