ROCKET AND BALLOON OBSERVATIONS OF ELECTRIC-FIELD IN 2 THUNDERSTORMS

Instruments that measure the intense electric field strengths in thund erclouds (similar to 100 kV m(-1)) are designed to minimize the produc tion of ions by small electrical discharges (coronas) emanating from t he instruments themselves. The nearby charge of these ions would unpre dictably disturb the natural field of the cloud. In an attempt to asse ss this disturbance, two different instruments (one carried by a rocke t and one carried by a balloon) were launched on two occasions into th understorms. In spite of differing-trajectories, the soundings were si milar, which gives us some confidence in both instruments. In addition , the measurements revealed some interesting features of the two storm s. Each storm appeared to have six significant and distinct regions of charge. The balloon soundings also revealed that lightning flashes te mporarily increased the electric field strength above the thundercloud s (at altitudes from 9.7 to 14.3 km) by amounts up to 10 kV m(-1), aft er which the fields decayed away in 50 to 125 a. One pair of ascent an d descent rocket soundings, separated in time by a maximum of 60 s and horizontally by 1 to 3 km, showed Little change in the thunderstorm e lectric field between ground and 7.5 km altitude.