A 3D Interferometer-Type Lightning Mapping Array for Observation of Winter Lightning in Japan

We have developed and deployed a 3D Interferometer-type Lightning Mapping Array (InLMA) for observing winter lightning in Japan. InLMA consists of three broadband interferometers installed at stations with distance from 3 to 5 km. At each interferometer station, discone antennas were installed, forming right triangle separation 75 m along their two orthogonal baselines. The output antenna is passed through 400 MHz low-pass filter then recorded 1 GS/s 16-bit accuracy. A new method has been proposed finding solutions mapping system that multiple interferometers. Using the InLMA, we succeeded positive cloud-to-ground (CG) flash winter, particularly its preliminary breakdown (PB) process. study on individual PB pulse processes allows us infer process contains many small-scale discharges scattering height range about 150 m. These series pulses appear be continuous space, though discontinuous time. also examined return stroke CG found average speed 7.5 × 107 m/s.