Relevance: The night sky was illuminated recently by the northern lights, or aurora borealis, visible in parts of the world including the United States, Canada, the United Kingdom, Germany, and even Hanle village in Ladakh.
Explanation:
What are Auroras?
- The northern lights, or aurora borealis, are a spectacular, colourful display of light commonly seen in the night sky in the northern hemisphere.
- Auroras in the southern hemisphere are known as the southern lights, or aurora australis.
- Both the northern lights and the southern lights are polar lights, or aurora polaris, because they occur near Earth's magnetic poles.
What causes the Aurora?
- Particles from solar eruptions bombard Earth’s magnetic field and enter the atmosphere at regions called auroral ovals. These particles interact with gases in the atmosphere, creating auroras.
- Auroras are a natural interaction between the Sun and Earth's atmosphere. Our Sun generates a strong solar wind, which carries about one million tons of extremely hot plasma (electrons, protons, and other particles) away from the Sun every second. (Hence, statement 1 is correct)
- Earth’s magnetosphere acts like a shield that protects us from most of this constant solar wind, deflecting it around Earth.
- During a solar storm, such as a solar flare or coronal mass ejection, a large amount of plasma hurls through space at high speeds as part of the solar wind.
- When this extra solar energy collides with Earth’s magnetosphere, some of the electrically charged particles move down strong magnetic field lines at the North and South Poles and become trapped in Earth's atmosphere.
- These particles bounce from the North Pole to the South Pole and back again, transferring energy to molecules in Earth’s atmosphere as they go.
- The colorful, glowing lights of the aurora result when these energized molecules release their extra energy.
Why are Auroras different colors?
- Auroras occur within one of Earth’s upper atmosphere layers, the thermosphere.
- The thermosphere extends between 85-600 kilometers high. Aurora and satellites occur in this layer.
- Solar particles trapped here interact with different types of gas molecules, mostly nitrogen and oxygen, resulting in unique, colored displays of light.
- Oxygen gives off green and red light, while nitrogen glows blue and reddish-purple.
- Green-colored auroras are most frequent, resulting from interactions with oxygen molecules at lower altitudes (between 100-300 km), while the less commonly occurring red auroras form from interactions with higher altitude (above 300 km) oxygen molecules. (Hence, statement 2 is correct)
Do Auroras affect Earth?
- The only significant impact to Earth associated with auroras is a possible disruption of radio communications as charged particles from the Sun create a disturbance in Earth’s magnetic field.
- When the magnetic disturbance is particularly strong, auroras can sometimes be seen farther from the poles, in mid-latitude locations.
Other Planets have Auroras, too!
- Earth isn’t the only planet that experiences auroras. Any planet with an atmosphere and a magnetic field is likely to have auroras.
- Spectacular auroras have been observed on Saturn and Jupiter.
Therefore, option (c) is the correct answer.
Subject: Current Affairs | S&T
Level of Difficulty: Moderate | Factual
