Astronomers have unraveled the intricate reasons behind a series of powerful solar eruptions that resulted in lighting up the skies over Ladakh during May 2024 in a manner similar to the northern lights experienced in the Arctic regions. The intensity of this rare phenomenon, called Coronal Mass Ejections (CMEs) was unlike any seen in the past 20 years.
CMEs are massive ejections of magnetised plasma from the Sun’s corona. When such solar blasts are directed toward the Earth, they can cause geomagnetic storms capable of disrupting satellite operations, communication systems and power grids.
The geomagnetic storm that started on May 10, 2024, was linked to a rare sequence of six different CMEs erupting in succession, associated with both solar flares and filament eruptions from an interacting complex active region on the Sun, according to a study carried out by the faculty at the Indian Institute of Astrophysics (IIA) using data from the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA).
A team of solar astrophysicists led by Dr Wageesh Mishra, built a model to investigate the manner in which the rare chain of six interacting solar blasts reported from IIA’s Indian Astronomical Observatory in Hanle, Ladakh, interacted with each other and evolved thermally during its travel from the Sun to Earth.
The team traced not just the paths, but the temperatures and magnetic states of these blasts as they expanded across the solar system. Surprisingly, they found that these solar clouds do not just carry heat, but they also change their thermal behaviour mid-way. Initially, the CMEs release heat but then enter a state where they actually absorb and hold onto it.
At the Earth’s doorstep, using data from the Wind spacecraft, scientists found something even stranger. The final storm cloud had two intertwined magnetic structures called ‘double flux ropes’. These acted like tangled magnetic braids with compressed fields and odd patterns of heating and cooling between electrons and ions.
“Using wide-field coronagraphic data and an analytical framework known as the Flux Rope Internal State (FRIS) model, we tracked the thermodynamic evolution of six CMEs and their mutual interactions in interplanetary space,” Soumyaranjan Khuntia, the lead author of the study said in a statement issued on Wednesday.
The study revealed that most CMEs initially released heat, but later transitioned into a state that gets heated instead, particularly to a near-constant temperature state as they expanded further from the Sun.
“This study is the first-of-its-kind, both in India and internationally, to capture the continuous thermodynamic evolution of multiple interacting CMEs across such a vast distance in the heliosphere,” Dr Wageesh Mishra, a faculty member at IIA said. The findings have been published in the Astronomy and Astrophysics, a peer reviewed journal brought out every month on behalf of the European Southern Observatory.
Until now, gaining a complete understanding of how CMEs evolve thermodynamically as they travel from the Sun to Earth has remained challenging, primarily due to limited observations near the Sun as well as in near-Earth space.
“This work marks an important step toward understanding the thermal signatures associated with the ability of CMEs and their evolving substructures to disturb Earth’s space environment. Our aim is to explore whether thermal properties can be used as precursors to forecast intense geomagnetic disturbances,” said Anjali Agarwal, co-author of the work.
