Juno Plasma Wave Observations at Europa

• Published in: Geophysical research letters 2023-12, Vol.50 (24), p.n/a
• Main Authors: Kurth, W. S., Wilkinson, D. R., Hospodarsky, G. B., Santolík, O., Averkamp, T. F., Sulaiman, A. H., Menietti, J. D., Connerney, J. E. P., Allegrini, F., Mauk, B. H., Bolton, S. J.
• Format: Article
• Language: English
• Subjects: Atmospheric particulates; Charged particles; Density; Dust; Electric pulses; Electromagnetic fields; Electron beams; Electron density; Electrons; Equator; Europa; Flyby missions; Impulses; Jupiter; Jupiter probes; Magnetic equator; Magnetic field; magnetospheric interaction; Particle physics; Planetary magnetospheres; Plasma; Plasma density; Plasma waves; Solitary waves; Spacecraft
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL105775

Juno passed by Europa at an altitude of 355 km on 29 September, day 272, 2022. As one of Juno's in situ science instruments, the Waves instrument obtained observations of plasma waves that are essential contributors to Europa's interaction with its environment. Juno observed chorus, a band at the upper hybrid frequency providing the local plasma density, and electrostatic solitary structures in the wake. In addition, impulses due to micron‐sized dust impacts on Juno were recorded with a local maximum very close to Europa. The peak electron density near Europa was ∼330 cm−3 while the surrounding magnetospheric density was in the range of 50–150 cm−3. There was a significant separation between the Europa flyby and Juno's crossing of Jupiter's magnetic equator, enabling a unique identification of effects associated with the moon as opposed to magnetospheric phenomena normally occurring at the magnetic equator near 10 Jovian radii. Plain Language Summary Plasma waves are electromagnetic fields occurring in a plasma due to motions of the charged particles comprising the plasma. These waves can arise at various locations and at a range of frequencies depending on many factors, such as the number density of charged particles and the strength of the magnetic field. Here we discuss plasma waves observed by Juno during its 355‐km flyby of Europa on 29 September 2022. Some waves, called upper hybrid resonance emissions can provide information on the plasma density. Other waves, called electrostatic solitary waves are indicative of electron beams in the plasma. And yet other waves, called whistler‐mode chorus, are important in the interchange of energy between electrons and the waves, resulting in the acceleration of the electrons. Each of these types of waves were observed near Europa by the Juno plasma wave instrument and they are diagnostic of Europa's interaction with the Jovian magnetosphere. The Waves instrument also detects electrical impulses due to the collision of the spacecraft with dust grains moving at over 23 km/s that allow a determination of the concentration of dust near Europa. Key Points Two chorus bands, electrostatic solitary waves and upper hybrid emissions are observed at Europa Plasma densities near Europa derived from the upper hybrid resonance frequency peak near the wake axis at about 330 cm−3 Micron‐sized dust impacts peak near closest approach to Europa