Development of an automatic procedure to estimate the reflection height of tweek atmospherics
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2008
Received: 15 February 2008
Accepted: 8 May 2008
Published: 8 September 2008
This paper presents an automated procedure to estimate apparent reflection height h (from the cutoff frequency for the first waveguide mode, fc), horizontal propagation distance d, and propagation time Tg of tweek atmospherics. Tweek data recorded at the Kagoshima Observatory (31.48°N, 130.72°E), Japan, were used to evaluate the procedure by comparing the results estimated by the automatic method to those read manually by an operator. The two types of results showed differences (automatic–manual) of +0.58 km, −9.9 Hz, and +3058.9 km for mean h, fc, and d, respectively. The difference in h(fc) was less than the resolution of the fast Fourier transform used to obtain the tweek spectra. These comparisons indicate that the automatic estimation procedure of tweek parameters developed in this paper performs well and is a useful tool for studying long-term height variations of the ionospheric D and lower E regions using very low frequency (VLF) and extremely low frequency (ELF) records observed in Japan over the past 30 years.