A Statistical Study on the Dependence of Characteristics of VLF/LF Terminator Times on the Propagation Direction

Abstract

We present a detailed statistical study over two years on the times of amplitude minima (so-called terminator times) observed for the VLF/LF transmitters NPM/NWC/JJY as received at three sites. We analyzed three paths: East-West long propagation path, North-South long propagation path and North-South short propagation path. In this paper we examine the statistical behavior on the dependence of VLF/LF terminator time characteristics on the propagation direction and also we focus on the short-term terminator time (TT) characteristics. We found from the data analysis that TT behavior is regularly influenced by the lower-ionospheric condition which depends on the sunrise/sunset transition and season.