Remote determination of the outer radial limit of stormtime Pc5 wave occurrence using geosynchronous satellites

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Abstract
Magnetic field data from the geostationary satellites GOES 2 and GOES 3 have shown the characteristics of stormtime Pc5 waves to vary dramatically with local magnetic field inclination angle. To investigate this effect, we scanned data from GOES 2 and GOES 3 for the twelve‐month period March 1979‐February 1980. During this time GOES 2 was at 104±4° west geographic longitude (9.6±0.4° north magnetic latitude), and GOES 3 was at 135° west geographic longitude (4.7° north magnetic latitude). 105 Pc5 events were observed at GOES 3, and 28 events at GOES 2. During the period of study, only one event was observed at GOES 2 when no waves were observed at GOES 3. Using the GOES 3 Pc5 events as a control set, we investigated the dependence of GOES 2 Pc5 occurrence on the local magnetic field inclination angle. Further, using a simple partial ring current model to produce field distortion at GOES 2, we determined the equivalent L value of GOES 2 for each 10‐minute interval during which Pc5 waves were observed at both satellites. During 93% of the Pc5 wave intervals, the local magnetic field inclination angle was less than 40°, corresponding to an outer limit of L=7.4.