Chromosphere|| Layers of the Sun|| UPSC Current Affairs

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Context

Using 100 years of daily records of the Sun at the Kodaikanal Solar Observatory, astronomers have succeeded in mapping, for the very first time, the variation in the rotation speed of the Sun’s chromosphere.

Read about Kodaikanal Solar Observatory: https://www.iasgyan.in/daily-current-affairs/kodaikanal-solar-observatory

Sun's Chromosphere

The chromosphere is a thin layer of the Sun's atmosphere located between the cooler photosphere below and the much hotter corona above.

This layer plays a key role in solar phenomena and is critical for understanding solar dynamics, including solar flares and other space weather events.

Read about solar flares: https://www.iasgyan.in/daily-current-affairs/solar-flares-26#:~:text=Solar%20flares%20result%20from%20the,form%20of%20heat%20and%20radiation.

The chromosphere is positioned roughly 400 to 2,500 kilometers above the photosphere. Though only a few thousand kilometers thick, it represents a transitional layer that gradually shifts from the cooler lower solar atmosphere to the much hotter corona.

Temperature

The chromosphere has a temperature gradient, with temperatures ranging from about 4,500 K at its lower boundary to 25,000 K at the upper boundary.

This is notable because, unlike the photosphere, which cools as you move outward, the chromosphere heats up as you approach the corona.

Characteristics

The chromosphere emits a reddish glow during a solar eclipse, visible around the edges of the Sun. This is due to hydrogen alpha emission lines, giving the chromosphere its characteristic color. It is typically difficult to observe in visible light unless during specific wavelengths like H-alpha.

The chromosphere is highly dynamic. It is characterized by spicules (jet-like features) and filaments (large arcs of material), both of which transport energy and material into the upper solar layers.

Magnetic fields within the chromosphere are very active and can give rise to solar flares when they interact with regions of the corona.

Energy from the Sun’s interior is transported through the chromosphere, often through waves and magnetic field interactions. This energy is essential for powering solar winds and coronal heating.

Importance

Studying the chromosphere helps scientists understand solar eruptions, which can affect space weather and even communications and power systems on Earth. Observations of the chromosphere, particularly in ultraviolet (UV) and hydrogen alpha wavelengths, helps to understand the Sun’s magnetic activity and its influence on the solar system.

Layers of the Sun

Layer	Depth/Thickness	Temperature Range	Key Characteristics	Function
*Core*	0-25% of the Sun's radius	~15 million K	Site of nuclear fusion, where hydrogen is converted into helium.	Energy production through nuclear fusion.
*Radiative Zone*	~25-70% of the Sun's radius	~7 million K to 2 million K	Energy moves outward via radiation; photons are absorbed and re-emitted.	Transports energy via radiation, taking millions of years.
*Convective Zone*	~70% to the surface (~200,000 km)	~2 million K to 5,800 K	Energy is transported through convection; hot plasma rises and cools down.	Transfers energy through convection currents.
*Photosphere*	~500 km thick	~5,500 K	Visible surface of the Sun, where light is emitted; includes sunspots.	Emits visible light; boundary between interior and atmosphere.
*Chromosphere*	~2,000-3,000 km thick	~4,500 K to 25,000 K	Reddish layer seen during solar eclipses; site of dynamic phenomena like spicules.	Transports energy and particles, transitions to corona.
*Transition Region*	~100 km thick	~25,000 K to 1 million K	Sharp temperature increase; ionized gases form plasma.	Region where energy and heat move into the corona.
*Corona*	Extends millions of km into space	~1-3 million K	Outermost layer, visible during eclipses, source of solar wind.	Drives solar wind and releases magnetic energy.

Sources:

PIB

PRACTICE QUESTION

Q:If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth?
1. GPS and navigation systems could fail.
2. Tsunamis could occur at equatorial regions.
3. Power grids could be damaged.
4. Intense auroras could occur over much of the Earth.
5. Forest fires could take place over much of the planet.
6. Orbits of the satellites could be disturbed
7. Shortwave radio communication of the aircraft flying over polar regions could be interrupted.

Select the correct answer using the code given below:

A) 1, 2, 4 and 5 only

B) 2, 3, 5, 6 and 7 only

C) 1, 3, 4, 6 and 7 only

D) 1, 2, 3, 4, 5, 6 and 7

Answer: C) 1, 3, 4, 6 and 7 only

Explanation:

Statement 1 is correct: Solar storms can interfere with the ionosphere, the layer of Earth's atmosphere that reflects radio waves. This interference can lead to inaccuracies in GPS signals, causing navigation systems to fail or provide incorrect information.

Statement 2 is incorrect: Tsunamis are primarily caused by underwater earthquakes, volcanic eruptions, or landslides, not by solar storms. While solar storms can affect Earth’s magnetic field and lead to various disruptions, they do not trigger tsunamis.

Statement 3 is correct: Solar storms can induce geomagnetic currents that may overload electrical grids. This can lead to transformer damage and widespread power outages. The 1989 Quebec blackout was a notable example where a solar storm caused significant disruptions to the power grid.

Statement 4 is correct: Solar flares release a burst of solar wind and magnetic fields into space, which can interact with Earth’s magnetic field. This interaction can enhance auroras (Northern and Southern Lights), making them visible at lower latitudes than usual.

Statement 5 is incorrect: While solar storms can cause various electrical disturbances and failures, they do not directly cause forest fires. Forest fires are typically a result of human activity or natural causes like lightning strikes.

Statement 6 is correct: Solar storms can increase the density of the Earth’s atmosphere at higher altitudes, leading to increased drag on satellites in low Earth orbit. This can cause satellites to drift from their intended orbits, requiring adjustments.

Statement 7 is correct: Solar storms can disrupt radio communications, particularly in polar regions where the effects of solar activity are strongest. High-frequency (HF) radio waves can be significantly affected, leading to interruptions in communication for aircraft.

SUN’S CHROMOSPHERE