Wave and plasma measurements on the Vega-1 and Vega-2 spacecraft in the environment of comet Halley

The Vega-1 and Vega-2 wave and plasma measurements performed on 6 and 9 March 1986 in the environment of comet Halley present similar characteristics. Field spectral intensity of up to $\text{5}\text{mVm}{}^{\mathrm{?1}}\text{Hz}{}^{\mathrm{?}}\text{1}\text{2}$ at 300 Hz is measured at closest approach; enhanced signals are detected in the whistler mode and in the vicinity of the lower hybrid resonance frequency within respective average distances of 130,000 km and 60,000 km from the nucleus. The plasma density rises from 100 cm^?3 at 200,000 km up to 3000 cm^?3 at 25,000 km. The spacecraft potential is of the order of +3 V beyond a distance of 200,000 km and decreases to about +0.5 V at 8,000 km.