Context:
Recently, astronomers from the Indian Institute of Astrophysics (IIA), Bengaluru have successfully mapped the differential rotation of the Sun’s chromosphere using a century’s worth of data from the Kodaikanal Solar Observatory.
More on the News:
- This study highlights that the Sun’s equatorial region rotates significantly faster than its polar regions, taking only about 25 days for a full rotation compared to 35 days at the poles.
- Such findings are crucial for understanding solar dynamics and their effects on Earth.
- Figure: This schematic illustrates the Sun’s differential rotation, where surface regions at various latitudes rotate at different speeds.
About the Research:
Mapping Differential Rotation:
- The research utilized daily records maintained over 100 years at the Kodaikanal Solar Observatory, one of only two global observatories with such extensive solar data.
- This extensive dataset allowed researchers to analyze solar features like plages and network cells, providing insights into the Sun’s rotational behaviour.
Indian Institute of Astrophysics:
- Established in 1786 in Madras (now Chennai), it became an autonomous institute in 1971 and is headquartered in Bengaluru.
- Its main observing facilities are located at Kodaikanal, Kavalur, Gauribidanur and Hanle.
Significance of Chromospheric Features:
- Plages and network cells are critical components in this study. Unlike sunspots, which are transient and limited in latitude, these features are consistently present across the solar surface, allowing scientists to measure the rotation rate even at the poles.
- Plages 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 cells are convective structures with weaker magnetic fields and are about 30,000 km across. They are slightly larger than individual sunspots but smaller than sunspot groups.
- Their analysis revealed a clear pattern of differential rotation, with rotation rates of approximately 13.98 degrees per day at the equator and 10.5 degrees per day near the poles.
Earth vs. Sun’s Rotation:
- Earth’s Rotation: Earth rotates as a rigid body, completing a full rotation every 24 hours, uniformly across all locations.
- Sun’s Differential Rotation: Unlike Earth, the Sun rotates at different speeds depending on the latitude. The Sun, being a giant ball of plasma, exhibits differential rotation i.e. it rotates faster in the equatorial region and slower at the poles
Importance of Differential Rotation:
- The Sun’s differential rotation is crucial for understanding its internal dynamics because it drives the solar dynamo, responsible for the 11-year solar cycle.
- This interaction between differential rotation and the Sun’s magnetic field leads to periods of intense solar activity, such as solar flares and magnetic storms, which can impact Earth’s space environment.
Sun’s Atmospheric Layers
The sun’s atmosphere is made up of several layers, mainly the photosphere, the chromosphere and the corona:
1.Photosphere
- Description: The visible surface of the Sun that emits light.
- Thickness: About 500 kilometers (310 miles) thick.
- Temperature: Approximately 5,500°C (9,932°F).
2. Chromosphere
- Description: The layer above the photosphere, visible during solar eclipses.
- Thickness: About 2,000 kilometers (1,240 miles) thick.
- Temperature: Ranges from 4,500°C (8,132°F) at the bottom to around 20,000°C (36,032°F) at the top.
3.Corona
- Description: The outermost layer of the Sun’s atmosphere, visible during a total solar eclipse.
- Thickness: Extends millions of kilometers into space.
- Temperature: Extremely hot, ranging from 1 to 3 million °C (1.8 to 5.4 million °F).
Features:
- Solar Wind: Streams of charged particles (mostly electrons and protons) that flow outward from the Sun.
- Coronal Mass Ejections (CMEs): Massive bursts of solar wind and magnetic fields rising above the solar corona or being released into space.