VLF/ELF Trimpi Receiver

A narrow-band Omega phase and amplitude logger (OPAL) receiver is operated at Halley, measuring the phase and amplitude of selected VLF transmissions. The purpose is to detect impulsive energetic particle precipitation into the ionosphere through the transient perturbations caused to sub-ionospheric VLF propagation (the Trimpi effect). It forms part of a wider network of similar receivers - OPALnet. More details and some preliminary results are given by Smith and Cotton (1990): however, the original design of receiver described there has now been enhanced so that it can receive MSK transmissions, with a resulting improvement in time resolution and signal-noise ratio (Friedel et al., 1993; Smith et al., 1993).