Latitudinal Variation in Sun's Rotation Speed | 28 Sep 2024

Source: PIB 

Why in News?

Recently, Indian astronomers have mapped variation in the Sun's rotation speed from its equator to its poles for the first time. 

• The study used 100 years of daily solar observations from the Kodaikanal Solar Observatory, Tamil Nadu. 

What are the Key Findings of the Study? 

• Sun's Chromospheric Rotation Mapped: Astronomers have successfully mapped the variation in the rotation speed of the Sun’s chromosphere for the first time. 
  • The chromosphere is a thin layer of plasma that lies between the Sun’s visible surface (the photosphere) and the corona (the Sun’s upper atmosphere).  
• Differential Rotation of the Sun: The Sun's equator spins much faster than its poles. It takes the equatorial region only about 25 days to complete one rotation, while the poles take 35 days. 
  • The Sun’s equator rotates at 13.98 degrees per day, while at 80 degrees latitude, the rotation rate slows to 10.5 degrees per day. 
• Contribution of Kodaikanal Solar Observatory: Using solar plages and network cells from the observatory's records of 100 years, astronomers could measure the Sun's rotation speeds across all latitudes. 
  • Plages are brighter regions with weaker magnetic fields. They are found in the chromosphere and are 3 to 10 times larger than sunspots. 
  • Network cells have weaker magnetic fields and are slightly larger than individual sunspots but smaller than sunspot groups. 
  • Unlike sunspots, plages and networks are always present on the Sun's surface, helping scientists study the rotation rate even at the poles. 
    • Sunspots are areas that appear dark on the surface of the Sun. They appear dark because they are cooler than other parts of the Sun’s surface. 
• Significance of the Findings: Understanding this differential rotation is essential as it is behind the solar dynamo, the 11-year solar cycle, and its periods of intense activity that even produce magnetic storms on Earth.

What are the Key Facts About the Sun's Atmosphere? 

• The Sun’s atmosphere consists of multiple layers, each with distinct characteristics and temperatures: 
  • Photosphere: The visible surface of the Sun, marking the boundary between the interior and the atmosphere. 
  • Chromosphere: An irregular layer above the photosphere where the temperature rises from 6000°C to about 20,000°C. 
  • Transition Region: A thin and very irregular layer of the Sun’s atmosphere that separates the hot corona from the much cooler chromosphere. 
  • Corona: The Sun’s outer atmosphere. It is much hotter than the underlying chromosphere or photosphere. 
• Beyond the corona lies the solar wind, which is an outward flow of charged particles (plasma) originating from the corona. 
  • The solar wind extends far into space affecting planetary atmospheres and causing phenomena like the auroras on Earth.