What are Geomagnetic Storms?

May 15, 2024

The strongest geomagnetic storm in over two decades recently hit Earth, causing radio blackouts and extending the northern lights to the southern United States.

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.