Kodaikanal Solar Observatory Data Maps Solar Magnetic Patterns Impacting Space Weather
Astronomers from the Indian Institute of Astrophysics (IIA) have developed a new method to trace how the Sun’s magnetic activity varies with latitude, shedding light on the mechanisms driving solar cycles and their effects on Earth’s space environment. The research, based on long-term observations from the historic Kodaikanal Solar Observatory, offers valuable insights into how solar magnetic fields influence satellite communication and climate systems.
Tracking the Sun’s Magnetic Rhythm
The Sun, far from being a static sphere of plasma, is a dynamic, magnetically active star that follows an approximately 11-year cycle of activity. These fluctuations are crucial to understanding space weather, which can disrupt satellite operations, navigation systems and even terrestrial power grids.
The IIA team analysed 11 years of data (2015–2025) captured at the Kodaikanal Solar Observatory using the calcium K (Ca-K) spectral line, which appears at 393.4 nm in the violet region of the spectrum. This spectral line, originating in the Sun’s chromosphere—the layer above its visible surface—acts as a powerful diagnostic tool for tracing magnetic activity. Continuous daily solar observations from the observatory, which recently marked its 125th anniversary, have provided an unparalleled record of the Sun’s changing behaviour.
Innovative Method Reveals Latitude-Based Activity
Instead of examining individual sunspots, the researchers applied a technique developed by IIA professor Jagdev Singh, which involves analysing sunlight from entire latitude bands across the Sun. “We sliced the Sun into horizontal strips from pole to pole and studied the combined light from each band,” explained K. P. Raju of IIA. “This helps reveal large-scale magnetic patterns that isolated features might miss.”
By measuring the widths and intensity ratios of multiple components within the Ca-K spectral line, the team tracked changes in solar magnetic activity across latitude bands from the peak of solar cycle 24 through the rise of the ongoing cycle 25.
Their results showed that most solar magnetic activity is concentrated between 40° north and south, with particularly strong signals near 15°–20° in both hemispheres—the same regions where sunspot activity typically peaks. These findings were confirmed through comparisons with NASA’s Solar Dynamics Observatory (SDO) data, using filling factor analysis to correlate spectral signals with actual magnetic coverage on the Sun’s surface.
Hemispheric Asymmetries and Solar Dynamo Insights
The study also uncovered clear north–south asymmetries in solar behaviour. The southern hemisphere displayed steeper increases in magnetic activity at higher latitudes and stronger correlations with magnetic indicators. By calculating how the spectral line’s shape changed with varying magnetic intensity, the researchers produced “spectral response profiles” that revealed systematic latitude-dependent differences between the hemispheres.
“These asymmetries provide important clues about the workings of the solar dynamo—the process that generates the Sun’s magnetic field,” said K. Nagarju, an IIA faculty member and co-author. Apoorva Srinivasa, now a PhD researcher at Amrita Vishwa Vidyapeetham, added, “Our results confirm that solar activity follows predictable latitude-based patterns that evolve over the solar cycle, reflecting underlying changes in temperature and magnetic strength across the chromosphere.”
The study, published in the Monthly Notices of the Royal Astronomical Society, was co-authored by researchers from IIA, IIT BHU and Amrita Vishwa Vidyapeetham. The findings not only enhance understanding of the Sun’s magnetic evolution but may also improve predictive models of space weather—vital for protecting communication satellites and power infrastructure on Earth.
with inputs from Reuters