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Traces of Magnetic Field in Jupiter’s Equatorial Ionosphere

Presentation #309.04 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Oral Presentation)

Published onOct 23, 2023
Traces of Magnetic Field in Jupiter’s Equatorial Ionosphere

Planetary ionospheres are the critical transition region between the magnetosphere and the underlying atmosphere, as these vast systems couple through this thin boundary layer at the top of the atmosphere. While there is relatively significant understanding of how these systems couple at Earth, the interactions at the Giant Planets are much more poorly understood.

Spectral analysis of near-infrared (NIR) emissions from the major upper-atmospheric ion, H3+, give us a unique window into this coupling at the Giant Planets. However, while we have detailed measurements of the thermospheric temperatures and ionospheric density within the auroral regions, mid-to-low latitudes have remained largely unexplored due to NIR emissions from these regions being much weaker and spectrally entangled with bright neutral species. Therefore, the interplay between the ionosphere and magnetic fields away from the poles remains enigmatic.

Previous long-term H3+ observations of Jupiter’s equatorial region, averaged over many nights, revealed large-scale features within the low-latitude ionosphere, originating from localised ionosphere-magnetosphere interactions. More recently, NASA’s Juno spacecraft has revealed great complexities in the Jovian magnetic field, with significant small-scale anomalies in sub-auroral regions, which appear to coincide with the complex structures detected in NIR ionospheric emissions.

Here, based on ground-based observations using the 10-meter Keck telescope in 2022, we present mid-to-low latitude maps of Jovian column-averaged H3+ temperatures, densities and radiance, capturing some of the previously identified ionospheric structures. Early indications from these observations show how brightness variations are driven by column density at Jupiter, as opposed to temperature, which suggests differences in ion population due to some as yet unknown destructive or productive process, driven by ionosphere-magnetosphere coupling.

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