- Why in news
- On 5 June 2026, the Ministry of Science & Technology reported an Indian Institute of Astrophysics study using 100+ years of Kodaikanal Solar Observatory data. It shows how the Sun's surface convection network responds to the 11-year solar cycle.
- What it is
- Kodaikanal Solar Observatory in Tamil Nadu holds India's oldest continuous series of solar data. It is run by the Indian Institute of Astrophysics, an autonomous institute under the Department of Science and Technology. Its archive of Ca II K spectroheliograms covers more than nine solar cycles and is used to study solar activity.
- Data source
- The study used about 34,000 Ca II K images from the Kodaikanal archive, starting from 1907.
- Who ran it
- Scientists from the Indian Institute of Astrophysics, an autonomous institute of DST, led by Prof KP Raju, did the study.
- Network cell size
- Network cells last about 24 hours on average and are about 30,000 km across.
- Time lag
- Lane-width correlations peak at solar maximum, while intensity correlations peak 1.25–1.5 years after it.
- Cycle coverage
- The archive covers more than nine solar cycles. The NLST is expected to add high-resolution studies of supergranular dynamics.
Don’t confuse with Granulation vs supergranulation: Granulations are small-scale convective cells; supergranulations are large-scale cells forming the network structure on the solar surface.
Don’t confuse with Solar minimum vs maximum: Minimum is the low point of the roughly 11-year activity cycle (e.g. 1913 in the figure); maximum is the peak (e.g. 1917).
Science and technology: 57 Prelims questions since 2013; most test the concept behind the news, not the news itself. In Mains, 12 news-triggered questions.
Why it matters
- Better understanding of supergranulation can improve solar cycle prediction.
- Helps estimate variations in solar irradiance, especially UV, which affects space weather and satellites.
Problems
- The origin and size determination of supergranulations remain unresolved.
- No single latitude tracks the solar cycle for all quantities, which complicates prediction.
Way forward
- Combine century-long archives with high-resolution facilities such as the NLST.
- Pursue further research on mechanisms behind the observed lags.
Put in your answer
Kodaikanal archive: India's oldest continuous solar data series, covering more than nine solar cycles, shows the value of long-term scientific records.
UPSC’s own questions that come close to this issue, from our Prelims and Mains banks.
No practice question for this one; the card may still help an answer. Why: Study result on supergranulation; observatory is a lasting topic. Sci-tech Prelims asks mostly concepts (36 of 57), so no question here.
Worth revising until Prelims 2028: most news questions come within two years of the event.