Thermal Signatures of Three Decades of Solar Storms at Earth Reveal New Clues for Space Weather Forecasting

📌 Summary:

• Astrophysicists at the Indian Institute of Astrophysics (IIA), Bengaluru (an autonomous DST institute) performed the first long-term statistical study of the thermal behaviour of Interplanetary Coronal Mass Ejections (ICMEs) at 1 AU (near Earth)
• Used 29 years of data (1995-2024) spanning solar cycles 23, 24 and the rising phase of 25, drawing on the NASA OMNI database of L1-point solar-wind measurements and a polytropic-index framework
• Key finding: contrary to the assumption that CMEs cool as they expand, nearly 45% of magnetic ejecta show heating signatures at 1 AU, especially near solar maximum - implying active in-transit heating
• Observed a systematic shift from heating-dominated states in Cycle 23 to cooling-dominated states in Cycle 24, modulated by the global solar magnetic environment - a novel insight for heliophysics
• ICMEs trigger geomagnetic storms that disrupt satellites, GPS/radio communications, aviation routes and power grids; understanding thermal state improves space-weather forecasting. Study published in MNRAS

🎯 UPSC Relevance: GS3 (Science & Technology - space science, space-weather preparedness, indigenous R&D).

📝 Prelims Facts:

• ICME = Interplanetary Coronal Mass Ejection; study conducted at 1 AU using L1-point (1.5 million km sunward) data
• Conducted by Indian Institute of Astrophysics (IIA), Bengaluru, under DST; published in Monthly Notices of the Royal Astronomical Society (MNRAS)
• Solar activity follows an ~11-year cycle; current Cycle 25 peaked in 2025
• ~45% of magnetic ejecta show heating signatures at 1 AU

🔑 Key Term: Geomagnetic storm - a disturbance of Earth's magnetosphere caused by solar eruptions (ICMEs) that can disrupt satellites, navigation, communications and power grids.