Space weather
The Sun continuously sends a stream of particles that deforms the Earth's magnetic field. When that stream surges, power grids suffer induced currents, satellites see their orbits dragged and their electronics disturbed, high frequency communications degrade at high latitudes, and aurorae move towards the equator.
2.00
Kp index at the last reading
386
km/s, solar wind speed
1.0
nT, Bz component of the field (Bt 5.0)
97
10.7 cm radio flux, in sfu
Planetary Kp index over seven days
Kp measures the agitation of the Earth's magnetic field on a scale of 0 to 9, from the readings of a worldwide network of observatories. Below 4, the field is quiet or slightly unsettled. From 5 upwards, NOAA opens its geomagnetic storm scale, G1 to G5.
| Measure | Value | Reading |
|---|---|---|
| Latest Kp | 2.00 | 20 Sept 2026, 06:00 |
| Highest Kp over the period | 4.00 | 14 Sept 2026, 15:00 |
| Readings above the storm threshold | 0 / 59 | over 7 days |
The Sun and interplanetary space
These four quantities are snapshots, not series: they are the latest readings published by NOAA at the time of the refresh.
| Quantity | Value | What it means | Reading |
|---|---|---|---|
| Solar wind speed | 386 km/s | 300 to 400 km/s when quiet. Beyond 600, a coronal hole or a mass ejection is sweeping past the Earth. | 20 Sept 2026, 09:18 |
| Interplanetary magnetic field | Bt 5.0 nT, Bz 1.0 nT | Bz is what matters: clearly negative, it opens the Earth's field and lets the solar wind's energy in. | 20 Sept 2026, 09:18 |
| 10.7 cm radio flux | 97 sfu | The reference measure of solar activity since 1947. Around 70 at cycle minimum, above 200 at maximum. | 19 Sept 2026, 20:00 |
| Strongest flare over 6 hours | C1.1 | Class of the soft X-ray flux measured by GOES. Each letter is a factor of ten: A, B, C, M, then X. | 20 Sept 2026, 05:18 |
NOAA bulletins over seven days
The prediction centre issues a watch when a phenomenon becomes likely, a warning when it is expected, an alert when a threshold is crossed, and a summary once the episode is over. Titles are those of the source.
| Bulletin | Product code | Issued |
|---|---|---|
| EXTENDED WARNING: Geomagnetic K-index of 4 expected | 16 Sept 2026, 05:38 | |
| ALERT: Geomagnetic K-index of 4 | 16 Sept 2026, 00:34 | |
| WARNING: Geomagnetic K-index of 5 expected | 15 Sept 2026, 18:56 | |
| WARNING: Geomagnetic K-index of 4 expected | 15 Sept 2026, 18:50 | |
| WATCH: Geomagnetic Storm Category G1 Predicted | 15 Sept 2026, 17:37 | |
| ALERT: Geomagnetic K-index of 4 | 14 Sept 2026, 18:02 | |
| WARNING: Geomagnetic K-index of 4 expected | 14 Sept 2026, 16:54 | |
| WATCH: Geomagnetic Storm Category G1 Predicted | 14 Sept 2026, 15:47 | |
| CONTINUED ALERT: Electron 2MeV Integral Flux exceeded 1,000pfu | 14 Sept 2026, 11:03 |
Source and freshness
Every figure on this page comes from the NOAA Space Weather Prediction Center, the United States oceanic and atmospheric agency. They are requested by our servers and cached for fifteen minutes: your browser never calls NOAA.
The Kp index is published every three hours and covers seven days here. Solar wind speed, magnetic field and radio flux are latest readings, published continuously. The flare class is computed from the 0.1 to 0.8 nanometre X-ray flux measured by the GOES satellite, over the past six hours.
These readings are provided for information only. For any operational use, power grid, polar aviation, amateur radio or satellite operations, only NOAA's official bulletins are authoritative.