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(GIST OF SCIENCE REPORTER) Differential Rotation of the Sun’s Chromosphere

(NOVEMBER-2024)

Astronomers map the differential rotation of the Sun’s chromosphere using 100 years of data from the Koidaikanal Solar Observatory.

Research: Astronomers have succeeded in mapping the variation in the rotation speed of the Sun’s chromosphere, from the equator right up to its polar regions.
Significance: The research can help give a complete picture of the Sun’s inner workings.

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).
It extends for at least 2,000 km (1,200 mi.) above the surface.
It is an irregular layer above the photosphere where the temperature rises from 6000°C to about 20,000°C. Differential Rotation of Sun
Earth spins like a rigid ball, completing a full rotation every 24 hours. This rotation is the same everywhere on Earth.
But, as it is a giant ball of plasma, different parts of the Sun rotate at different speeds, depending on their latitude. It has been known for a long time that 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 a leisurely 35 days. This difference in rotation speed is called differential rotation.
Understanding the intricacies of the variation in rotation speed, as a function of latitude as well as time, is crucial to understand the Sun itself. This is because the interaction of differential rotation with the Sun’s magnetic field is what is behind the solar dynamo, the 11 year solar cycle, and its periods of intense activity that even produce magnetic storms on Earth.

Plages, unlike sunspots, are brighter regions with weaker magnetic fields.
They reside in the chromosphere, and are significantly larger than sunspots, ranging from 3 to 10 times the size of sunspots.
Network features, on the other hand, are embedded with weaker magnetic fields and are about 30,000 km across – slightly larger than individual sunspots but smaller than sunspot groups.
Unlike sunspots, both plages and networks are continuously present across the Sun’s surface throughout the solar cycle, allowing the scientists to probe the rotation rate even at the poles.