Journal article
Auroral Ionospheric Erosion at Jupiter
Journal of geophysical research. Space physics, Vol.130(8), e2025JA034156
08/2025
DOI: 10.1029/2025JA034156
Abstract
The generation of Jupiter's main auroral oval is dominated by broadband‐energy electron beams, in contrast with the dominance of peaked electron energy spectra at Earth. Wave‐particle interactions involving Alfvén waves have been theorized to be the main mechanism driving the broadband acceleration of electrons. Alfvénic interactions are favored in the presence of density depletions and steep density gradients across adjacent magnetic field lines. Here we present electron densities at low altitudes (0.3–2.8 ) above the diffuse and main auroras inferred from frequency cutoffs in plasma wave spectra measured by the Juno/Waves instrument during the first 62 perijoves. We find that the electron densities above the diffuse and main auroras consistently decrease toward poleward latitudes and can be depleted down to the order of . Moreover, we show that the spatial gradient of the density depletion varies with altitude, and the peak in the density gradient occurs above 1 , suggesting altitudes at which Alfvénic acceleration is most likely. Finally, we find that these auroral density gradients are much steeper than are found in the non‐auroral ionosphere, indicating an active cavitation process connected with the aurora likely driven by the action of Alfvén waves.
Recent measurements in Jupiter's auroral regions by the Juno spacecraft reveal stark distinctions from Earth's auroras. The electrons that impact the atmosphere to generate the aurora were observed to possess broadband energy spectra, rather than the peaked spectra that were expected. The broadband acceleration has been proposed to come from interactions with Alfvén waves, a type of electromagnetic wave within the plasma, which strongly depend on the density of the plasma. In this paper, we present an analysis of plasma density data inferred from the plasma wave instrument on the Juno spacecraft. We find that the electron densities above the auroras consistently decrease toward poleward latitudes down to heavily depleted densities, which favors acceleration by Alfvén waves. Additionally, the spatial gradient of this density decrease is larger above an altitude of 1 Jovian radius, providing a constraint for the range of altitudes at which the acceleration is most likely to occur. Finally, we demonstrate a clear distinction between the steep density depletions in the auroral regions from the non‐auroral ionosphere, which points toward a process associated with the aurora that keeps the density depleted.
We present electron densities at low altitudes above Jupiter's main aurora that are persistently depleted toward poleward latitudes Steep spatial gradients of the depletions above 1 suggest a more preferential plasma environment for Alfvénic acceleration Steeper gradients than in the non‐auroral ionosphere suggest ionospheric erosion by Alfvén waves connected with the main aurora
Details
- Title: Subtitle
- Auroral Ionospheric Erosion at Jupiter
- Creators
- N. S. Kruegler - University of MinnesotaA. H. Sulaiman - University of MinnesotaS. S. Elliott - University of MinnesotaW. S. Kurth - University of IowaR. L. Lysak - University of MinnesotaS. J. Bolton - Southwest Research Institute
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.130(8), e2025JA034156
- DOI
- 10.1029/2025JA034156
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Publisher
- AMER GEOPHYSICAL UNION
- Grant note
- National Aeronautics and Space Administration: 80NSSC20K1269 NASA: AGS-2225270 NSFRoy J. Carver Charitable Trust
The research at the University of Minnesota is partly supported by NASA through contract S99022AKP with the Southwest Research Institute. NSK and AHS acknowledge NASA Grant 80NSSC24K1837. The research at the University of Iowa is supported by NASA through Contract 699041X with the Southwest Research Institute. RLL acknowledges NASA Grant 80NSSC20K1269 and NSF Grant AGS-2225270. The authors acknowledge the use of the Space Physics Data Repository at the University of Iowa supported by the Roy J. Carver Charitable Trust. The authors would also like to acknowledge Masafumi Imai for his magnetic field line and ionospheric footprint data sets; Jeremy Faden, Chris Piker, and Darrelle Wilkinson for their support with Autoplot and the Juno/Waves data products; and Elsa Mead for discussions of the error associated with digitization of the O-mode.
- Language
- English
- Date published
- 08/2025
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984948004302771
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