Regular noise background in VLF emission and global thunderstorm centers

VLF emissions were recorded at high latitudes by loop-antenna measurements involving the azimuth rotation of the antenna plane. Ratios of regular-noise-background (RNB) amplitudes for different antenna positions were analyzed, and it is shown that the received radiation can be approximated by a model of two sources, one of which is localized while the other is 'isotropic' with respect to the azimuth. The azimuth angles of radiation arrival from localized sources are examined in detail, and a formula is obtained for the azimuth of signal arrival. An analysis of data obtained in autumn-winter periods at different measurement points shows that localized RBN sources are global thunderstorm centers.