Kodaikanal Observatory’s 100-Year Solar Data May Help Predict Solar Storms

Researchers at the Aryabhatta Research Institute of Observational Sciences (ARIES) have developed a new method to reconstruct the Sun’s polar magnetic behaviour over the last century by analysing historic solar images from the Kodaikanal Solar Observatory (KoSO), the government said on Wednesday.

The team, led by Dibya Kirti Mishra of ARIES, collaborated with scientists from the Indian Institute of Space Science and Technology, the US-based Southwest Research Institute, Germany’s Max Planck Institute for Solar System Research, and Italy’s INAF Osservatorio Astronomico di Roma to estimate the Sun’s polar magnetic field spanning more than 100 years.

According to the Ministry of Science and Technology, understanding the Sun’s magnetic activity is crucial because it helps scientists predict solar storms—powerful eruptions that can damage satellites, disrupt GPS signals, and even cause large-scale power outages on Earth.

With over a century of solar observations now digitised, KoSO’s vast archive serves as a major “big data” source for modern AI and machine learning applications. By integrating these historic records with recent observations from Italy’s Rome-PSPT, researchers applied advanced feature-detection algorithms to locate tiny bright elements near the Sun’s poles, known as the polar network. These features were then used to estimate the Sun’s polar magnetic field.

The study found that the polar network is a highly reliable "proxy"—an indicator of polar field strength—and used this reconstruction to assess the strength of the ongoing Solar Cycle 25.

KoSO has been observing the Sun in the Ca II K wavelength since 1904, a spectrum that reveals chromospheric activity and highlights bright magnetic structures such as plages and networks. These century-old observations have preserved vital clues about the Sun’s magnetic history.

Located in Bengaluru, KoSO is an autonomous institution under the Department of Science & Technology (DST), Government of India.

The complete dataset, including the reconstructed polar field and the Polar Network Index (PNI) series, is publicly accessible on GitHub and Zenodo.

With inputs from IANS