,,- University of Bristol, University of Bristol, Faculty of Science and Engineering, BRISTOL, United Kingdom of Great Britain – England, Scotland, Wales (uy18846@bristol.ac.uk)
Uranus is an Ice Giant planet, a class of large, cold planets characterized by thick atmospheres and the absence of a well-defined solid surface. Hence, atmospheric processes are fundamental to understanding the planet’s physical and chemical environment. Atmospheric ionisation on Earth is driven by solar radiation and energetic particles, radioactive gases and Galactic Cosmic Rays (GCRs) [1]. GCR-induced ionisation is believed to be dominant on Uranus due to its distance from the Sun. In this work, we model the GCR air showers using CORSIKA8 Monte Carlo simulations [2] and calculate the vertical ionisation rate. We capture the variation of ionisation rates with geomagnetic latitude in a novel global map and, for the first time, present a quantitative comparison with ionospheric ionisation rates derived from parameters adopted from the literature. The results show GCR-induced ionisation in the lower stratosphere (peaking at ~104 Pa) to be around two orders of magnitude larger than ionospheric ionisation (<10-1 Pa), highlighting the significance of GCRs in Uranus’s atmosphere and raising questions about potential seasonal variability associated with solar-driven ionospheric processes.
The conditions in the lower stratosphere were carefully constrained, and with appropriate assumptions regarding steady-state conditions and dominant recombination mechanisms, the ion balance equation was solved to estimate the positive ion and electron number densities. Ion and electron densities peak at approximately the same altitude as the peak of GCR-induced ionisation with an upper limit of ~2×109 ions m-3 in the absence of aerosols, while the inclusion of aerosols leads to a difference between positive ion (~109 ions m-3) and electron densities (~108 electrons m-3). The electrical characteristics as well as cloud microphysics assumptions allow investigation of the possibility and nature of lightning activity expected on Uranus.
[1] Hillas, A. M. (1972). Cosmic rays (1st ed.). New York: Oxford ; New York : Pergamon Press.
[2] Gottowik, M. (2025). Corsika 8: A modern and universal framework for particle cascade simulations. arXiv preprint arXiv:2508.08755.
How to cite: Al-Khuraybi, O., Aplin, K., and Gambaruto, A.: Characterising Uranus’ Ionisation and Conductivity Profile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15467, https://doi.org/10.5194/egusphere-egu26-15467, 2026.
