Predicted Dst and observed (provisional) Dst over the past 24 hours

The graph shows our predictions of the Dst index (blue line) over the past 24 hours, compared with the quick-look Dst measurements subsequently recorded by the World Data Centre for Geomagnetism (WDC-C2), Kyoto, Japan (black line). View the equivalent plot for the:

• last 7 days
• last 28 days

The coloured bar on the right hand side of the graph indicates an activity level corresponding to the Dst value. Low activity is defined as Dst > -20 nT, medium activity is -20 nT > Dst > -50 nT and high activity Dst < -50 nT.

We define a magnetic storm as any interval for which Dst is less than -20 nT and during which Dst drops below -50 nT (into the high activity zone). Thus green indicates no storm, a green - amber sequence may indicate the start of a storm, but a full green - amber - red sequence is needed to identify a storm conclusively.

The magnetic storm forecast is used to produce a satellite risk forecast.