What are Northern and Southern Lights

What’s in today’s article?

• Why in News?
• What are Auroras?
• What is the Aurora Borealis?
• What is the Aurora Australis?
• Understanding the Northern and Southern Lights Phenomenon
• Can the Auroras Expand to Midlatitudes?

Why in News?

• Early on Saturday morning, the northern lights or the aurora borealis illuminated the night sky over Hanle village in Ladakh.
• Other places of the world, such as the US and the UK, have also reported seeing the northern lights. On the other hand, Australia and New Zealand witnessed the southern lights or aurora australis.

What are Auroras?

• An aurora is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic).
• Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering the entire sky.
• They are also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis).

What is the Aurora Borealis?

• Often called the Northern Lights, it occurs in the northern hemisphere, predominantly in regions near the Arctic Circle.
  • This includes countries like Norway, Sweden, Finland, Iceland, Canada, and Alaska.
• The northern lights result from charged particles from the sun, mainly electrons and protons, colliding with the Earth’s magnetosphere and interacting with gases in the Earth’s atmosphere.
• These collisions produce colourful displays of light, primarily in green, red and purple hues.

What is the Aurora Australis?

• Also known as the Southern Lights, it occurs in the Southern Hemisphere, primarily around the Antarctic Circle.
  • It can be seen in countries such as Australia, New Zealand, Antarctica, and parts of southern South America.
• The southern lights have the exact underlying cause as the Northern Lights, i.e., charged particles from the sun interact with the Earth’s magnetic field and atmosphere in the Southern Hemisphere, creating similar colourful light displays.

Understanding the Northern and Southern Lights Phenomenon

• They occur due to activity on the surface of the Sun. The star continuously releases a stream of charged particles, mainly electrons and protons, and magnetic fields called the solar wind.
• As the solar wind approaches the Earth, it is deflected by the planet’s magnetic field, which acts like a protective shield.
• However, some of the charged particles are trapped in the magnetic field and they travel down the magnetic field lines at the north and south poles into the upper atmosphere of the Earth.
• These particles then interact with different gases present there, resulting in tiny flashes that light up the night sky.
  • For example, when solar wind particles collide with oxygen, a green colour light is produced. Interaction with nitrogen produces shades of blue and purple.

Can the Auroras Expand to Midlatitudes?

• When the solar wind is extremely strong, auroras can expand to midlatitudes.
• This happens when the activity on the Sun’s surface goes up, leading to solar flares and coronal mass ejections (CMEs), which are essentially extra bursts of energy in the solar wind.
• In these situations, the solar wind can be so strong that it can cause a geomagnetic storm/ a magnetic storm, which is a brief disruption of the Earth's magnetic field. 
  • Geomagnetic storms can also affect space-dependent operations like Global Positioning Systems (GPS), radio and satellite communications, flight operations, power grids, and space exploration programmes.
• One such geomagnetic storm that was triggered after a CME (from the AR13664 region of the sun) struck the Earth was the cause of the recent aurora events that were observed in many regions of the world.

 Q.1. What are coronal mass ejections (CMEs)?

A CME is a significant ejection of magnetic field and accompanying plasma mass from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity.

Q.2. What is the Hanle Dark Sky Reserve (HDSR)?

The HDSR, spanning an area of approximately 1,073 square kilometers, was recently designated by the Union Territory of Ladakh to control man-made light pollution and preserve the area's dark skies.

Source: Severe solar storm triggers rare auroral arc in Ladakh sky

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