Indian Study Improves Understanding of Solar Storm Threats

Scientists from the Indian Institute of Astrophysics (IIA), Bengaluru, studied Interplanetary Coronal Mass Ejections (ICMEs), which are massive clouds of magnetised plasma released from the Sun's outer atmosphere.

A team of Indian astrophysicists has made a significant breakthrough in understanding how powerful solar eruptions behave during their journey from the Sun to Earth, offering fresh insights that could improve space weather forecasting and help protect satellites, communication networks, aviation, and power infrastructure. Scientists from the Indian Institute of Astrophysics (IIA), Bengaluru, studied Interplanetary Coronal Mass Ejections (ICMEs), which are massive clouds of magnetised plasma released from the Sun's outer atmosphere. When these eruptions travel towards Earth and interact with the planet's magnetic field, they can trigger geomagnetic storms that disrupt GPS services, radio communication, satellite operations, aviation routes, and electricity grids, while also producing spectacular auroras in the upper atmosphere.

Nearly three decades of data reveal surprising thermal patterns

The research team analysed 29 years of publicly available observations collected between 1995 and 2024, covering Solar Cycles 23, 24, and the rising phase of Cycle 25. Using data from NASA's OMNI database, which combines measurements from spacecraft positioned near the Earth-Sun L1 point, the researchers examined how the temperature and pressure of ICMEs change as they travel through space.

The study focused on calculating the polytropic index, a parameter that helps describe how the plasma inside these solar eruptions evolves over time. Earlier research mainly concentrated on the speed, magnetic structure, or individual events, leaving the thermal behaviour of ICMEs largely unexplored. This long-term statistical analysis fills that gap by examining the thermal state of each event individually.

The findings challenge the common assumption that these solar eruptions simply cool as they expand. Instead, the researchers discovered that nearly 45 percent of magnetic ejecta actually show signs of heating by the time they reach Earth's orbit, particularly during periods of high solar activity. They also found that Solar Cycle 23 experienced more heating-like behaviour, while Solar Cycle 24 was dominated by cooling, suggesting that the Sun's overall magnetic environment plays a major role in shaping the thermal evolution of these eruptions.

Better forecasting could strengthen space weather preparedness

The study, published in the Monthly Notices of the Royal Astronomical Society (MNRAS), also found a strong connection between the thermal state of ICMEs and the intensity of geomagnetic storms experienced on Earth. The most severe storms were linked to solar eruptions that remained in a heating state, accompanied by stronger magnetic fields, compressed plasma regions, and faster expansion speeds.

Lead author Soumyaranjan Khuntia said understanding these thermal signatures could provide an early indicator of how dangerous an approaching solar storm may become. Associate Professor Wageesh Mishra added that combining thermal measurements with magnetic and plasma observations creates a more comprehensive framework for predicting space weather impacts.

The researchers plan to extend this work by using observations from India's Aditya-L1 solar mission, allowing scientists to monitor the thermal evolution of solar eruptions much closer to the Sun and further improve forecasting models for future space weather events.