Sun’s upper atmosphere: the corona

  • August 30, 2023
  • Posted by: OptimizeIAS Team
  • Category: DPN Topics
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Sun’s upper atmosphere: the corona

Subject :Science and technology

Section: Space technology

Sun’s Corona

Nature and Location

  • The corona is the Sun’s outermost atmospheric layer.
  • It extends thousands of kilometres above the visible surface of the Sun.
  • Gradually transforms into the solar wind that permeates the solar system.
  • Envelops all planets, including Earth, in an extended atmosphere.

The Challenge of Observing the Corona

  • Corona is usually concealed due to the Sun’s overwhelming brightness.
  • Total solar eclipses provide unique opportunities to see the corona.
    • Moon temporarily blocks the Sun’s surface light, revealing the corona’s wispy, white streamers.
  • The corona’s dynamic nature leads to constant shape and size changes.

Corona’s Temperature Discrepancy

  • The corona is significantly hotter than the Sun’s surface: about 1 million °C compared to 5,500 °C.
  • The exact cause of this temperature difference is still under investigation.

Possible Explanations for Corona’s Heat

  • Nanoflares Hypothesis: Microscopic explosions (nanoflares) at the solar surface may contribute to heating.
  • Solar Tornadoes: Giant vertical plasma spirals interacting with the Sun’s magnetic field might raise temperatures.

Solar Wind and Solar Flares

  • High-speed particles in the corona create the solar wind, influencing the entire solar system.
  • Solar flares release immense energy, affecting Earth’s atmosphere, power grids, and satellite communications.
  • A special instrument called a coronagraph is used to observe the corona and monitor solar flares.
  • Space missions like NASA’s Parker Solar Probe offer crucial insights into the Sun and the corona.
  • The ISRO will launch India’s first space mission to study the sun’s atmosphere, Aditya L1, on September 2, 2023

Parker Solar Probe’s Achievements

  • Launched in 2018, the Parker Solar Probe is designed to study the Sun’s corona up close.
  • In December 2021, the probe approached the corona at a distance of 8.2 million miles, providing unprecedented data.

Magnetic Fields and Coronal Features

  • The Sun’s magnetic fields shape the corona’s appearance.
  • Coronal loops, streamers, and other features arise due to interactions between magnetic fields and charged particles.

Solar Atmosphere Layers

Photosphere: Innermost Visible Layer

  • The photosphere emits sunlight and is the lowest layer of the solar atmosphere.
  • It ranges in temperature from 6,125 to 4,125 degrees Celsius.
  • Sunspots and granules are prominent features in the photosphere.

Chromosphere: Emission of Reddish Glow

  • The chromosphere emits super-heated hydrogen, seen as a reddish glow.
  • Visible as a red rim during a total solar eclipse.
  • It may play a role in conducting heat to the corona.

Corona: Outermost Layer

  • The corona is the outermost layer, visible during total solar eclipses or with specialized instruments.
  • White streamers or plumes of ionized gas flow outward into space.
  • Temperatures in the corona can reach up to 2 million degrees Celsius.

Science and tech Sun’s upper atmosphere: the corona