New model reveals heat budget & thermal evolution of CMEs

Bengaluru: A new model developed by researchers led by astronomers from the Indian Institute of Astrophysics (IIA) has uncovered important details about the heat budget and thermal evolution of coronal mass ejections (CMEs) as they travel from the Sun towards Earth.CMEs are huge eruptions of plasma and magnetic fields from the outer atmosphere of the Sun. If Earth-directed, they can adversely impact our planet’s space weather and infrastructure in space. However, how hot a CME is when it leaves the Sun and how it cools during its journey to Earth has been unclear. A team led by Wageesh Mishra from IIA in Bengaluru has created a model that tracks the continuous thermodynamic changes in CMEs — information critical for understanding their potential effects on Earth. The model takes CME kinematic data as inputs. “Our indigenously developed model provided a comprehensive profile of how CME thermodynamic parameters evolve over time,” Soumyaranjan Khuntia, a PhD student at IIA and the lead author of the new study, said. The researchers applied the model to two specific past CMEs that had multi-spacecraft and telescope observations. They discovered that fast and slow CMEs heat and cool differently while travelling through interplanetary space. The fast CME released heat early on when decelerating rapidly but absorbed heat later as it expanded away from the Sun. By contrast, the slow CME showed heat absorption during its gradual acceleration phase but steady temperature afterwards.“The contrasting thermal evolutions confirm CMEs undergo heating/cooling processes indicating transactions of thermal energy,” said Mishra. The findings also underscore the distinct forces driving CME expansion over time. The study demonstrates the value of probing CME internal thermodynamics for predicting space weather impacts on Earth. “We hope to combine data from India's recently launched Aditya-L1 solar mission with our model to advance Sun-Earth connection research,” Mishra added.This research has been accepted for publication in The Astrophysical Journal (ApJ) and is co-authored by IIA’s Wageesh Mishra, Sudheer K Mishra from Astronomical Observatory, Kyoto University, Japan, Yuming Wang & Shaoyu Lyu from CAS Key Laboratory of Geospace Environment, University of Science and Technology of China, and Jie Zhang from Department of Physics and Astronomy, George Mason University, USA.