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India Witnesses Rare Aurora Lights

Context:

India, for the first time witnessed the rare aurora lights from Ladakh.

Relevance:

Prelims, GS-III: Science and Technology

Dimensions of the Article:

  1. India captures Northern lights
  2. What is a Solar flare?
  3. What is a Geomagnetic storm?
  4. What is aurora?

India captures Northern lights:

  • Recently, the Indian Astronomical Observatory above Mount Saraswati captured a rare phenomenon: A geomagnetic storm which struck Earth’s magnetic field, causing the charged particles from the sun to collide with atoms and molecules in the Earth’s atmosphere.
  • These collisions result in “Aurora” or the northern or southern lights. 
  • The regions where the aurora can be seen are Earth’s magnetic poles and regions near them.
  • The rare sightings from these sites are likely due to the fact that the Auroras extended to these lower latitudes, allowing people in these areas to witness the natural phenomenon.
  • Significance:
    • The Aurora phenomenon is a natural light show that is regarded as one of the most beautiful displays in the world.
    • The Aurora phenomenon captured in India can be used as a valuable tool for scientific research too.

What is a Solar flare?

  • A solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surface and in close proximity to a sunspot group.
  • Powerful flares are often, but not always, accompanied by a coronal mass ejection.
  • Even the most powerful flares are barely detectable in the total solar irradiance (the “solar constant”).
  • Flares are closely associated with the ejection of plasmas and particles through the Sun’s corona into interplanetary space. Solar flares also copiously emit radio waves.
  • It usually takes days for the solar plasma ejecta to reach Earth.
  • Flares also occur on other stars, where the term stellar flare applies.
  • Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior.
  • The frequency of occurrence of solar flares varies following the 11-year solar cycle.
  • If the ejection is in the direction of the Earth, particles associated with this disturbance can penetrate into the upper atmosphere (the ionosphere) and cause bright auroras, and may even disrupt long-range radio communication.

What is a Geomagnetic storm?

  • A geomagnetic storm (commonly referred to as a solar storm) is a temporary disturbance of the Earth’s magnetosphere caused by a solar wind shock wave and/or cloud of magnetic field that interacts with the Earth’s magnetic field.
  • The disturbance that drives the magnetic storm may be a solar coronal mass ejection (CME) or (much less severely) a co-rotating interaction region (CIR), a high-speed stream of solar wind originating from a coronal hole.
  • The frequency of geomagnetic storms increases and decreases with the sunspot cycle. During solar maximum, geomagnetic storms occur more often, with the majority driven by CMEs.

What is aurora?

  • An aurora, also known as the polar lights or aurora Polaris, is a natural light display in Earth’s sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic).
  • There are two types of aurora – the aurora borealis and aurora australis – often called the northern lights and southern lights.
  • Conditions to witness the aurora lights: a clear sky, no clouds, and total darkness.
  • Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals or dynamic flickers covering the entire sky.
  • Auroras are the result of disturbances in the magnetosphere caused by solar wind.
  • These disturbances alter the trajectories of charged particles in the magnetospheric plasma.
  • These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere).
  • The resulting ionization and excitation of atmospheric constituents emit light of varying colour and complexity.
  • The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles.

Why do auroras come in different colors and shapes?

  • The color of the aurora depends on which gas — oxygen or nitrogen — is being excited by the electrons, and on how excited it becomes. The color also depends upon how fast the electrons are moving, or how much energy they have at the time of their collisions.
  • High energy electrons cause oxygen to emit green light (the most familiar color of the aurora), while low energy electrons cause a red light. Nitrogen generally gives off a blue light.
  • The blending of these colors can also lead to purples, pinks, and whites. The oxygen and nitrogen also emit ultraviolet light, which can be detected by special cameras on satellites.  

-Source: Times of India


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