MIST
Magnetosphere, Ionosphere and Solar-Terrestrial
The Non-Linear Dependence of Daily Maximum Ionospheric Total Electron Content on F10.7
The Non-Linear Dependence of Daily Maximum Ionospheric Total Electron Content on F10.7
By Martin Cafolla (University of Warwick)
Solar Extreme Ultraviolet (EUV) radiation drives ionisation in the upper atmosphere to create the ionosphere. The variability of the intensity of this radiation results in regions of high electron number density across the ionosphere, characterised by the Total Electron Content (TEC). The daily solar flux at 10.7cm, the F10.7 index, is commonly used as a proxy to EUV in ionospheric models. Typically studies have shown how either the global averages or geographically local values of TEC vary with daily F10.7, F10.7A (the 81-day average) and F10.7p (a combination of daily F10.7 and F10.7A). We study how the daily maximum TEC correlates with daily F10.7 using 15-minute Global Ionospheric Maps (GIMs) from the Jet Propulsion Laboratory (JPL) between 2003-2024.
We find that for F10.7 ≳ 78 − 85 SFU, the daily maximum TEC saturates to a seasonally dependent value between 83−128 TECU. We asses the distribution of the residuals from linear and non-linear least squares fitting as a function of F10.7, as demonstrated in the figure below, and find that a tanh function out-performs a linear function for F10.7 ≥ 150 SFU. Our results are sensitive to different hemispheres, as a result of the construction of JPL-GIMs. Finally, we find that the daily F10.7 clearly resolves the saturation of daily maximum TEC, while F10.7 based on the average does not. Quantifying the value at which the daily maximum TEC saturates with F10.7, and its seasonal dependence, specifies the requirements of systems that are sensitive to extremes in TEC, important in planning of Low Earth Orbit satellite operations.
See publication for more details:
Cafolla, M. A., Chapman, S. C., Watkins, N. W., & Verkhoglyadova, O. P. (2026). The non-linear dependence of daily maximum ionospheric total electron content on F10.7. Space Weather, 24, e2025SW004745. https://doi.org/10.1029/2025SW004745
JWST Discovers the Vertical Structure of Uranus' Ionosphere
JWST Discovers the Vertical Structure of Uranus' Ionosphere
By Paola I. Tiranti (Northumbria University, School of Engineering, Physics and Mathematics, Newcastle, UK.)
Uranus’s upper atmosphere is one of the least understood in our Solar System, despite being critical for understanding how giant planets interact with their space environment. Using the James Webb Space Telescope, we observed Uranus for a full rotation and measured the vertical structure of its ionosphere - the charged layer of the atmosphere where aurorae form. Our results show that temperatures peak around 3,000 - 4,000 km above the planet, while ion densities peak near 1,000 km, and are significantly weaker than predicted by models. We also find two bright bands of auroral emission close to Uranus’ magnetic poles, as well as a surprising region where both emission and density are depleted, likely linked to the unusual geometry of Uranus’ tilted and offset magnetic field. These discoveries not only confirm that Uranus’ upper atmosphere has been cooling for decades, but also reveal new structures shaped by its magnetic environment. Together, they provide critical benchmarks for future missions and improve our understanding of how giant planets (both in our Solar System and beyond) balance energy in their upper atmospheres.
See publication for more details:
Tiranti, P. I., Melin, H., Moore, L., Thomas, E. M., Knowles, K. L., Stallard, T. S., K. Roberts & O’Donoghue, J. (2026). JWST discovers the vertical structure of Uranus' ionosphere. Geophysical Research Letters, 53(4), e2025GL119304. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL119304
Fig 1: Vertical profiles in different regions as observed by JWST on 2025-01-19. a) and b) H3+ temperature and number density, respectively, for auroral region 1 (A1, 0° - 112°W, dark grey), auroral region 2 (A2, 200° - 251°W, dark green), non auroral region 1 (NA1, 113° - 199°W, orange), non auroral region 2 (NA2, 252° - 360°W, brown), emission dip region (ED, 190° - 240°W, light grey). c) Limb data points projected on disk used for the different regional profiles, as described above, with L-shells contours from the Q3 model (Connerney et al, 1987).
Spring MIST @ NAM 2026
Spring MIST 2026 will be part of the National Astronomy Meeting 2026, taking place at the University of Birmingham on Monday 20 July to Friday 24 July 2026.
Website: https://uobevents-national-astronomy-meeting-2026.eventsair.site/
The call for abstracts is now open! Please submit your abstracts by 2 April 2026, 23:45 GMT.
The programme includes many MIST-related sessions:
- MIST Open Sessions
- The Science of Space Weather
- Space Weather Forecasting in the Big Data, Large Models Era
- X-ray Processes in the Solar System
- Energetic Particle Acceleration in the Sun and the Heliosphere [EPASunHelio]
- Magnetic Connectivity and Coronal Waves: From Chromosphere to Solar Wind [MagCon]
- Advances in machine learning and data analysis methods for solar, solar wind, and space weather applications with an emphasis on physical insight from large and complex datasets [MLSolar]
- Next Generation Observations and Theory of Solar Eruptive Events [NGEruptive]
- Instrumentation and Techniques in Space Situational Awareness [SpaceAware]
- Future Missions and Facilities [NewMissions]
- Protecting Dark & Quiet Skies: Practical mitigation for large satellite constellations [DarkSkies]