Kinematics and Thermodynamics of Coronal Mass Ejections

Abstract

Coronal mass ejections (CMEs) are major drivers of space weather, yet their thermodynamic evolution remains insufficiently constrained. This thesis develops a comprehensive framework linking CME kinematics, thermodynamics, internal force balance, and geoeffectiveness through analytical modelling and multi-viewpoint observations. The developed FRIS model uses observed kinematics to infer otherwise inaccessible internal plasma properties, including the polytropic index. A systematic investigation of fast CMEs reveals an initial heat-release phase followed by a transition towards near-isothermal evolution, typically around 3-9 solar radii. The evolving contributions of thermal-pressure and centrifugal forces, opposed by the Lorentz force, establish a connection between expansion and thermal evolution. The findings demonstrate the limitations of assuming a fixed polytropic index in magnetohydrodynamic models of CME propagation. At 1 au, in situ observations reveal persistent non-adiabatic evolution, accompanied by turbulence and localised intermittency. The interacting CMEs associated with the May 2024 great storm show restructured magnetic and thermal configurations, producing double-flux-rope-like signatures and species-dependent heating, with electron thermodynamics as a better indicator of recent interactions. Statistical analysis of nearly 600 ME demonstrates that 45% exhibit net heating with a solar cycle dependence. Notably, High-impact ejecta preferentially exhibit stronger heating signatures, establishing thermal state as a complementary diagnostic of geoeffectiveness. Overall, this thesis establishes CMEs as intrinsically non-adiabatic systems whose thermodynamic evolution is coupled to expansion, internal force balance, solar-cycle variability, and CME-CME interactions, with important implications for understanding geoeffectiveness and improving space-weather assessment.