Abstrakt
A ground-based version of the IME-HF analyzer, developed for the French TARANIS mission, was connected to a magnetic loop antenna and used for broadband measurements of lightning-induced signals in the frequency range from 5 kHz to 36 MHz. A sampling frequency of 80 MHz allows examining submicrosecond timing properties of recorded horizontal magnetic-field waveforms related to different lightning phenomena.
The instrumentation is placed in a quiet electromagnetic environment of an external measurement site of the Laboratoire Souterrain a Bas Bruit (LSBB) on the summit of La Grande Montagne (1028 m, 43.94N, 5.48E). We present results of measurements recorded during two years of operation.
We concentrate our attention on signals radiated by in-cloud processes which are difficult to detect in situ or optically. We also analyze a fine structure of the magnetic-field waveforms from different types of return strokes in order to investigate currents flowing in the lightning channels.
After the launch of the TARANIS satellite the ground-based measurements will complement the observations from space.