Evidence for Magnetic Reconnection at Ganymede's Upstream Magnetopause During the PJ34 Juno Flyby

Self Cite

Most of what is known from the interaction of Ganymede with Jupiter's magnetosphere originates from six Galileo close flybys (ranging from 264.4 to 3,104.9 km in altitude) (e.g., Kivelson et al., 2022).Approaching its 34th perijove, Juno came as close as 1,046 km from Ganymede's surface (sub-spacecraft latitude of 23.6°N) on 7 June 2021 (Hansen et al., 2022). Juno approached Ganymede from southern latitudes, passed through a part of the wake region that was unexplored by previous missions, through its magnetosphere to closest approach on the night side, then to the dayside, and went back into the plasma disk toward Jupiter. Highlights of the flyby from Juno's suite of instruments are reported in this issue.In this paper, we summarize plasma observations made by the Jovian Auroral Distributions Experiment (McComas et al., 2017). JADE consists of two electron (JADE-E) and one ion (JADE-I) sensors. JADE-E are top-hat analyzers measuring 0.032-32 keV electron distributions at 1 s time resolution. JADE-I has a top-hat analyzer and a time-of-flight (TOF) section to determine ion energy-per-charge (E/q) and mass-per-charge (m/q)

Section: Between D and E -Magnetopause Boundary Layersupporting

confidence: 82%

“…There is also evidence for magnetic reconnection in this region (Ebert et al., 2022 and Romanelli et al., 2022).…”

Section: Ion and Electron Overviewmentioning

confidence: 91%

See 1 more Smart Citation

Plasma Observations During the 7 June 2021 Ganymede Flyby From the Jovian Auroral Distributions Experiment (JADE) on Juno

Allegrini

Bagenal

Ebert

et al. 2022

Self Cite

“…Romanelli et al (2022) andEbert et al (2022) argue that evidence for reconnection in the extended upstream magnetopause is observed by Juno and the ESWs observed by Waves (see examples in FigureS5in Supporting Information S1) supports this.…”

mentioning

confidence: 80%

Juno Plasma Wave Observations at Ganymede

Kurth

Sulaiman

Hospodarsky

et al. 2022

Self Cite

Just prior to the end of its prime mission, Juno flew by Ganymede (Hansen et al., 2022). The flyby takes advantage of Juno's advanced instrument complement to study details of the plasma, energetic particles and fields involved in the interaction between Ganymede's and Jupiter's magnetospheres. This paper focuses on plasma waves in Ganymede's magnetosphere.Galileo plasma wave and magnetic field measurements revealed the existence of Ganymede's magnetosphere during its first flyby of the moon (Gurnett et al., 1996;Kivelson et al., 1996). Additional Galileo studies included six close flybys (Shprits et al., 2018). The plasma wave observations showed a variety of emissions commonly associated with planetary magnetospheres, including whistler-mode emissions, electron cyclotron harmonics, a band at the upper hybrid frequency, broadband noise bursts at the magnetopause, and even radio emissions emanating from the moon's magnetosphere (Gurnett et al., 1996;Kurth et al., 1997).The Juno spacecraft executed a close flyby of Ganymede at 16:56 on 7 June, day 158, 2021 with a closest approach altitude of 1046 km. The trajectory approached Ganymede over its leading hemisphere or downstream from the moon relative to the co-rotational flow of Jupiter's magnetospheric plasma. The trajectory projected into the z-x and y-x planes is shown in Figure 1 using Ganymede-centered co-rotational coordinates (sometimes referred to as G PhiO ). The +z axis is parallel to Jupiter's rotational axis and the +x axis is parallel to the nominal co-rotational plasma flow. The +y axis is in the direction of Jupiter. The radius of Ganymede (R G ) is 2,631.2 km. The blue, green, and red bars denoted with the numbers 1, 2, and 3 identify regions observed in Ganymede's magnetosphere and will be used to organize the discussion of the Waves observations.

“…Additionally, another aspect that makes Ganymede particularly interesting is the phenomenon of magnetic reconnection. Unlike Earth, and other planetary magnetospheric environments, which are embedded in dynamic solar wind conditions, the upstream conditions near Ganymede are relatively steady compared to plasma convection through Ganymede's magnetospheric system (Kivelson et al., 1998), therefore, making it possible to probe the nature of magnetic reconnection under relatively steady driving conditions (Ebert et al., 2022; Jia et al., 2010; Romanelli et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Energetic Charged Particle Observations During Juno's Close Flyby of Ganymede

Clark

Kollmann

Mauk

et al. 2022

Self Cite

Ganymede-Jupiter's largest moon-is the only known moon in the Solar System to generate its own internal magnetic field (Gurnett et al., 1996;Kivelson et al., 1996) and therefore its space environment is of high scientific interest. In part, what makes Ganymede so interesting is that its magnetic field forms a mini-magnetosphere, with field lines connected to both hemispheres, that is, "closed," embedded deep within (semi-major axis = 14.97 Jovian radii or R J ) Jupiter's magnetosphere where the Alfvénic Mach number (M A ) is < 1. Classified as a sub-Alfvénic (and thus also sub-fast-magnetosonic by definition) interaction (e.g., Saur, 2021), no bow shock develops around the moon. Additionally, another aspect that makes Ganymede particularly interesting is the phenomenon of magnetic reconnection. Unlike Earth, and other planetary magnetospheric environments, which are embedded in dynamic solar wind conditions, the upstream conditions near Ganymede are relatively steady compared to plasma convection through Ganymede's magnetospheric system (Kivelson et al., 1998), therefore, making it possible to probe the nature of magnetic reconnection under relatively steady driving conditions (Ebert