Global model of plasmaspheric hiss from multiple satellite observations

We present a global model of plasmaspheric hiss, using data from eight satellites, extending the coverage and improving the statistics of existing models. We use geomagnetic activity dependent templates to separate plasmaspheric hiss from chorus. In the region 22–14 magnetic local time (MLT) the boundary between plasmaspheric hiss and chorus moves to lower L∗ values with increasing geomagnetic activity. The average wave intensity of plasmaspheric hiss is largest on the dayside and increases with increasing geomagnetic activity from midnight through dawn to dusk. Plasmaspheric hiss is most intense and spatially extended in the 200 to 500 Hz frequency band during active conditions, 400 < AE < 750 nT, with an average intensity of 1,128 pT2 in the region 05–17 MLT from 1.5 < L∗ < 3.5. In the prenoon sector, waves in the 100 to 200 Hz frequency band peak near the magnetic equator and decrease in intensity with increasing magnetic latitude, inconsistent with a source from chorus outside the plasmapause, but more consistent with local amplification by substorm-injected electrons. At higher frequencies the average wave intensities in this sector exhibit two peaks, one near the magnetic equator and one at high latitudes, 45∘ < |Λm| < 40∘, consistent with a source from chorus outside the plasmapause. In the premidnight sector, the intensity of plasmaspheric hiss in the frequency range 50 < f < 1,000 Hz decreases with increasing geomagnetic activity. The source of this weak premidnight plasmaspheric hiss is likely to be chorus at larger L∗ in the postnoon sector that enters that plasmasphere in the postnoon sector and subsequently propagates eastward in MLT.

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