Acoustic Shocks in the Solar Chromosphere

Aspirant IAS Academy
Context: A new study has found that bright grains observed in the chromosphere of the Sun are due to upward propagating shocks in the solar plasma, and show higher temperature enhancements than previous estimates. About the Study:
  • It is led by the astronomers at the Indian Institute of Astrophysics (IIA), a team of Solar physicists from India, Norway, and the USA.
    • IIA is an autonomous institute of the Department of Science & Technology (DST), Govt. of India.
  • Findings: 
    • Have quantified the temperature enhancements during these acoustic shock events.
    • They have found that bright grains observed in the chromosphere of the Sun are due to upward propagating shocks in the solar plasma, and show higher temperature enhancements than previous estimates.
  • Significance: The study can help improve understanding of the mechanism of heating of the chromosphere situated between the bright solar surface and the extremely hot corona.
About Chromosphere:
  • The chromosphere is a highly active layer within the solar atmosphere and plays a crucial role in transferring energy (specifically non-thermal energy) that heats the corona and fuels the solar wind, which extends outward into the surrounding regions of the solar atmosphere.
  • Although a large portion of this energy is converted into heat and radiation, only a small fraction is actually used to heat the corona and power the solar wind.
Ways through which energy is transmitted from the lower layers to the higher regions of the solar atmosphere?
  • Through rearrangement of the magnetic field lines, transitioning from higher to lower potential.
  • Through propagation of different types of waves including acoustic waves.
What are acoustic shock waves?
  • Acoustic shock waves are heating events in the chromosphere that appear as transient brightening in images and are called grains.
  • The amount of energy these acoustic waves carry and how it heats the chromosphere is of fundamental interest in solar and plasma astrophysics.
Layers of the Sun:
  • The layers of the Sun are divided into two larger groups, the outer and the inner layers.
  • The outer layers are the Corona, the Transition Region, the Chromosphere, and the Photosphere, while the inner layers are the Core, the Radiative Zone, and the Convection Zone.
Outer layers of Sun other than Chromosphere 
  • Corona: It is the outermost one.
    • It starts at about 1300 miles above the photosphere, and its temperature is measured to be around 900,000 degrees Fahrenheit.
    • It is impossible to see the Corona with the naked eye
  • Transition region: Corona is followed by the Transition region, which is an extremely narrow layer that divides the Chromosphere from the Corona.
    • Its width is only 60 miles. Its layer marks the spot where the temperatures rise tremendously since the Corona layer is much hotter than the Chromosphere.
  • Photosphere: The Photosphere is the last, innermost layer of the outer layers of the Sun which can be observed directly, and its temperatures vary between 11,000 and 6,700 degrees Fahrenheit.
    • The majority of this layer is covered by granulation, which is caused by bubbling gases and sunspots from magnetic fields.
Inner Layers of the Sun:
  • Convection Zone: It is the outermost one which completely surrounds the next layer, the Radiative zone.
    • In this layer, all of the hot material found near the center of the Sun rises cools down and drops back into the radiative zone to get more heat.
    • This is the movement that creates sunspots and solar flares. This layer marks the border of what we usually refer to as the Sun.
  • Radiative Zone: It is the second inner layer of the Sun. It sits outside of the core, and it holds its extremely high temperature.
    • The zone itself has a temperature of around 7 million degrees Fahrenheit.
    • This layer serves as a passage for all the energy that is released by the core.
    • Photons travel through the radiative zone, and they can’t travel through long ranges of space, so it takes almost 50 million years for a photon to travel through this layer of the Sun.
  • Core:  It is the innermost layer of the Sun. The core is plasma, but its movement is extremely similar to that of a gas.
    • The temperature of the core of the Sun is around 27 million degrees Fahrenheit.
    • In the core, nuclear reactions occur that create helium from hydrogen atoms.
    • This releases huge amounts of energy, and it starts to move outwards toward the other layers. This energy eventually becomes the light and heat we receive on Earth.
News Source: PIB, World atlas
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