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Onset detection | Bays | FAC Location | Validity

(3) Locating the Field Aligned Currents

Figure 1 shows the how the observed H and D component deflections vary with geomagnetic longitude. The red points and curve are from the lower latitude stations YOR, GML, KVI, NUR and BOR, while the blue points and curve are from the higher latitude sites FAR, NOR and OUL. Comparing the results with Figure 2 we can infer that the upward FAC is sensed somewhere between the longitudes of YOR and NUR.

H Summary

Figure 1: Variation of bay deflection (nT) with geomagnetic longitude.

SCW ground response

Figure 2: Idealised ground response

In this example we have a clear and isolated substorm onset giving a result which is consistent with part of the substorm current system being within the SAMNET sector. In general however, care must be taken in the use and interpretation of the results. Some discussion of the factors to take into account to assess the validity of the results can be found next.

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