Diurnal dependence of ELF/VLF hiss and its relation to chorus at L = 2.4

We present the observation and analysis of all very low frequency (0.3–10 kHz) chorus and hiss emissions observed at Palmer Station, Antarctica (L = 2.4), from January through October 2003, near the peak of the most recent solar cycle. We classify three separate categories of emissions: chorus occurring without the presence of hiss (“chorus only”), hiss occurring without the presence of chorus (“hiss only”), and chorus and hiss occurring simultaneously (“chorus with hiss”). We find that observed chorus only and chorus with hiss emissions are confined to the dawn sector, below 6 kHz in frequency. Observed hiss only emissions are confined to the dusk sector, below 4 kHz in frequency. We conclude that there are at least two distinct types of hiss observed at Palmer Station: hiss that is observed with chorus in the dawn sector and hiss that is observed without chorus in the dusk sector. The correspondence of dawn chorus with dawn hiss suggests that these two emissions are strongly related to each other, while the frequency spectrum and local time distribution of dusk hiss, coupled with the absence of simultaneous chorus, suggest that dusk hiss may be generated by terrestrial lightning.