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Source-This post on Auroras is based on the article “Aurora Borealis: What are northern and southern lights? Why do they occur?” published in “The Indian Express” on 12th May 2024.
Why in the News?
A powerful solar storm recently caused a dazzling array of colors to light up the skies in several locations worldwide.
About Auroras
1. About Auroras: They are natural phenomena characterized by bright, swirling curtains of light that illuminate the night sky.
i) These dazzling displays manifest in various colours, including blue, red, yellow, green, and orange.
ii) It is termed aurora borealis in the north and aurora Australis in the south. They primarily occur near the poles but can occasionally extend to lower latitudes.
2. Causes of Auroras: Auroras stem from solar activity, particularly from the surface of the Sun.
i) The Sun emits a continuous stream of charged particles, predominantly electrons and protons, known as the solar wind.
ii) As this solar wind interacts with the Earth’s magnetic field, it creates a protective shield.
iii) However, some charged particles become trapped in the Earth’s magnetic field and travel along magnetic field lines to the poles.
iv) Upon reaching the upper atmosphere, these particles collide with gases, resulting in luminous flashes that illuminate the sky. Oxygen collisions produce green light, while nitrogen collisions generate shades of blue and purple.
3. Expansion to Midlatitudes: Auroras extend to midlatitudes during periods of intense solar activity.
i) Solar flares and coronal mass ejections (CMEs) increase solar wind intensity, leading to geomagnetic storms.
ii) These storms are characterized by temporary disturbances in the Earth’s magnetic field. It allows auroras to be visible in mid-latitudes.
4. Recent Events and Impact: A recent geomagnetic storm triggered by a CME led to widespread auroral displays.
i) It is classified as “extreme” by the National Oceanic and Atmospheric Administration (NOAA).
ii) This storm may affect various space-dependent operations, including GPS, radio communications, flight operations, power grids, and space exploration programs.
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