Knowledge Nugget of the day: Northern lights

Key Takeaways:

1. Auroras are essentially natural lights that appear as bright, swirling curtains in the night sky and can be seen in a range of colours, including blue, red, yellow, green, and orange. These lights primarily appear near the poles of both the northern and southern hemispheres all year round but sometimes they expand to lower latitudes.

2. When witnessed near the North, these bright and colourful lights are called Aurora Borealis, while those in the South are called Aurora Australis. They are formed due to an active interaction in space between charged solar winds and the Earth’s magnetosphere.

3. It is caused by an increase in 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.

4. 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.

5. When solar wind particles collide with oxygen, a green coloured light is produced. Interaction with nitrogen produces shades of blue and purple. It is “much like how electrons flowing through gas in a neon light collide with neon and other gasses to produce different colored light bulbs,”

6. Auroras expand to midlatitudes when the solar wind is extremely strong. This happens when the activity on the Sun’s surface goes up, leading to solar flares and coronal mass ejections (CMEs), which are ejections of large magnetic particles and plasma from the Sun’s corona.

7. In such cases, the solar wind is so intense that it can result in a geomagnetic storm, also known as a magnetic storm — a temporary disturbance of the Earth’s magnetic field. It is during a magnetic storm that auroras can be seen in the mid-latitudes.

These lights primarily appear near the poles of both the northern and southern hemispheres throughout the year, but occasionally they expand to lower latitudes. Northern lights seen in Falmouth, Maine, US. (AP)

BEYOND THE NUGGET: Solar Storms and Dark Sky Reserve

1. Intense solar storms can be harmful as they can interfere with and threaten the smooth operations of satellites operating in the Low Earth Orbit or LEO (an altitude ranging between 200-1,600km).

2. The highly energetic particle environment created by these solar storms can also induce heating in the upper atmosphere. This increases the risk of radiation hazards, causing a drag effect on satellites positioned at LEO. An excessive drag can mean satellites facing intolerable amounts of friction, which in extreme cases can ignite and burn down the satellites, ceasing their operations completely.

Dark Sky Reserve is land that is legally protected for scientific, natural, educational, cultural, heritage and/or public enjoyment purposes

3. The observation of aurora borealis in India was made from the dark sky reserve in Ladakh. A dark-sky preserve is an area, typically surrounding a park or observatory, that limits artificial light pollution. The primary objective of the dark-sky movement is generally to endorse astronomy.

4. India’s first dark-sky preserve is the Indian Astronomical Observatory (IAO), a high-altitude astronomy station in Hanle (Ladakh) and operated by the Indian Institute of Astrophysics.

5. Recently, in January 2024, Pench Tiger Reserve (PTR) in Maharashtra was designated as India’s first Dark Sky Park in India.

Previous Knowledge Nugget: Jayaprakash Narayan

(Source: Aurora in Ladakh (IE), What are northern and southern lights? Why do they occur? In Pictures  )

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