From a statistical study of ducted whistlers observed at Halley, Antarctica
? in 1996, which had propagated on paths in the range L = 2.5-4.5, we repor
t mean occurrence rates, numbers of components per whistler, intensities, e
tc. for night and day conditions and in different seasons at solar minimum.
We found an average whistler rate of 5 min(-1) and 3 components per whistl
er. Received whistler amplitudes were measured as a function of frequency a
nd were in the range 2-40 fT, typically 10 fT at 4 kHz. Combining these res
ults with a propagation model, we estimate mean whistler duct output powers
to be around 1-10 mW, (similar or equal to 0.1-1 mJ per whistler in the 3-
5 kHz band). Inferred typical equatorial wave fields for ducted whistlers o
f 0.3 pT led to estimated radiation belt lifetimes for 1-100 keV electrons
due to,gyroresonance with ducted whistlers of 2 x 10(6) days. This compares
with published lifetimes due to plasmaspheric hiss of order 10(5) days or
less, and we conclude that, on average, lightning which enters and propagat
es in magnetospheric ducts, although known to cause pitch angle scattering
and precipitation of trapped electrons, does not significantly affect the r
adiation belt fluxes in a statistical sense. We have compared our results w
ith those from a similar study by Burgess and Inan (J. Geophys. Res. 98 (19
93) 15,643-15,665). In a separate investigation of multi-component whistler
s received in winter at quiet times, using the same methodology, we have fo
und that the duct output power generally decreases with increasing L. This
is consistent with previous theoretical work and parallels a similar experi
mental conclusion with respect to higher-frequency whistler-mode signals fr
om VLF transmitters. (C) 2000 Elsevier Science Ltd. All rights reserved.