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solar quiet-day variation
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solar quiet-day variation

geomagnetism
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Quick Summary

The solar quiet-day variation, or Sq, refers to the regular, predictable changes in Earth's magnetic field observed on days with minimal solar activity. These variations are primarily caused by electric currents flowing in the ionosphere, a region of Earth's upper atmosphere.1

The Ionospheric Dynamo

Sunlight ionizes atmospheric particles, creating the ionosphere. Differential heating by the Sun causes atmospheric flow, which, interacting with Earth's magnetic field, generates electric currents. This system is known as the ionospheric dynamo.1

Observing Sq

By observing the daily magnetic field changes from the ground, scientists can deduce the pattern of these ionospheric currents. On quiet days, these variations follow a systematic pattern dependent on local time and latitude, forming the Sq variation. This pattern typically involves two current vortices circulating around magnetic latitudes of approximately ±30°.1

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4 Britannica Sources
  1. geomagnetic field - The ionospheric dynamo
  2. geomagnetic field - Cause of magnetic storms
  3. eclipse - Uses of eclipses for astronomical purposes
  4. geomagnetic field - Growth phase

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