Abstract Details


Name: Kishor Dattatray Kumbhar
Affiliation: Department of Physics, University of Mumbai
Conference ID: TVS202510254
Title: Role of Kinetic instabilities in anisotropic heating and cooling of Corotating Interaction Regions at 1 Au
Authors and Co-Authors: Anil Raghav, Zubair Shaikh, Omkar Dhamane, Kalpesh Ghag, Ajay Kumar, Mohit Shah
Abstract Type: Contributory Presentation
Abstract: Corotating Interaction Regions (CIRs), formed by the interaction of fast and slow solar wind streams, and characterized by enhanced magnetic turbulence and elevated temperatures relative to the ambient solar wind. In this study, we investigate 465 Earth-directed CIR events observed by the Wind spacecraft from 1995 to 2009 to examine how microkinetic instabilities regulate proton heating and cooling near instability thresholds. The results reveal systematic signatures of anisotropic heating: the perpendicular proton temperature ($T_{p\perp}$) increases as plasma approaches the mirror mode (MM) threshold, while the parallel proton temperature ($T_{p\parallel}$) rises near the oblique firehose (OFH) threshold. Furthermore, plasmas unstable to proton cyclotron and parallel firehose instabilities exhibit substantially higher temperatures compared to stable plasma, in some cases by nearly a factor of three, indicating distinct and preferential heating pathways. Enhanced magnetic fluctuations are found close to the MM and OFH thresholds for $\beta_{p\parallel} > 1$, whereas plasmas with $\beta_{p\parallel} \leq 1$ show predominantly higher collisional age. Compressibility remains consistently elevated across all $\beta_{p\parallel}$ regimes, suggesting a robust role in shaping plasma dynamics. These findings collectively demonstrate that proton heating dominates over cooling in sustaining temperature anisotropy within CIR plasmas, while collisionality, compressibility, and magnetic fluctuations emerge as critical regulators of the overall plasma conditions.