Jupiter’s Stable Upper Atmosphere: Mapping Long-term Temperature Trends and Ionospheric Density Structures

We present global temperature and density maps of Jupiter’s upper atmosphere from 15 nights of observation on Keck/NIRSPEC across 2022-2025 in support of the Juno mission. On average, each night provides ~12,000 pole-to-pole, L-band spectra over approximately 100 degrees of longitude. Within these spectra are emissions from the dominant molecular ion, H₃⁺, which yield column-averaged temperatures and column-integrated densities at local noon. We find a median equatorial temperature of 760 ± 75 K, with night-to-night variation up to 130 K over a year. Temperatures decrease monotonically from pole to equator, consistent with the aurora being the primary source of heating at low latitudes. Mean auroral temperatures are approximately equal in the north and south, 1100  ± 100 K, and are far more variable—up to 300 K on long timespans. Our density map reveals the same highly structured features as presented in the Stallard et al. H₃⁺ global emission map, proving this depleted emission is caused by low density regions of the upper atmosphere. Additionally, it highlights the permanence of these structures in Jupiter’s upper atmosphere due to their persistence for nearly 30 years.  

 

Long thought to be a highly variable system, we present the highest spatial resolution, first global, and first multi-epoch maps of Jupiter’s upper atmosphere which reveal morphologies that are remarkably consistent over year- to decades-long timespans. With our maps we contribute further evidence of the magnetosphere-ionosphere control seen in previous H₃⁺ emission maps, and tie their features to longstanding magnetically-controlled density variations. Observed pole-to-pole temperature structure is consistent in time and attributed to the redistribution of auroral energy.

 

 

Stallard, T. S. et al. (2018). Identification of Jupiter’s magnetic equator through H₃⁺ ionospheric emission. NatAs 2018 2:10, 2(10), 773–777. https://doi.org/10.1038/s41550-018-0523-z

**This material is based upon work supported by Future Investigators in NASA Earth, Space Science, and Technology Grant 80NSSC23K1637 and Keck Key Strategic Mission Support Grants 80NSSC22K095 and 80NSSC25K7727.