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Geomagnetic storms: the Kp index

The Kp index shows how strongly the Earth's magnetic field is disturbed, from 0 to 9, for each three hours; from Kp 5 it is a geomagnetic storm. Measured values and NOAA's forecast, in Tbilisi time.

Forecast as of Nov 2, 19:14

Now, 19:00–22:00: Kp 2

No storm

For the three hours in progress the page shows NOAA's forecast; the measured value comes when they end.

No geomagnetic storm expected in the next 24 hours

For each three hours

Filled bars are measured, outlined bars are NOAA's forecast. The highlighted hour marks the three hours in progress, and the dashed line Kp 5, where a storm begins. Each bar is three hours, from the hour beneath it.

Yesterday · Sun, Nov 1

Up to Kp 5 · G1, minor storm

  1. 01:00–04:00: Kp 4, No storm, measured
  2. 04:00–07:00: Kp 5, G1, minor storm, measured
  3. 07:00–10:00: Kp 4, No storm, measured
  4. 10:00–13:00: Kp 3, No storm, measured
  5. 13:00–16:00: Kp 3, No storm, measured
  6. 16:00–19:00: Kp 3, No storm, measured
  7. 19:00–22:00: Kp 2, No storm, measured
  8. 22:00–01:00: Kp 3, No storm, measured

Today · Mon, Nov 2

Up to Kp 3 · No storm

  1. 01:00–04:00: Kp 2, No storm, measured
  2. 04:00–07:00: Kp 1, No storm, measured
  3. 07:00–10:00: Kp 2, No storm, measured
  4. 10:00–13:00: Kp 3, No storm, measured
  5. 13:00–16:00: Kp 2, No storm, measured
  6. 16:00–19:00: Kp 2, No storm, forecast
  7. 19:00–22:00: Kp 2, No storm, forecast
  8. 22:00–01:00: Kp 2, No storm, forecast

Tomorrow · Tue, Nov 3

Up to Kp 2 · No storm

  1. 01:00–04:00: Kp 2, No storm, forecast
  2. 04:00–07:00: Kp 2, No storm, forecast
  3. 07:00–10:00: Kp 2, No storm, forecast
  4. 10:00–13:00: Kp 2, No storm, forecast
  5. 13:00–16:00: Kp 1, No storm, forecast
  6. 16:00–19:00: Kp 1, No storm, forecast
  7. 19:00–22:00: Kp 1, No storm, forecast
  8. 22:00–01:00: Kp 2, No storm, forecast

Wed, Nov 4

Up to Kp 2 · No storm

  1. 01:00–04:00: Kp 1, No storm, forecast
  2. 04:00–07:00: Kp 2, No storm, forecast
  3. 07:00–10:00: Kp 2, No storm, forecast
  4. 10:00–13:00: Kp 2, No storm, forecast
  5. 13:00–16:00: Kp 1, No storm, forecast
  6. 16:00–19:00: Kp 1, No storm, forecast
  7. 19:00–22:00: Kp 1, No storm, forecast
  8. 22:00–01:00: Kp 1, No storm, forecast

What the levels mean

NOAA's geomagnetic storm scale, G1 to G5, by the three-hour Kp index:

  • Kp 0–4: No storm
  • Kp 5: G1, minor storm
  • Kp 6: G2, moderate storm
  • Kp 7: G3, strong storm
  • Kp 8 and 9−: G4, severe storm
  • Kp 9: G5, extreme storm

NOAA gives Kp in thirds: 4.67 is 5−, 5.33 is 5+. The page shows it as a whole number, as the scale counts it: 5−, 5 and 5+ are all Kp 5, a G1 storm.

NOAA gives a value for each three hours of UTC. Tbilisi is 4 hours ahead, so the page's days start at 01:00, and its slots at 01:00, 04:00, 07:00 and so on.

NOAA's forecast covers today and the next two days and is updated twice a day. The hours to come show its forecast, the hours past the measured value, which comes as each three hours end; the latest values are preliminary.

NOAA describes storms by their effects on power grids, satellites, radio and satellite navigation, and by how far from the poles the aurora can be seen.

Data: NOAA's Space Weather Prediction Center (SWPC), US government information in the public domain; the times are converted to Tbilisi time and the values rounded by this site.