Interchange instability is known to drive fast radial transport of particles in Jupiter's inner magnetosphere. Magnetic flux tubes associated with the interchange instability often coincide with changes in particle distributions and plasma waves, but further investigations are required to understand their detailed characteristics. We analyze representative interchange events observed by Juno, which exhibit intriguing features of particle distributions and plasma waves, including Z‐mode and whistler‐mode waves. These events occurred at an equatorial radial distance of ∼9 Jovian radii on the nightside, with Z‐mode waves observed at mid‐latitude and whistler‐mode waves near the equator. We calculate the linear growth rate of whistler‐mode and Z‐mode waves based on the observed plasma parameters and electron distributions and find that both waves can be locally generated within the interchanged flux tube. Our findings are important for understanding particle transport and generation of plasma waves in the magnetospheres of Jupiter and other planetary systems.
more »
« less
Statistical Survey of Interchange Events in the Jovian Magnetosphere Using Juno Observations
Abstract Interchange instability is known to drive fast radial transport of electrons and ions in Jupiter's inner and middle magnetosphere. In this study, we conduct a statistical survey to evaluate the properties of energetic particles and plasma waves during interchange events using Juno data from 2016 to 2023. We present representative examples of interchange events followed by a statistical analysis of the spatial distribution, duration and spatial extent. Our survey indicates that interchange instability is predominant atM‐shells from 6 to 26, peaking near 17 with an average duration of minutes and a correspondingM‐shell width of <∼0.05. During interchange events, the associated plasma waves, such as whistler‐mode, Z‐mode, and electron cyclotron harmonic waves exhibit a distinct preferential location. These findings provide valuable insights into particle transport and the source region of plasma waves in the Jovian magnetosphere, as well as in other magnetized planets within and beyond our solar system.
more »
« less
- Award ID(s):
- 2402179
- PAR ID:
- 10617698
- Publisher / Repository:
- Geophysical Research Letters
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 19
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Ultra-low-frequency (ULF) waves are known to modulate high-frequency whistler-mode waves within the Earth’s magnetosphere. Periodic bursts of whistler-mode waves are excited in association with ULF perturbations of plasma density and magnetic field. In this paper, we present a multievent study of whistler-mode waves modulated by ULF waves (0.05–1 Hz) observed by ARTEMIS in the vicinity of Earth’s Moon, when it was in the solar wind region upstream of the quasiparallel bow shock. The events exhibit periodic whistler-mode wave bursts between 0.2 and 0.4fce(electron gyrofrequency) coupled with ULF perturbations. Similar to modulation events observed within Earth’s magnetosphere, some of the strongest whistler-mode wave bursts were observed when electron density and magnetic field perturbations were anticorrelated. In one of the events, a strong positive correlation between electron density and magnetic field perturbations was observed during the excitation of whistler-mode waves. The ULF waves develop a periodic enhancement in transverse electron flux anisotropy, which is positively correlated with the whistler-mode wave bursts, thus providing conditions favorable for their generation. The observation of these events on the quasiparallel side of bow-shock suggests a possible connection between the observed ULF waves and the upstream waves in the Earth’s foreshock region. Finally, we examine the possibility that whistler-mode waves are trapped within localized regions of enhanced plasma density and magnetic field gradients produced by ULF waves in the solar wind.more » « less
-
Abstract We present statistical distributions of whistler‐mode chorus and hiss waves at frequencies ranging from the local proton gyrofrequency to the equatorial electron gyrofrequency (fce,eq) in Jupiter's magnetosphere based on Juno measurements. The chorus wave power spectral densities usually follow thefce,eqvariation with major wave power concentrated in the 0.05fce,eq–fce,eqfrequency range. The hiss wave frequencies are less dependent onfce,eqvariation than chorus with major power concentrated below 0.05fce,eq, showing a separation from chorus atM < 10. Our survey indicates that chorus waves are mainly observed at 5.5 < M < 13 from the magnetic equator to 20° latitude, consistent with local wave generation near the equator and damping effects. The hiss wave powers extend to 50° latitude, suggesting longer wave propagation paths without attenuation. Our survey also includes the whistler‐mode waves at high latitudes which may originate from the Io footprint, auroral hiss, or propagating hiss waves reflected to highMshells.more » « less
-
Abstract Magnetic flux integral quantities (e.g., flux tube entropy, flux tube content) are conserved quantities under the frozen‐in assumption. The change of these quantities often indicates the violation of the frozen‐in condition (e.g., interchange instability). In this study, we combine the Cassini CAPS and CHEMS moments data with a steady‐state magnetic field model (i.e., the Caudal model) to estimate the flux tube mass and flux tube entropy in Saturn's magnetosphere. Our statistical survey found that the flux tube mass rapidly decreases with radial distance away from Saturn in the inner magnetosphere and roughly levels out in the middle magnetosphere. This indicates that the radial transport processes could occur via a double‐reconnection process in the inner magnetosphere, while the radial transport processes appear to be more advective in the middle magnetosphere. Notice that Saturn's magnetosphere is stabilized by a radially increasing profile of flux tube entropy and destabilized by a radially decreasing profile of flux tube content. In this study, we also estimate the expected penetration location by using the flux tube interchange stability formalism developed by Southwood and Kivelson (1987,https://doi.org/10.1029/ja092ia01p00109). The results show that flux tube entropy can play a crucial role in braking the injections, while the flux tube content has a relatively smaller influence on the injected flux tube, being consistent with our previous case study by Wing et al. (2022,https://doi.org/10.3847/1538‐4357/ac85b2).more » « less
-
Abstract Previous statistical studies have described the distributions and properties of whistler‐mode waves in Jupiter's magnetosphere, but explaining these wave distributions requires modeling wave propagation from their generation near the magnetic equator. In this letter, we conduct ray tracing of whistler‐mode waves based on realistic Jovian magnetic field and density models. The ray tracing results generally agree with the statistical wave distributions based on Juno measurements. The modeled ray paths show that high‐frequency waves generated near the equator are confined within 20° magnetic latitude due to Landau damping, low‐frequency waves can propagate to higher latitudes and lowerM‐shells, with changing wave normal angles, and a portion of low‐frequency waves could propagate to highMshells at high latitudes. Our modeling results provide a theoretical interpretation of whistler‐mode wave distributions and properties, providing essential insights for future radiation belt models at Jupiter.more » « less
An official website of the United States government

