A series of powerful Coronal Mass Ejections (CMEs) in May 2024 led to rare northern lights visible in Ladakh, India. This solar storm was described as unlike any seen in the past 20 years.

About Coronal Mass Ejections (CMEs)

• Refers: Large expulsions of plasma and magnetic fields from the Sun’s corona into space. 
  • CMEs often look like huge, twisted ropes, which scientists call “flux ropes.”
• Frequency of Occurrence: It varies with the year’s solar cycle (during solar minimum & Solar maximum)
• Impact: When directed towards Earth, CMEs can cause geomagnetic storms, disrupting satellites, communication systems, and power grids.
• Magnetic Field Merging: CMEs merge magnetic fields between the interplanetary magnetic field (IMF) and Earth’s geomagnetic field, intensifying energy transfer into the magnetosphere.
  • Due to this enhanced energy coupling, CMEs are major drivers of geomagnetic storms and substorms.
  • These substorms lead to spectacular auroras (northern and southern lights) visible at high latitudes.
• Broad Plasma Temperature Range: CME plasma spans temperatures from cold chromospheric material (~10⁴ K) to hot coronal plasma (~10⁷ K).
• Complex Energy Exchange: During propagation, CMEs undergo electrical, kinetic, potential, and thermal energy exchanges, causing internal plasma heating or cooling.
• Relevance to Earth Systems: Studying CMEs is crucial to predict and mitigate their impact on Earth’s communication, navigation, and power infrastructure.

Key Findings on CME Thermal Behavior

• Mid-Journey Thermal Shift: CMEs initially release heat, but later absorb and retain it, stabilizing at near-constant temperatures mid-journey.
• Double Flux Ropes Detected: Wind spacecraft data revealed intertwined magnetic structures at Earth’s doorstep, with compressed fields and unusual electron-ion thermal patterns.
• CME-CME Interactions: Interacting CMEs undergo thermal restructuring.
  • Electrons: Heat-releasing state
  • Ions: Mixed states, heating dominant
• Pioneering Insight: First-ever continuous tracking of multi-CME thermodynamics across heliosphere — a landmark Indian and global contribution.

Implications for Space Weather Forecasting

• Enhanced Models: A leap forward in space weather prediction accuracy, as published in Astronomy and Astrophysics Journal.
• Magnetosphere Impact Forecasting: Aids prediction of complex geomagnetic disturbances caused by interacting CMEs.
• Future Sun-to-Earth Tracking: Upcoming data from Aditya-L1 (VELC & ASPEX) to refine models and explore if thermal indicators act as precursors to major space weather events.
  • Aditya-L1 is India’s first dedicated solar mission, carrying seven scientific instruments, including the Visible Emission Line Coronagraph (VELC) and the Aditya Solar Wind Particle Experiment (ASPEX).

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