Hidden Flow in the Sun’s Upper Atmosphere

Why in News?

Recently, Scientists revealed a hidden flow in the Sun's upper atmosphere, providing new insights into space weather that affects satellites, communication, navigation and power grids on Earth.         

• Study led by –
  • Aryabhatta Research Institute of Observational Sciences (ARIES), autonomous institute under the Department of Science and Technology (DST),
  • Physical Research Laboratory (PRL)
  • Indian Institute of Technology Delhi (IIT Delhi)
  • Indian Institute of Space Science and Technology (IIST)
  • NASA’s Goddard Space Flight Centre.

Key findings

• Meridional flow – The Sun has a slow flow of hot gas or plasma moving from equator to poles like a conveyor belt, this movement is called meridional flow.
• It plays and important role in controlling the 11‑year solar cycle which influences the appearance of sunspots.
• Upper Chromosphere – The slow poleward movement of plasma flow exists 3,000 km above the Sun’s visible surface i.e. the upper chromosphere showing a clear link between Sun’s surface and its upper layers.
• Magnetic Influence – The discovery is important because, at these heights, the Sun’s magnetic field strongly influences the movement of plasma in the Sun’s atmosphere.
• New Technique – Instead of tracking individual sunspots or magnetic features, the team developed a novel image-correlation technique.
• Novel image-correlation technique – Used for comparing thousands of full‑disk radio images to map large‑scale plasma movement.
• Speed – Plasma moves poleward at 5–15 m/s, similar to deeper layers of the Sun.
• The plasma flow changes with the solar cycle, and at times the two hemispheres act differently based on magnetic activity.
• Magnetic link – Bright features in radio images move in step with magnetic field transport, confirming the magnetic tree hypothesis (structures high above remain connected to deeper layers like branches to roots).
• Evidence – Based on 27 years of radio observations from Nobeyama Radioheliograph.

Nobeyama Radioheliograph (NoRH) in Japan is a solar‑dedicated radio telescope array built to study the Sun’s magnetic fields and plasma.

Significance

• Solar dynamics – Shows upper atmosphere retains information about motions deep inside the Sun.
• Space weather – Understanding plasma‑magnetic field interaction crucial for predicting solar storms.
• Scientific breakthrough – Provides new tool for studying the solar dynamo (process generating Sun’s magnetic field).
• Global impact – Helps forecast events that can disrupt satellites, navigation systems, communications and power grids.

Reference

PIB | Sun