Earth and Space Weather: An Interdisciplinary Research

With Solar Cycle 25 reaching its maximum, the vulnerability of LEO infrastructure to space weather has become a critical operational challenge. The extreme geomagnetic storm in May 2024, known as the `Mother`s Day Storm`, served as a stark stress test: while producing widespread auroras, it triggered unexpected atmospheric drag, causing satellites to experience significantly greater orbital decay than predicted. The ESPIRE project (Earth and Space Weather: Interdisciplinary Research), led by the Institute of Geodesy at Graz University of Technology, seeks to advance prediction capabilities by synthesizing expertise from satellite geodesy, heliospheric physics, and planetary aeronomy. Despite significant improvements in empirical thermosphere models over the last few decadesdriven by the integration of LEO satellite observationsdensity estimation remains a major challenge. This is partly because current models rely on solar proxies with limited temporal resolution and treat solar events as isolated incidents, struggling to account for complex ejecta. ESPIRE will investigate the phenomenon of `preconditioning`, whereby a sequence of Coronal Mass Ejections (CMEs) alters the state of the interplanetary medium, as observed during the 2024 storm where the cumulative impact caused an altitude loss of nearly 70 meters at 490 km. When CMEs interact to form `complex ejecta`, they compress magnetic fields and accelerate plasma, leading to cumulative atmospheric heating that standard proxies like the F10.7 radio flux cannot fully capture. ESPIRE proposes integrating physical processes into density modelling alongside statistical correlations. Utilizing the Drag-Based Model (DBM) and in-situ data (e.g., ACE, GOES), the project aims to reconstruct the interaction of multiple CMEs to isolate contributions from simultaneous flares. A major uncertainty addressed is the aerodynamic drag coefficient, which depends on how gas molecules exchange energy with satellite surfaces; this will be estimated using GRACE-FO accelerometer data and validated against Earth gravity field recovery data. Finally, to address the underestimation of heating by energetic particles, ESPIRE adapts the 1-D THP-MoCaCo model to simulate the specific impact of CME-driven electron precipitation and the production of supra-thermal oxygen and nitrogen atoms. This interdisciplinary effort unites Graz University of Technology, the University of Graz, and the Austrian Academy of Sciences, strengthening Graz`s position as a center for space research

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