Magnetospheric Interactions of Saturn's Moon Dione (2005–2015)

Abstract

The moon Dione orbits Saturn at 6.2 Saturn radii R S deep in the Kronian magnetosphere. In situ studies of the moon-magnetosphere interaction processes near Dione were possible with the Cassini/Huygens mission which flew by close to Dione five times at distances between 99 and 516 km. In addition, Cassini crossed Dione's L-shell more than 400 times between 2004 and 2017 and documented the variability of Saturn's magnetosphere. Different flyby geometries allowed to study the interaction processes upstream, in the low-energy wake, and above the north pole of Dione. We describe here the energetic particle measurements from the Low Energy Magnetospheric Measurement System (LEMMS), part of the Magnetosphere Imaging Instrument (MIMI) onboard Cassini. We also use hybrid simulation results from "A.I.K.E.F." to interpret the signatures in the particle fluxes. This paper is a continuation of Krupp et al.

Investigating the Moon's Interaction With the Terrestrial Magnetotail Lobe Plasma

“…To maintain pressure balance within this density cavity, the wakeside magnetic field is compressed, manifesting as an enhanced signature of δB x confined to a cylinder ∼2R L wide (figure 2(d)). Similar pressure balance features appear in the extended lunar wake when located in the solar wind (e.g., Fatemi et al, 2012;Halekas et al, 2005;Travnicek et al, 2005), and near moons in the outer solar system including Rhea and Dione (e.g., Khurana et al, 2017;Krupp et al, 2020;Roussos et al, 2008;Simon et al, 2012Simon et al, , 2011. The pickup ion populations of these Saturnian moons are so dilute that they are unable to compensate the reduced pressure caused by absorption of the magnetospheric plasma.…”

Variability in the Energetic Electron Bombardment of Ganymede

“…For this reason, we import the electromagnetic fields calculated by the hybrid model into the Galilean Energetics Tracing Model (GENTOo; Liuzzo et al, 2019b) to study energetic electrons near Ganymede. Similar techniques of combining output of a hybrid model with a test particle simulation have been used to study energetic ion and electron dynamics at various Jovian moons including Ganymede (Fatemi et al, 2016;Poppe et al, 2018), Callisto (Liuzzo et al, 2018(Liuzzo et al, , 2019a(Liuzzo et al, , 2019b, and Europa (Arnold et al, 2019(Arnold et al, , 2020Breer et al, 2019), as well as multiple moons of Saturn (e.g., Feyerabend et al, 2015;Kotova et al, 2015;Krupp et al, 2020;Regoli et al, 2016).…”

Role of the Ionospheric Conductance Profile in Sub‐Alfvénic Moon‐Magnetosphere Interactions: An Analytical Model

“…At Europa, Ganymede, and Callisto the resulting ionosphere‐magnetosphere interaction is modified to a varying degree by permanent or induced magnetic moments from the objects’ interiors and ionospheres (e.g., Hartkorn & Saur, 2017; Kivelson et al., 1999, 2002; Liuzzo et al., 2016; Zimmer et al., 2000). The neutral gas envelopes of, for example, Saturn's icy moons Tethys, Dione, and Rhea are so dilute that newly produced ions can be treated as test particles and the observed magnetic field perturbations arise almost exclusively from absorption of the impinging magnetospheric flow at the moons’ surfaces (e.g., Krupp et al., 2020; Roussos et al., 2008; Simon et al., 2009; Simon, Saur, Kriegel, et al., 2011; Simon, Saur, Neubauer, et al., 2011). If the combination of ambient magnetic field strength, upstream plasma density and temperature is favorable, such an absorption‐driven interaction alone may still generate weak Alfvén wings, as observed by the Cassini spacecraft at Rhea (Khurana et al., 2017; Simon et al., 2012).…”