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Live · NOAA SWPC

Geomagnetic activity

How disturbed Earth's magnetic field is, measured by a worldwide network of magnetometers and summarised three hours at a time.

The planetary K-index

Latest observed

Recent

1.33

Quiet

Very quiet; aurora confined to high polar latitudes. Below Kp 5 there is no geomagnetic storm on the NOAA scale.

Measured
2026-09-16 21:00 UTC
Type
Published index
Provider
NOAA Space Weather Prediction Center

A planetary average over the three-hour interval beginning at the stated time.

Highest forecast Kp

3.67

Unsettled

For the three-hour interval beginning 2026-09-18 00:00 UTC. A forecast, issued by NOAA — not a measurement.

Observed, estimated and predicted

NOAA publishes all three in one series and marks each row. AsteriaStar keeps that marking on every bar it draws: solid is observed, dashed outline is the interval currently in progress, hatched is forecast.

0357909-1009-1109-1209-1309-1409-1509-1609-1709-1809-1909-20
  • Observed
  • Estimated
  • Predicted
  • Kp 5 or above (storm level)

Planetary K-index (observed and forecast): 81 three-hour intervals, of which 64 are observed or estimated and 17 are NOAA forecasts. Highest observed planetary K-index 4.67, for the interval beginning 2026-09-17 03:00 UTC; no observed interval reaches storm level. Highest forecast planetary K-index 3.67, for the interval beginning 2026-09-18 00:00 UTC; no forecast interval reaches storm level.

Show these values as a table
Planetary K-index (observed and forecast): 81 three-hour intervals, of which 64 are observed or estimated and 17 are NOAA forecasts. Highest observed planetary K-index 4.67, for the interval beginning 2026-09-17 03:00 UTC; no observed interval reaches storm level. Highest forecast planetary K-index 3.67, for the interval beginning 2026-09-18 00:00 UTC; no forecast interval reaches storm level.
Interval start (UTC)KpNOAA G-levelType
2026-09-10 00:00 UTC2.67—Observed
2026-09-10 03:00 UTC2.67—Observed
2026-09-10 06:00 UTC2.00—Observed
2026-09-10 09:00 UTC2.33—Observed
2026-09-10 12:00 UTC2.33—Observed
2026-09-10 15:00 UTC1.33—Observed
2026-09-10 18:00 UTC1.00—Observed
2026-09-10 21:00 UTC2.67—Observed
2026-09-11 00:00 UTC1.33—Observed
2026-09-11 03:00 UTC3.00—Observed
2026-09-11 06:00 UTC1.67—Observed
2026-09-11 09:00 UTC2.67—Observed
2026-09-11 12:00 UTC2.33—Observed
2026-09-11 15:00 UTC1.67—Observed
2026-09-11 18:00 UTC1.00—Observed
2026-09-11 21:00 UTC2.00—Observed
2026-09-12 00:00 UTC1.33—Observed
2026-09-12 03:00 UTC2.33—Observed
2026-09-12 06:00 UTC3.00—Observed
2026-09-12 09:00 UTC2.33—Observed
2026-09-12 12:00 UTC2.00—Observed
2026-09-12 15:00 UTC1.33—Observed
2026-09-12 18:00 UTC1.00—Observed
2026-09-12 21:00 UTC1.00—Observed
2026-09-13 00:00 UTC2.33—Observed
2026-09-13 03:00 UTC3.00—Observed
2026-09-13 06:00 UTC2.00—Observed
2026-09-13 09:00 UTC0.67—Observed
2026-09-13 12:00 UTC1.33—Observed
2026-09-13 15:00 UTC1.00—Observed
2026-09-13 18:00 UTC0.33—Observed
2026-09-13 21:00 UTC0.67—Observed
2026-09-14 00:00 UTC1.00—Observed
2026-09-14 03:00 UTC2.33—Observed
2026-09-14 06:00 UTC1.33—Observed
2026-09-14 09:00 UTC2.00—Observed
2026-09-14 12:00 UTC2.67—Observed
2026-09-14 15:00 UTC4.00—Observed
2026-09-14 18:00 UTC2.67—Observed
2026-09-14 21:00 UTC2.67—Observed
2026-09-15 00:00 UTC3.00—Observed
2026-09-15 03:00 UTC2.33—Observed
2026-09-15 06:00 UTC0.33—Observed
2026-09-15 09:00 UTC0.67—Observed
2026-09-15 12:00 UTC2.33—Observed
2026-09-15 15:00 UTC0.67—Observed
2026-09-15 18:00 UTC2.00—Observed
2026-09-15 21:00 UTC3.33—Observed
2026-09-16 00:00 UTC3.67—Observed
2026-09-16 03:00 UTC3.00—Observed
2026-09-16 06:00 UTC2.33—Observed
2026-09-16 09:00 UTC1.67—Observed
2026-09-16 12:00 UTC2.33—Observed
2026-09-16 15:00 UTC1.00—Observed
2026-09-16 18:00 UTC0.67—Observed
2026-09-16 21:00 UTC1.33—Observed
2026-09-17 00:00 UTC4.00—Estimated (interval in progress)
2026-09-17 03:00 UTC4.67—Estimated (interval in progress)
2026-09-17 06:00 UTC3.67—Estimated (interval in progress)
2026-09-17 09:00 UTC3.33—Estimated (interval in progress)
2026-09-17 12:00 UTC3.33—Estimated (interval in progress)
2026-09-17 15:00 UTC3.33—Estimated (interval in progress)
2026-09-17 18:00 UTC3.33—Estimated (interval in progress)
2026-09-17 21:00 UTC3.33—Estimated (interval in progress)
2026-09-18 00:00 UTC3.67—Predicted (forecast)
2026-09-18 03:00 UTC2.00—Predicted (forecast)
2026-09-18 06:00 UTC2.00—Predicted (forecast)
2026-09-18 09:00 UTC2.67—Predicted (forecast)
2026-09-18 12:00 UTC2.67—Predicted (forecast)
2026-09-18 15:00 UTC2.67—Predicted (forecast)
2026-09-18 18:00 UTC2.67—Predicted (forecast)
2026-09-18 21:00 UTC3.00—Predicted (forecast)
2026-09-19 00:00 UTC2.67—Predicted (forecast)
2026-09-19 03:00 UTC2.00—Predicted (forecast)
2026-09-19 06:00 UTC2.33—Predicted (forecast)
2026-09-19 09:00 UTC2.33—Predicted (forecast)
2026-09-19 12:00 UTC2.33—Predicted (forecast)
2026-09-19 15:00 UTC2.33—Predicted (forecast)
2026-09-19 18:00 UTC2.33—Predicted (forecast)
2026-09-19 21:00 UTC2.67—Predicted (forecast)
2026-09-20 00:00 UTC1.67—Predicted (forecast)

The last week, observed only

NOAA's definitive observed series — no forecast values at all.

0357909-1009-1109-1209-1309-1409-1509-16
  • Observed
  • Estimated
  • Predicted
  • Kp 5 or above (storm level)

Planetary K-index (observed): 56 three-hour intervals, of which 56 are observed or estimated and 0 are NOAA forecasts. Highest observed planetary K-index 4.00, for the interval beginning 2026-09-14 15:00 UTC; no observed interval reaches storm level.

Show these values as a table
Planetary K-index (observed): 56 three-hour intervals, of which 56 are observed or estimated and 0 are NOAA forecasts. Highest observed planetary K-index 4.00, for the interval beginning 2026-09-14 15:00 UTC; no observed interval reaches storm level.
Interval start (UTC)KpNOAA G-levelType
2026-09-10 00:00 UTC2.67—Observed
2026-09-10 03:00 UTC2.67—Observed
2026-09-10 06:00 UTC2.00—Observed
2026-09-10 09:00 UTC2.33—Observed
2026-09-10 12:00 UTC2.33—Observed
2026-09-10 15:00 UTC1.33—Observed
2026-09-10 18:00 UTC1.00—Observed
2026-09-10 21:00 UTC2.67—Observed
2026-09-11 00:00 UTC1.33—Observed
2026-09-11 03:00 UTC3.00—Observed
2026-09-11 06:00 UTC1.67—Observed
2026-09-11 09:00 UTC2.67—Observed
2026-09-11 12:00 UTC2.33—Observed
2026-09-11 15:00 UTC1.67—Observed
2026-09-11 18:00 UTC1.00—Observed
2026-09-11 21:00 UTC2.00—Observed
2026-09-12 00:00 UTC1.33—Observed
2026-09-12 03:00 UTC2.33—Observed
2026-09-12 06:00 UTC3.00—Observed
2026-09-12 09:00 UTC2.33—Observed
2026-09-12 12:00 UTC2.00—Observed
2026-09-12 15:00 UTC1.33—Observed
2026-09-12 18:00 UTC1.00—Observed
2026-09-12 21:00 UTC1.00—Observed
2026-09-13 00:00 UTC2.33—Observed
2026-09-13 03:00 UTC3.00—Observed
2026-09-13 06:00 UTC2.00—Observed
2026-09-13 09:00 UTC0.67—Observed
2026-09-13 12:00 UTC1.33—Observed
2026-09-13 15:00 UTC1.00—Observed
2026-09-13 18:00 UTC0.33—Observed
2026-09-13 21:00 UTC0.67—Observed
2026-09-14 00:00 UTC1.00—Observed
2026-09-14 03:00 UTC2.33—Observed
2026-09-14 06:00 UTC1.33—Observed
2026-09-14 09:00 UTC2.00—Observed
2026-09-14 12:00 UTC2.67—Observed
2026-09-14 15:00 UTC4.00—Observed
2026-09-14 18:00 UTC2.67—Observed
2026-09-14 21:00 UTC2.67—Observed
2026-09-15 00:00 UTC3.00—Observed
2026-09-15 03:00 UTC2.33—Observed
2026-09-15 06:00 UTC0.33—Observed
2026-09-15 09:00 UTC0.67—Observed
2026-09-15 12:00 UTC2.33—Observed
2026-09-15 15:00 UTC0.67—Observed
2026-09-15 18:00 UTC2.00—Observed
2026-09-15 21:00 UTC3.33—Observed
2026-09-16 00:00 UTC3.67—Observed
2026-09-16 03:00 UTC3.00—Observed
2026-09-16 06:00 UTC2.33—Observed
2026-09-16 09:00 UTC1.67—Observed
2026-09-16 12:00 UTC2.33—Observed
2026-09-16 15:00 UTC1.00—Observed
2026-09-16 18:00 UTC0.67—Observed
2026-09-16 21:00 UTC1.33—Observed

NOAA space weather scales

Live

  • Geomagnetic storms

    None

    Geomagnetic storms — disturbance of Earth's magnetic field, which drives aurora and can affect power grids, pipelines and satellite navigation.

  • Solar radiation storms

    None

    Solar radiation storms — elevated fluxes of energetic protons, which matter for spacecraft, high-altitude aviation on polar routes, and astronauts.

  • Radio blackouts

    None

    Radio blackouts — degradation of high-frequency radio communication on the sunlit side of Earth, caused by X-rays from a flare ionising the lower ionosphere.

Observed levels for 2026-09-17, stamped by NOAA at 2026-09-17 02:38 UTC. A level of zero means the threshold was genuinely not reached — it is a measurement, not a missing value.

NOAA's three-day forecast. These are predictions, not observations: the G column is an expected level and the R and S columns are probabilities.
DateGeomagnetic (G)Radio blackout ≥ R1Radiation storm
2026-09-17G1 minor5%1%
2026-09-18None expected5%1%
2026-09-19None expected5%1%

Watches, warnings and alerts

Live

No SWPC watch, warning or alert is inside its stated validity window right now. This is a real reading of the message stream, not an absence of data.

Recently issued messages (15)
  • EXTENDED WARNING: Geomagnetic K-index of 4 expected2026-09-16 05:38 UTC · expired
  • ALERT: Geomagnetic K-index of 42026-09-16 00:34 UTC
  • WARNING: Geomagnetic K-index of 5 expected2026-09-15 18:56 UTC · expired
  • WARNING: Geomagnetic K-index of 4 expected2026-09-15 18:50 UTC · expired
  • WATCH: Geomagnetic Storm Category G1 Predicted2026-09-15 17:37 UTC
  • ALERT: Geomagnetic K-index of 42026-09-14 18:02 UTC
  • WARNING: Geomagnetic K-index of 4 expected2026-09-14 16:54 UTC · expired
  • WATCH: Geomagnetic Storm Category G1 Predicted2026-09-14 15:47 UTC
  • Space weather message EF3A2026-09-14 11:03 UTC
  • Space weather message EF3A2026-09-13 08:27 UTC
  • Space weather message EF3A2026-09-12 06:45 UTC
  • Space weather message EF3A2026-09-11 05:01 UTC
  • Space weather message EF3A2026-09-11 00:45 UTC
  • ALERT: Electron 2MeV Integral Flux exceeded 1,000pfu2026-09-10 13:06 UTC
  • CANCEL WATCH: Geomagnetic Storm Category G2 Predicted2026-09-09 21:01 UTC

What Kp measures, and what it does not

Kp is a quasi-logarithmic index derived from the range of variation seen at a network of mid-latitude magnetometer observatories over each three-hour interval, then averaged into a single planetary figure. It runs from 0 to 9 and is published in thirds.

Because it is planetary and three-hourly, it is a blunt instrument by construction. A sharp local disturbance lasting twenty minutes can barely move it, and a quiet Kp does not guarantee a quiet magnetometer anywhere in particular. It is a good summary of global conditions and a poor description of any single place.

NOAA maps Kp onto the G-scale: Kp 5 is G1, and each further whole step raises the level to G5 at Kp 9. AsteriaStar uses NOAA's own mapping rather than inventing thresholds.

Provenance

Every value on these pages is fetched from NOAA SWPC or NASA CCMC and carries the provider's own timestamp. Nothing is simulated, interpolated or filled in: when a provider cannot be reached, the panel says so and shows no number. There is no overall “space weather score” here — the agencies publish scales, and a single figure invented on top of them would be an opinion wearing NOAA's authority.

Observed Kp

Recent
Status
Recent
Kind
Published index
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 02:41 UTC
Generated by provider
2026-09-16 21:00 UTC
Provider cadence
3 h
Cached for
5 min
Treated as stale after
12 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/noaa-planetary-k-index.json

Planetary K-index (observed) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/noaa-planetary-k-index.json. Kp is defined over three-hour intervals, so a five-minute cache is two orders of magnitude finer than the quantity's own resolution.

A planetary average over three hours from a network of magnetometer stations. It says nothing about conditions at one location, and a quiet Kp does not rule out a local disturbance.

Kp forecast

Forecast
Status
Forecast
Kind
Forecast
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 02:41 UTC
Generated by provider
2026-09-17 00:00 UTC
Provider cadence
3 h
Cached for
5 min
Treated as stale after
12 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/noaa-planetary-k-index-forecast.json

Planetary K-index (observed, estimated and predicted) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/noaa-planetary-k-index-forecast.json. The forecast is reissued with the three-hourly Kp cycle; five minutes is well inside it.

Each row states whether it is observed, estimated or predicted, and AsteriaStar keeps that distinction on every point it draws. A predicted Kp is a forecast, never an observation.

NOAA scales

Live
Status
Live
Kind
Published index
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 02:41 UTC
Generated by provider
2026-09-17 02:38 UTC
Provider cadence
30 min
Cached for
5 min
Treated as stale after
6 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/noaa-scales.json

NOAA space weather scales (R, S, G) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/noaa-scales.json. SWPC regenerates the scales roughly every half hour; a five-minute cache cannot delay a change by a meaningful fraction of that.

The R (radio blackout), S (solar radiation) and G (geomagnetic) scales summarise the last 24 hours and the next three days. The forecast entries are probabilities and expected levels, not observations.

Alerts

Live
Status
Live
Kind
Observation
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 02:41 UTC
Provider cadence
5 min
Cached for
5 min
Treated as stale after
6 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/alerts.json

Watches, warnings and alerts from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/alerts.json. Alerts are issued irregularly; a five-minute cache bounds how long a newly-issued alert can be missing, while the feed itself carries each alert's real issue and validity times.

The operational message stream. Each message is plain text issued by SWPC forecasters; AsteriaStar parses the structured header fields and never renders the message as markup.

Sources & references

The primary and reference sources this topic draws on.

  • NOAA SWPCNOAA Space Weather Prediction Center

    Space-weather forecasts and alerts: aurora (OVATION), the Kp index, and the G1–G5 geomagnetic storm scale.