The Impressive TimesA team of astronomers, led by researchers from the Indian Institute of Astrophysics (IIA), has discovered miniature plasma loops in the lower layers of the Sun’s atmosphere, offering new insights into one of solar physics’ most enduring mysteries—how the Sun stores and unleashes magnetic energy.
These tiny loops, found in the solar corona—the Sun’s outer atmosphere—are just 3,000 to 4,000 kilometers long but less than 100 kilometers wide. They are short-lived, existing for only a few minutes, making them extremely difficult to detect using traditional solar observation methods.
Despite their size, these coronal micro-loops may hold critical clues to understanding high-energy phenomena such as solar flares and plasma jets. The discovery was made possible by combining data from multiple cutting-edge observatories, including NASA’s Solar Dynamics Observatory (SDO), the Interface Region Imaging Spectrograph (IRIS), and the Goode Solar Telescope (GST) at Big Bear Solar Observatory in the USA.
“These tiny loops live fast and die young, but they punch above their weight in terms of scientific value,” said Annu Bura, Ph.D. student at IIA and lead author of the study published in The Astrophysical Journal. “They offer a fresh perspective on how magnetic energy is built up and released in the solar atmosphere.”
The research team used multi-wavelength observations—visible, ultraviolet, and extreme ultraviolet—to track these elusive features across different layers of the Sun’s atmosphere: the chromosphere, the transition region, and the corona. Using the H-alpha spectral line, a key diagnostic for the chromosphere, the loops were observed as bright, delicate arcs similar to their larger counterparts in the corona.
The team also detected significant spectral broadening using IRIS data, suggesting highly non-thermal activity due to magnetic fields—a sign of magnetic reconnection, where tangled magnetic lines break and reconnect, releasing intense energy.
“We also observed upward plasma jets erupting from the tops of these loops,” said Dr. Tanmoy Samanta, co-author and IIA faculty member. “These jets likely originate from the same reconnection events, mirroring the behavior of larger solar jets.”
To understand the thermal properties of these loops, the team applied a method called Differential Emission Measure (DEM) analysis. The results showed plasma temperatures reaching several million degrees—hot enough to be visible in the extreme ultraviolet spectrum captured by SDO.
“This is particularly surprising because these loops reside in the chromosphere, a region with much higher plasma density than the corona,” said Dr. Jayant Joshi, IIA faculty and study co-author. “Heating such dense plasma to extreme temperatures remains a challenge for current solar models. Future high-resolution spectroscopy may provide the answers.”
Looking ahead, India’s upcoming National Large Solar Telescope (NLST)—a 2-meter aperture facility planned near Pangong Lake in Ladakh—is expected to enhance the country’s capabilities in solar observation, particularly in high-resolution chromospheric imaging and magnetic field mapping.
This international collaboration also involved scientists from NASA, the Max Planck Institute for Solar System Research (Germany), and Big Bear Solar Observatory (USA), highlighting the global effort to decode the Sun’s most complex magnetic behaviors.
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