The graph shows our predictions of the Dst index (blue line) over the past week, 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:
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.