G4 (Severe) Geomagnetic Storm

Why in News?

A powerful G4 (Severe) Geomagnetic Storm, caused by solar activity, has lit up the night skies with spectacular auroras visible across multiple continents.

About Geomagnetic Storms

• A geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth.
• These storms result from variations in the solar wind that produce major changes in the currents, plasmas, and fields in Earth’s magnetosphere.
• The solar wind conditions that are effective for creating geomagnetic storms are sustained (for several hours) periods of the high-speed solar wind and a southward-directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere.
• The largest such storms are associated with solar coronal mass ejections (CMEs), where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. 
• Effects:
  • It results in intense currents in the magnetosphere, changes in the radiation belts, and changes in the ionosphere, including heating the ionosphere and an upper atmosphere region called the thermosphere. 
  • These storms can heat the ionosphere, causing beautiful auroras on earth.
  • Because the ionosphere is heated and distorted during storms, long-range radio communication that relies on sub-ionospheric reflection gets affected.
  • Ionospheric expansion due to these storms can increase satellite drag and make their orbits difficult to control.
  • Satellite electronics can be damaged through the buildup and discharge of static-electric charges.
  • It can disrupt global navigation systems.
  • It can create harmful geomagnetic-induced currents (GICs)in the power grid and pipelines.

What is Solar Wind?

• It is a continual stream of protons and electrons from the sun’s outermost atmosphere, the corona. 
• These charged particles breeze through the solar system at speeds ranging from around 250 miles (400 kilometers) per second to 500 miles (800 km) per second, in a plasma state.
• Solar magnetic field is embedded in the plasma and flows outward with the solar wind.
• Different regions of the Sun produce solar wind of different speeds and densities. 

When the solar wind reaches Earth, it sends a flurry of charged particles into the magnetosphere and along Earth’s magnetic field lines, towards the poles.

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