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What is a magnetic storm?

A magnetic storm is a period of rapid magnetic field variation. It can last from hours to days.

Magnetic storms have two basic causes:

  • The Sun sometimes emits a strong surge of solar wind called a coronal mass ejection. This gust of solar wind disturbs the outer part of the Earth's magnetic field, which undergoes a complex oscillation. This generates associated electric currents in the near-Earth space environment, which in turn generates additional magnetic field variations -- all of which constitute a "magnetic storm."
  • Occasionally, the Sun's magnetic field directly links with that of the Earth. This direct magnetic connection is not the normal state of affairs. When it occurs, charged particles traveling along magnetic field lines can easily enter the magnetosphere, generate currents, and cause the magnetic field to undergo time dependent variation. 

Sometimes the Sun emits a coronal mass ejection at a time when the magnetic field lines of the Earth and Sun are directly connected. When these events occur, we can experience a truly large magnetic storm.

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