Near-Surface Shear Layer (NSSL) of Sun
Context
- Researchers, from Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science and Technology, have for the first time given the theoretical explanation of the existence of NSSL in the Sun.
About
- It was long known the Sun’s equator spins faster than the poles.
- However, a peek into the internal rotation of the Sun using sound waves revealed the existence of an intriguing layer where the rotation profile of the Sun changes sharply.
- The layer is called as near-surface shear layer (NSSL), and it exists very close to the solar surface, where there is an outward decrease in angular velocity.
- In their study, they have used an equation called the thermal wind balance equation.
- It explains how the slight difference in temperature between solar poles and equator, called thermal wind term, is balanced by the centrifugal force appearing due to solar differential rotation.
- It was noted that if this condition is true near the solar surface, it can explain the existence of NSSL, which is inferred in helioseismology (technique of using sound waves to peek inside the Sun) based observation.
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