Kp Index — Aurora Activity Scale
The Kp index is the global standard for measuring geomagnetic activity on a 0–9 scale. Higher Kp means stronger aurora visible at lower latitudes — but it is only one of five factors that determine whether you will actually see northern lights tonight.
Current Kp Index
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Source: NOAA Space Weather Prediction Center. Updated every 15 minutes.
Kp Index Scale — Aurora Visibility Reference
Each Kp step roughly doubles the equatorward extent of the auroral oval. NOAA geomagnetic storm categories (G1–G5) begin at Kp 5.
| Kp | Storm Level | Aurora Appearance | Where Visible |
|---|---|---|---|
| 0–1 | Quiet | Not visible | N/A |
| 2–3 | Low Activity | Faint, near horizon | Above 65° MLAT |
| 4 | Moderate | Visible to naked eye | Above 60° (Alaska, N. Scandinavia) |
| 5 | G1 Minor Storm | Bright | Above 55° (S. Scandinavia, S. Canada) |
| 6 | G2 Moderate Storm | Overhead displays | Above 50° (N. England, N. US states) |
| 7 | G3 Strong Storm | Bright, colorful | Above 45° (Central Europe, Central US) |
| 8 | G4 Severe Storm | Widespread, intense | Above 40° (Mediterranean, S. US) |
| 9 | G5 Extreme Storm | Visible everywhere | Above 30° (Tropics) |
MLAT = Magnetic Latitude, which can differ from geographic latitude by up to 15 degrees. Use the live tracker to check the forecast for your specific location.
How the Kp Index Is Measured
Global Magnetometer Network
The Kp index is derived from 13 geomagnetic observatories located between 44° and 60° geographic latitude, distributed across Europe, North America, and Australia. Each station measures the horizontal component of Earth's magnetic field every minute.
3-Hour Averaging Intervals
Stations record the largest magnetic field deviation within each 3-hour window. These station K-indices are averaged across all 13 observatories using a standardised conversion table, producing a global Kp value eight times per day.
NOAA Real-Time Estimates
NOAA publishes estimated Kp values every minute using its own magnetometer network. These near-real-time estimates power the live widget above and most aurora apps. The official 3-hour Kp is published by the GFZ German Research Centre.
Kp Index vs AuroraMe's 5-Factor Model
Kp measures geomagnetic activity. It does not tell you whether you will see aurora tonight. Four additional factors determine real-world visibility — and any one of them can cancel a display.
Kp Index Alone
- Geomagnetic activity level
- Cloud cover at your location
- Moon phase and brightness
- Darkness stage (twilight vs night)
- Your exact magnetic latitude
High Kp during overcast skies, a full moon, or daylight hours produces zero visible aurora.
AuroraMe 5-Factor Model
- Geomagnetic activity (Kp)
- Cloud cover forecast (Open-Meteo)
- Moon phase and position
- Darkness stage (astronomical twilight)
- Your magnetic latitude threshold
All five factors must align before AuroraMe fires a push notification.
Real example: On 10 May 2024 Kp reached 9 — a G5 Extreme storm.
Observers across mainland Europe saw vivid red and green aurora, but only those under
clear skies after dark. Cities under cloud cover saw nothing despite identical Kp readings.
Get Real-Time Kp Alerts on Your Phone
AuroraMe monitors Kp around the clock and fires a push notification only when all five visibility conditions align for your exact location. No false alarms from cloudy nights or summer daylight hours.
- Storm alerts from Kp 5 upward — free
- Southward Bz early warning (aurora within 30–60 minutes)
- Custom Kp threshold per saved location — Premium
- Quiet hours so alerts never wake you
Frequently Asked Questions
What is the Kp index?
The Kp index is a global measure of geomagnetic activity on a 0 to 9 scale. It is
calculated every 3 hours from 13 magnetometer stations worldwide and published by NOAA.
Higher values mean stronger solar wind disturbances and wider aurora visibility across
lower latitudes.
What Kp index do I need to see the northern lights?
The required Kp depends on your magnetic latitude. In northern Norway or Iceland
(above 65° MLAT) aurora can appear at Kp 2–3. In southern Scandinavia or northern
Canada (around 55°) you need Kp 5 or higher. In the UK or northern US states (around 50°)
you typically need Kp 6 or higher. AuroraMe calculates your exact threshold automatically
for any saved location.
What does Kp 5 mean for aurora?
Kp 5 is classified as a G1 Minor Geomagnetic Storm by NOAA. At this level aurora
becomes bright and visible to the naked eye from locations above approximately 55°
magnetic latitude, including southern Scandinavia, Scotland, and southern Canada.
Why can I not see aurora even when the Kp index is high?
The Kp index measures geomagnetic activity only — it ignores cloud cover, moonlight,
daylight hours, and your exact magnetic latitude. Any one of these factors can prevent
aurora from being visible even during a Kp 7 storm. AuroraMe combines all five factors
into a single visibility score for your location.
How often is the Kp index updated?
The official Kp index is a 3-hour average updated eight times per day by the GFZ
German Research Centre. NOAA also publishes estimated Kp values every minute for
near-real-time monitoring. The live widget at the top of this page uses NOAA estimates.
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