ARIES-led Study Finds Sun’s Meridional Flow Extends to Upper Chromosphere — Implications for Solar Dynamo

Key Developments Scientists from Aryabhatta Research Institute of Observational Sciences (ARIES) and partner institutes have shown that the Sun’s slow pole‑ward plasma movement, known as the meridional flow , continues up to the upper chromosphere . This discovery supports the long‑standing magnetic tree hypothesis and offers a new way to study the solar dynamo ." How the Study Was Conducted Analyzed 27 years (1999‑2025) of radio data from the Nobeyama Radioheliograph . Developed an image‑correlation technique that compares full‑disk images taken one day apart to detect minute shifts in brightness patterns. Mapped the large‑scale motion of bright radio features and linked them with long‑term magnetic field maps. Important Findings Pole‑ward plasma flow is present about 3,000 km above the visible surface. Flow speeds range from 5–15 m s⁻¹ , matching speeds measured in deeper layers. The flow varies with the solar cycle , and shows hemispheric asymmetry depending on magnetic activity. Bright radio features move pole‑ward in step with magnetic field transport, confirming a direct connection between high‑altitude structures and deep‑seated magnetic fields. UPSC Relevance The study links several GS‑4 topics: solar physics, space weather, and the impact of solar activity on satellite communication, navigation and power grids. Understanding the meridional flow and solar dynamo helps answer questions on how solar storms originate and affect national infrastructure – a frequent UPSC essay theme. Way Forward Extend the radio‑image correlation method to other wavelengths (e.g., EUV, X‑ray) for a multi‑layer view of solar dynamics. Integrate the findings into space‑weather forecasting models used by ISRO and the Ministry of Earth Sciences. Encourage collaborative research between Indian institutes (ARIES, PRL, IIT‑Delhi, IIST) and international agencies like NASA to monitor the Sun’s magnetic tree in real time. By proving that the Sun’s upper atmosphere retains memory of deep‑seated flows, the research provides a powerful tool for probing the solar interior and improving predictions of space‑weather events that can disrupt modern technology.