Understanding the Complex Dynamics of Solar Eruptions
Astronomers have recently uncovered a detailed account of a series of powerful solar eruptions known as Coronal Mass Ejections (CMEs), which led to rare northern lights visible across Ladakh’s night skies in May 2024. This event marked a significant solar storm, one of the most intense in the past two decades. The findings were shared through a press release highlighting the importance of these observations.
CMEs are massive ejections of magnetized plasma from the Sun’s outer atmosphere, or corona. When directed towards Earth, they can trigger geomagnetic storms that disrupt satellite operations, communication systems, and power grids. The geomagnetic storm that began on May 10, 2024, was linked to a rare sequence of six CMEs erupting in succession. These eruptions were associated with both solar flares and filament eruptions from an interacting complex active region on the Sun.
Until now, understanding how CMEs evolve thermodynamically as they travel from the Sun to Earth has been challenging due to limited observations near the Sun and in near-Earth space. To address this gap, a team of solar astrophysicists led by Dr. Wageesh Mishra from the Indian Institute of Astrophysics (IIA) used data from NASA and ESA space missions.
The researchers developed a model to study the interactions and thermal evolution of the rare chain of six solar blasts observed at IIA’s Indian Astronomical Observatory in Hanle, Ladakh. Their work aimed to trace not only the paths of these blasts but also their temperatures and magnetic states as they expanded across the solar system.
Surprisingly, the team discovered that these solar clouds do not merely carry heat—they change their thermal behavior mid-journey. Initially, the CMEs release heat, but then they enter a state where they absorb and retain it. At Earth’s doorstep, using data from the Wind spacecraft, scientists found something even more intriguing: the final storm cloud had two intertwined magnetic structures called “double flux ropes.” These acted like tangled magnetic braids, with compressed fields and unusual patterns of heating and cooling between electrons and ions.
Key Findings and Implications
Using wide-field coronagraphic data and an analytical framework known as the Flux Rope Internal State (FRIS) model, the team tracked the thermodynamic evolution of six CMEs and their mutual interactions in interplanetary space. The study revealed that most CMEs initially released heat but later transitioned into a state that gets heated instead, particularly reaching a near-constant temperature as they expanded further from the Sun.
“Our analysis demonstrates that CME-CME interactions lead to significant thermal restructuring within. By the time they reach Earth, the electrons in the complex ejecta were found to be in the heat-releasing state, while ions displayed a mix of heating and cooling behavior, with the heating state being the dominant mode overall,” said Soumyaranjan Khuntia, the lead author and a doctoral scholar at IIA.
This research marks a first in India and internationally, capturing the continuous thermodynamic evolution of multiple interacting CMEs across vast distances in the heliosphere. The findings, published in the Astronomy and Astrophysics Journal, represent a significant step forward in improving space weather forecasting models, especially in predicting the impact of complex CME events on Earth’s magnetosphere.
Dr. Mishra highlighted the potential for future research, including incorporating observations from India’s Aditya-L1 space mission, such as those from the Visible Emission Line Coronagraph (VELC), as well as observations from spacecraft closer to the Sun and near-Earth observations from the Aditya Solar wind Particle Experiment (ASPEX). These instruments will enable a comprehensive study of CMEs from the Sun to Earth.