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Onset detection | Bays | FAC Location | Validity

(1) Pi2 Detection

The Pi2 pulsation closely associated with substorm onset can be detected in the real time data from the York magnetometer using the wavelet technique described in Nose et al., 1998. We apply the analysis every minute to the latest 30 minute section of the incoming data. The results give the amplitude and detection time of the various wavelet components in the data. In the example plot below the blue bars indicate Pi2 detection times with the depth of colour indicating how many individual detections were binned at a particular time as the data window moved over. The red lines show the inferred substorm onset times. These are placed where there are 2 or more minutes of Pi2 activity following 10 or more quiet minutes.

Here we see a clear isolated onset at 22:18 UT. Note that we are only attempting detection when we are on the nightside. The continuous pulsation activity during the day is often in the Pi2 frequency band and generates many spurious 'detections'.

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