Solar Coronal Mass Ejections and their associated sheaths are considered the primary drivers of Earth's space weather disturbances, ranging from disruptions in communication to astronaut safety hazards. Therefore, a good understanding of near-Earth interplanetary CMEs (ICMEs) and their associated sheaths is crucial for the better prediction of space weather impacts. The thermodynamics of near-Earth ICMEs and sheaths play a key role in characterising them. Their thermodynamics are often described using polytropic processes, and the estimation of the polytropic index provides a way to quantify the compression/expansion arising from changes in temperature. In this talk, I will discuss the proton polytropic index within near-Earth ICMEs, sheaths, and the ambient solar wind for a large set of well-observed events observed by the Wind spacecraft. The discussion will focus on how the polytropic index varies in these regions and how it is connected to small-scale density fluctuations. I will also outline our attempts to quantify the proton heat flux from the solar corona to the ICMEs, based on sub-adiabatic assumptions, and determine whether it agrees with the required heating budget.
Dr. Debesh Bhattacharjee is currently a Postdoctoral Fellow at the Udaipur Solar Observatory (USO), PRL, Udaipur. Prior to his current appointment at USO, he was a UKRI-STFC Postdoctoral Researcher at the School of Physics and Astronomy, University of Glasgow, from August 2023 to June 2025, working with Prof. Eduard Kontar. He earned his MS from IISER Pune in August 2017 and his PhD in 2023 under the supervision of Prof. Prasad Subramanian. As a DAAD Visiting Researcher (2020), he worked with Prof. Volker Bothmer at the University of Goettingen, Germany. He was also involved in the Indo-US Science and Technology Forum project (2022–2024) on understanding CME propagation and internal structure in interplanetary space to predict Bz. He is actively engaged with scientific communities and is a member of the Royal Astronomical Society (RAS), a junior member of the International Astronomical Union (IAU), and a lifetime member of the Astronomical Society of India (ASI).
Wageesh Mishra