Worldwide extremely low frequency magnetic field sensor network for sprite studies

Abstract

The first measurements from a new globally distributed extremely low frequency magnetic field sensor network are presented. The recorded data demonstrate that the system observed lightning with continuing currents on a global scale with a timing accuracy of ∼30 μs. The network consists of four state of the art instruments at sites in Scotland, the United States, South Africa and Australia. Each instrument records the two horizontal magnetic field components (Bx and By) with a sampling frequency of 4 kHz. The first results show the typical electromagnetic signature of a transient airglow increase (sprite) above a thunderstorm in southern Europe which is simultaneously imaged with a video camera. A similar electromagnetic signature is recorded from a lightning discharge in central Africa, and it is also attributed to a sprite occurrence. Studies using this global network should advance lightning and sprite research considerably.