The recent news highlights the remarkable findings of Indian astronomers from the Aryabhatta Research Institute of Observational Sciences (ARIES) and the Indian Institute of Science, Bangalore. They have offered the first-time theoretical explanation of the existence of a near-surface shear layer (NSSL), a significant feature in the Sun. ARIES is an autonomous organization operating under the Department of Science and Technology.
About Near-Surface Shear Layer (NSSL):
Apart from the differentiated rotation occurring between the equator and poles, helioseismology has unveiled another key aspect of solar activity – the Near-Surface Shear Layer (NSSL). The NSSL exists very close to the visible surface of the Sun where there is a marked change in the rotation profile of the colossal star. Situated incredibly close to the solar surface, the angular velocity within this layer decreases rapidly as the radius increases. The NSSL is widely thought to play a critical role in defining the nature of large-scale convective patterns that drive the Sun’s intricate magnetism.
Concepts of Angular Velocity and Helioseismology:
Angular velocity is the rate at which an object rotates or revolves around an axis or the rate at which the angular displacement between two objects changes over time. On the other hand, helioseismology is a technique that uses sound waves to discern what lies within the Sun.
Study Findings:
During the research, the scientists utilized an equation known as the thermal wind balance equation. This equation elucidates how the slight temperature discrepancy between the solar poles and the equator, termed as thermal wind, is balanced by the centrifugal force introduced by solar differential rotation. Understanding the dynamics of NSSL proves essential for studying several solar phenomena such as sunspot formation, solar cycles and such manifestations observed in other stars.
Understanding the Differential Rotation of the Sun:
It has been well-established that different parts of the Sun rotate at varying speeds, a phenomenon recognized as Differential rotation. The equatorial regions rotate faster than the polar areas. Over time, these irregular rotation rates of the Sun cause its magnetic field to twist and entangle. These “tangles” can generate potent localized magnetic fields.
Localised Magnetic Fields and Solar Phenomena:
These localized magnetic fields on the Sun’s surface are active regions where sunspots typically occur. Sunspots are comparatively cooler areas on the Sun’s surface (photosphere) and appear dark due to their reduced temperature. Moreover, these active magnetic regions frequently trigger extreme solar disturbances such as solar flares and coronal mass ejections (CMEs).
Last Modified: February 15, 2024