Geomagnetic Storm Forecasts

The geomagnetic storm probabilities are the estimated chances of at least one 3-hour K index, at the indicated level, for each of the next 3 days.

Active: K = 4.
Minor storm: K = 5.
Major or Severe storm: K > 6.

The "K index" is a 3-hourly quasi-logarithmic local index of geomagnetic activity relative to an assumed quiet-day curve for the recording site. Range is from 0 to 9. The K index measures the deviation of the most disturbed horizontal component of the magnetic field.

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