In order to study the formation and warnings and in studies of the triggering of evolution of the charge layer created by a corona lightning. at the ground underneath thunderclouds, we have In order to help solve these problems we developed a new system of electric field detec-have developed a system to measure the electric tion.It is composed of five self-contained field at the surface and at five levels above it. sensors designed to measure the ambient electricThe sensors aloft are designed to be suspended field at various altitudes between the surface from a tethered balloon and to transmit the data and a tethered balloon that suspends the entire by telemetry.The whole system has been built system of equipment. Each sensor can detect for the Florida 89 experiment at Kennedy Space ambient field intensities up to 150 kV/m with an Center. It can display in real time the six accuracy of 1.5 % and without any detectable superimposed field variations renewed every minuinfluence of a local corona effect on the measu-te and the vertical field profile renewed every rement. A standard shutter field mill detects the second. surface electric field. The data collected aloft are telemetered via a 400-MHz frequency band. An 2. The Tethered Balloon System adapted data processing system provides a realtime display of the multilevel evolution of the The flight aspects of the tethered balloon electric field within the first hundreds of (Figure 1), where the sensors were suspended meters above the ground. The digitized data can during the Florida 89 experiment, were managed by be used to display the instantaneous vertical the American company Lighter Than Air (LTA) of profile of field intensity on various time Florida. This stream-lined 570-m 3 helium balloon scales. is maintained in a convenient orientation to the wind even when it is fixed at a mooring system at

A laboratory experiment is performed in a cold chamber to produce microdischarges between frozen hydrometeors. A charged icicle is placed close to an uncharged one connected to a transient analyser. The electric current signature obtained during each event is then studied and characterized in function of both temperature and net charge. The existence of a transition temperature of about −15°C is detected, whereas net charge clearly governs the microdischarge characteristics. Furthermore, the radiated electric field is calculated and the spectral analysis, by means of fast Fourier transform, shows that this elementary phenomenon radiates within the VHF range. Comparisons are made with previous similar work by Chauzy and Kably (1989) on microdischarges between water drops.