CHENNAI: Daily solar observations gathered for years at the century-old Kodaikanal Solar Observatory (KSO) have led to an understanding of how the Sun’s magnetic activity varies across its latitudes – a discovery that could deepen insights into the solar dynamo, impact space-weather forecasting, and even help climate models.
The study, led by researchers from the Indian Institute of Astrophysics (IIA), an autonomous body under the Department of Science and Technology (DST), analysed 11 years (2015–2025) of spectroscopic data captured in the calcium-K line of sunlight – a spectral signature that forms high in the Sun’s chromosphere and serves as a sensitive marker of magnetic activity.
“All the studies on the Sun are ultimately essential to understand the space weather, which has direct consequences on the Earth. So, the more we understand, the better prepared we can be for possible disruptions to catastrophes,” Apoorva Srinivasa, one of the authors of the study.
The KSO, which recently celebrated 125 years of continuous observation, maintains one of the world’s longest solar datasets. The research team used this archive to track how the Sun’s magnetic intensity changes across latitudes – revealing consistent zones of heightened activity that correspond with the Sun’s well-known 11-year cycle of sunspot peaks.
“The Sun is not a static ball of fire, but a magnetically active star that follows large-scale cycles of activity,” said KP Raju, lead author of the study. “By slicing the Sun into latitude bands and analysing integrated light from each, we can reveal patterns invisible when studying isolated features like sunspots,” added the former professor at IIA.
The team found that most magnetic activity clusters between 40 degrees north and south latitude, with pronounced peaks around 15 degrees to 20 degrees, matching zones where sunspots are most frequent. “These spectral variations directly mirror how the Sun’s magnetic field evolves,” said co-author K Nagarju, associate professor at IIA, whose focus area of research is solar magnetism. “We verified this correlation using data from NASA.”
They also observed hemispheric asymmetries – with the southern hemisphere generally showing stronger or faster variations in activity – providing new hints about how the internal magnetic field reorganises itself over each solar cycle. The findings were published in the journal, ‘Monthly Notices of the Royal Astronomical Society’ and represent a step toward refining solar dynamo models, which explain how magnetic energy is generated and cycles through the Sun’s surface.
Kodaikanal data opens new research paths – including the possible use of machine learning in solar studies.