Morphology of the Io Plasma Torus From Juno Radio Occultations

Moirano, Alessandro; Casajus, Luis Gomez; Zannoni, Marco; Durante, Daniele; Tortora, Paolo

doi:10.1029/2021ja029190

Cited by 11 publications

(23 citation statements)

References 66 publications

(211 reference statements)

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“…The electron density reported in the present study is between <2,000 cm −3 and 2,750 cm −3 , in agreement with the results from the radio occultations. More specifically, the radio occultation during PJ 11 showed a remarkably low electron density compared to other orbits, while the torus appeared slightly thicker (Moirano, Gomez Casajus, et al., 2021; Phipps et al., 2021). This suggests that the position of the IFP of PJ 11 in panel b of Figure 4 may be explained by a density depletion rather than a temperature drop.…”

Section: Discussionmentioning

confidence: 94%

Variability of the Auroral Footprint of Io Detected by Juno‐JIRAM and Modeling of the Io Plasma Torus

et al. 2023

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One of the auroral features of Jupiter is the emission associated with the orbital motion of its moon Io. The relative velocity between Io and the surrounding plasma trigger perturbations that travels as Alfvén waves along the magnetic field lines towards the Jovian ionosphere. These waves can accelerate electrons into the atmosphere and ultimately produce an auroral emission, called the Io footprint. The speed of the Alfvén waves ‐ and hence the position of the footprint ‐ depends on the magnetic field and on the plasma distribution along the field line passing through Io, whose SO2‐rich atmosphere is the source of a dense plasma torus around Jupiter. Since 2016, the Jovian InfraRed Auroral Mapper (JIRAM) onboard Juno has been observing the Io footprint with a spatial resolution of ∼ few tens of km/pixel. JIRAM detected evidences of variability in the Io footprint position that are not dependent on the System III longitude of Io. The position of the Io footprint in the JIRAM images is compared with the position predicted by a model of the Io Plasma Torus and of the magnetic field. This is the first attempt to retrieve quantitative information on the variability of the torus by looking at the Io footprint. The results are consistent with previous observations of the density and temperature of the Io Plasma Torus. However, we found that the plasma density and temperature exhibit considerable non‐System III variability that can be due either to local time asymmetry of the torus or to its temporal variability.This article is protected by copyright. All rights reserved.

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Section: Discussionmentioning

confidence: 94%

Variability of the Auroral Footprint of Io Detected by Juno‐JIRAM and Modeling of the Io Plasma Torus

et al. 2023

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“…In addition, beams of electrons propagate along field lines leading to Transhemispheric Electron Beam (TEB) spots (Bonfond et al., 2008). Juno observations have confirmed the Alfvénic wave power associated with the satellite footprints (Gershman et al., 2019; Moirano, Gomaz Casajus et al., 2021; Moirano, Mura et al., 2021; Sulaiman et al., 2020; Szalay et al., 2020). Szalay et al.…”

Section: Introductionmentioning

confidence: 87%

“…(2018) also suggested that the plasma torus radial distribution from 6 to 8 R J takes ∼15 days from the beginning of eruption (Yoneda et al., 2015). As a result, the connection between the volcanic eruptions on Io and the variations in the plasma environment in Jupiter's magnetosphere is highly complex (Moirano, Gomaz Casajus et al., 2021; Moirano, Mura et al., 2021; Roth et al., 2020). In addition, Kita et al.…”

Section: Introductionmentioning

confidence: 99%

Ganymede's Auroral Footprint Latitude: Comparison With Magnetodisc Model

et al. 2022

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Variations of Ganymede's auroral footprint locations are presented based on observations by the Hubble Space Telescope in 2007 and 2016. The poleward and equatorward shifts of Ganymede's footprint could be influenced by the mass outflow rate from Io and the solar wind compression, as the internal and external factors respectively. We compare our results with Ganymede's footprint mapping based on the magnetodisc model. The mapped footprint in Jupiter's ionosphere shifts equatorward with increased hot plasma parameter, Kh, which is associated with hot plasma pressure. We analyzed the effect of cold plasma number density (Nc), related to the mass outflow rate and connected to the material produced by Io. The results show that the magnetic footprint is shifted equatorward by 0.37° when the mass outflow rate is increased from 800–2,000 kg s−1. Iogenic plasma has a strong influence on the stretching of the magnetic field lines in Jupiter's middle magnetosphere, causing the equatorward shift of Ganymede's footprint. For external factors, Ganymede's footprint shifted poleward by 0.62° under the influence of solar wind compression while the mass outflow is kept constant at 1,000 kg s−1. We present similar locations of Ganymede's footprint based on the field lines mapped as a result of the compensation between an increase of Kh and the solar wind compression. Overall, the location of Ganymede's auroral footprint corresponds with the mass loading rate from Io and the solar wind dynamic pressure.

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“…The data were weighted on a pass-by-pass basis using the root mean square of the residuals. Additionally, G29 data were de-weighted to take into account possible Io Plasma Torus (e.g., Bagenal, 1994;Moirano et al, 2021) calibration errors. Finally, the one-way passes were de-weighted by a factor of 2, to take into account the poorer stability of the non-coherent link.…”

Section: Observation Geometry and Datamentioning

confidence: 99%

The gravity field of Ganymede after the Juno Extended Mission

Casajus¹,

Zannoni²,

Tortora³

et al. 2024

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The Juno Extended Mission (EM) comprises additional orbits, during which Juno will continue its observations of the Jupiter system. Juno's highly elliptic and almost polar trajectory exploits Jupiter's oblateness perturbation to precess the periapsis of the orbit northward, allowing Juno to cross the satellite orbital plane during the inbound trajec tory at closer distances from Jupiter during each revolution (Hansen et al., 2022). This trajectory design allowed the inclusion of 4 close encounters of the inner Galilean satellites, 1 of Ganymede, 1 of Europa and 2 of Io.The EM trajectory started diverging from the nominal trajectory after the 32nd perijove pass (PJ32), in order to enable the first Ganymede's flyby (hereafter referred to as G34, because it occurred just before the 34th perijove pass). On 7 June 2021, Juno successfully performed the close encounter with Ganymede with a closest approach altitude of 1,045 km and a relative velocity of 18.5 km/s. During the flyby, a coherent two-way radio link between Juno and the antennas of the Deep Space Network (DSN) was maintained, allowing to perform a radio occultation experiment, which detected a high electron density peak during the ingress occultation consistent with an ionosphere (Buccino et al., 2022). Moreover, Doppler shift measurements were acquired, offering the opportunity to update Ganymede's gravity field for the first time since the end of the Galileo mission.

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Morphology of the Io Plasma Torus From Juno Radio Occultations

Cited by 11 publications

References 66 publications

Variability of the Auroral Footprint of Io Detected by Juno‐JIRAM and Modeling of the Io Plasma Torus

Variability of the Auroral Footprint of Io Detected by Juno‐JIRAM and Modeling of the Io Plasma Torus

Ganymede's Auroral Footprint Latitude: Comparison With Magnetodisc Model

The gravity field of Ganymede after the Juno Extended Mission

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