In News:

• A major advancement in solar physics has been achieved with the first direct detection of small-scale torsional Alfvén waves in the Sun’s corona.
• The discovery, enabled by the Daniel K. Inouye Solar Telescope (DKIST) and its Cryogenic Near Infrared Spectropolarimeter (Cryo-NIRSP), provides crucial evidence toward solving a long-standing mystery: why the solar corona is millions of degrees hotter than the Sun’s surface.

Understanding Alfvén Waves

• Alfvén waves are low-frequency, transverse electromagnetic waves that travel along magnetic field lines in a plasma.
• They arise from the interaction between electric currents and magnetic fields within conducting plasma.
• First proposed by Hannes Alfvén (1942), after whom they are named.
• Previously, only large, sporadic Alfvén waves linked to solar flares were observed; detection of subtle, continuous coronal waves had remained elusive.

Solar Heating Problem

• Photosphere temperature: ~5,500°C (10,000°F).
• Coronal temperature: ~1.1 million°C (2 million°F).
• The mechanism by which energy moves from the relatively cooler surface to the super-heated corona has been unclear for decades.
• Proposed contributors include:
  • Magnetic reconnection
  • Alfvén wave heating

Breakthrough Observations Using DKIST

• DKIST in Hawaii is the world’s largest ground-based solar telescope (4-m mirror).
• Its Cryo-NIRSP instrument enables imaging of coronal plasma motions using Doppler shift signatures.
• Researchers identified distinct red and blue Doppler shifts, confirming twisting, torsional Alfvén waves in the corona.
• These observations provide:
  • First direct evidence of small-scale, persistent Alfvén waves.
  • Proof that such waves are pervasive across the solar atmosphere.

Significance of the Findings

• Coronal Heating Mechanism
  • The study suggests Alfvén waves may supply at least 50% of the energy required to heat the corona.
  • Their energy transport is now supported by direct observational data rather than assumptions.
• Role of Magnetic Reconnection
  • DKIST findings indicate that magnetic reconnection and Alfvén wave activity frequently occur together. Both mechanisms likely contribute to:
    • Coronal heating
    • Solar wind acceleration (>1 million mph)
• Scientific and Predictive Implications: Improved understanding of:
  • Solar atmospheric dynamics
  • Short-term solar wind behaviour
  • Long-term stellar evolution
• Enhances ability to forecast solar activity with implications for space weather and planetary environments.