Summary
In the JOIN project, the team will develop new tools for estimating the amount of Joule Heating in the Northern auroral regions, and carry out a detailed investigation of its consequences on the neutral atmosphere at satellite altitudes. The high-latitude auroral ionosphere is connected by magnetic field lines to a large part of the magnetospheric volume, making it a “focus area” of near-Earth plasma dynamics. Consequently, space weather disturbances are also most strongly manifested at high latitudes.
During geomagnetic storms large amounts of energy originating from the solar wind is deposited in the auroral ionosphere as Joule heating at 100-150 km altitudes. This causes the tenuous upper atmosphere to heat up and expand, which results in increased atmospheric drag experienced by satellites at low-Earth obits (LEO). Understanding the detailed spatial and temporal dynamics of the Joule heating is a key task in developing successful space weather forecasts, needed to protect our satellite fleets from adverse effects.
An important aspect of the JOIN project is to distinguish between different types of solar wind structures that drive geomagnetic storms, namely solar wind high speed streams (HSS) or interplanetary coronal mass ejections (ICME), and to investigate possible differences in the atmospheric responses to these drivers. The main objectives or the Science Cases are to:
- Determine the statistical distribution and variability of the high-latitude Joule heating during geomagnetic storms driven by HSSs or ICMEs.
- Correlate the storm-time Joule heating with large-scale atmospheric density variations observed by the Swarm and GRACE satellites.
- Study and characterize the atmospheric scale height by directly comparing simultaneous and co-planar density measurements from two different altitudes during different solar and geomagnetic conditions.
- Perform event studies of meso-scale density variations at auroral regions by utilizing conjunctions between the Swarm satellites and ground-based Incoherent Scatter (IS) radars (ISR).
Together, these Science Cases will reach multiple science objectives mentioned under Theme 3 “Ionosphere – Upper Atmosphere/Thermosphere coupling” of the ESA’s 4D Ionosphere initiative.
Submitted manuscripts and published articles
Cai L., A.T. Aikio, G.P. Geethakumari, H. Vanhamäki, I.I. Virtanen, S. Oyama, Y. Zhang, J. Zhang, and M.R. Hairston: “Ionosphere-Thermosphere Coupling in the Northern Polar Region during the May 2024 Geomagnetic Superstorm”. Manuscript submitted to Journal of Geophysical Research, 2025.
Presentations at conferences
- Iorfida E., L. Küchelbacher, S. Wüst , W. Miloch, H. Vanhamäki, A. Dimmock, C. Finlay, I. Daras, R. Sabia, A. Strømme, L. Trenchi, M.G.G.T. Taylor, D. Prieto: “ESA Swarm 4D Ionosphere: outline of the five contributing studies“. Swarm 10 Years Anniversary & Science Conference, poster presentation, Copenhagen, 8-12 April 2024.
- Iorfida E., C. Schmidt, W. Miloch, E. Doornbos, A. Aikio, S. Buchert, C. Finlay, A. Strømme, and D.F. Prieto: “4D Ionosphere – where we stand and where we are going”. Living Planet Symposium, panel discussion, Vienna, 23-27 June 2025.
- Pedersen M., H. Vanhamäki, A. Aikio, L. Cai, and M. Myllymaa: “Joule heating effects on ionosphere-thermosphere coupling and neutral density (JOIN) project: preliminary results”. European Space Weather Week, poster presentation, Coimbra, 4–8 November 2024.
- Pedersen, M., H. Vanhamäki, A. Aikio, L. Cai, M. Myllymaa, C. Waters, and J. Gjerloev: “Joule heating and neutral density enhancements during geomagnetic storms driven by solar wind high-speed streams and coronal mass ejections“, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, https://doi.org/10.5194/egusphere-egu25-16944, 2025.
- Vanhamäki, H., L. Cai (presenting author), A. Aikio, M. Pedersen, and M. Myllymaa: “Variations of upper thermospheric scale height based on neutral mass density measurements from coplanar low-Earth-orbit satellites“, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15392, https://doi.org/10.5194/egusphere-egu25-15392, 2025.
- Vanhamäki H., A. Aikio, L. Cai, M. Pedersen and M. Myllymaa: “Ionospheric Joule heating and neutral density variations at low Earth orbits during geomagnetic storms”. Living Planet Symposium, Vienna, 23-27 June 2025.
