What is a Geomagnetic Storm?
A geomagnetic storm is a temporary disturbance of Earth's magnetic field caused by the solar wind or by coronal mass ejections (CMEs). When the solar wind is fast and dense, or when a CME's magnetic field couples with Earth's magnetosphere (especially when the interplanetary field is southward), the magnetosphere is compressed and disturbed. Currents flow in the ionosphere and magnetosphere, and charged particles can enter the upper atmosphere near the poles, producing aurora. The strength of the disturbance is measured globally by the Kp index (0–9).
Causes: CMEs and Solar Wind
Most strong geomagnetic storms are caused by Earth-directed CMEs that take 1–3 days to arrive. High-speed solar wind from coronal holes can also cause recurrent storms. The orientation of the interplanetary magnetic field (IMF) is critical: a southward component allows magnetic reconnection and efficient transfer of energy into the magnetosphere.
Kp Index
The Kp index is a planetary index of geomagnetic activity from 0 (quiet) to 9 (extreme). It is derived from ground-based magnetometers. Kp 0–2: quiet. Kp 3–4: unsettled. Kp 5–6: storm. Kp 7+: severe storm. The scale is logarithmic. Cosmic Radar shows the daily Kp in the report so you can see current storm level.
Effects on Earth
Aurora: Higher Kp means aurora visible at lower latitudes. Power grids: Geomagnetically induced currents (GIC) can stress transformers. Satellites: Radiation and charging. GPS/radio: Ionospheric disturbances. Aviation: Polar routes may be adjusted. Forecasting by NOAA SWPC and others helps operators prepare. Cosmic Radar aggregates Kp, flares, CMEs, and aurora outlook in the daily report.
Sources and further reading
- NOAA – Geomagnetic storms – Storm definition, causes, and effects
- NOAA – Kp index – Planetary K-index
- ESA Space Weather – European forecasts
- NASA Magnetosphere – Earth's magnetic field