In the present paper a model is described of the lightning discharge that was developed in the USSR by Stekolnikov in 1940s. This model is practically unknown to specialists in the atmoshperic electricity. We describe its parameters and compare these with the data commonly used in the literature. Computations show that SM remains up to date and is consistent with the modern concepts.
The ELF data during one year (July 15 – September 27, 2004 and October 1, 2005 to June 30) at a single station of Moshiri (Japan) are used to investigate the global distribution and characteristics of intense lightning discharges. The statistics of those ELF transients whose locations are sufficiently accurately determined, has yielded the following; (1) Enhanced activity is found in Asia (for both polarities), and small charge moment change (Qds) events are dominant in Asia, (2) Large Qds (≥500C·km) is dominant in Africa and America, with Qds >1000C•km being predominant in Africa. (3) Continents are rich in +CGs, while –CGs are dominant in the maritime Asia, and (4) The UT (universal time) dependence of occurrence rate of intense ELF transients is found to be completely in opposite phase to that of conventional worldwide thunderstorm activity, being concentrated in the UT interval from 20 h to 5 h.
In order to detect seismo-related patterns that manifest themselves in fractal properties of ULF magnetic field variations, the fractal and multifractal analyses of the ULF data obtained from several stations were performed. As a result, two different behaviors of fractal parameters of the ULF magnetic field variations were detected. The first one has the certain co-seismic character and manifests itself in significant increase in fractal dimension synchronous with the rise of seismic activity. Another pattern can be interpreted as a manifestation of the seismic preparation processes, which is characterized by the significant gradual decrease in fractal dimension during the extended time period of several months. Also a new procedure of the local geomagnetic activity (LGA) level estimation was proposed. A correlation between the geomagnetic activity and the fractal dimension, and, consequently, the necessity of taking into a consideration the LGA level was demonstrated.
This paper was intended to find out any relation between anomalous line-of-sight propagations on VHF band and occurrences of earthquakes near the VHF propagation path. The TV broadcasting waves on the VHF band were measured continuously for 504 days, in which we assembled an automatic measurement system. The waves propagated on the line-of-sight from Tokyo Tower to Gunma Univ. in Kiryu were measured on VHF band. In order to distinguish anomalous propagation data from normal data, a statistical process is adopted in such a way that six times deviation from the mean value was adopted as a criterion for distinguishing between the anomalous or normal propagation data. In a time interval between the appearance of anomalous propagation and the occurrence of earthquake was shorter than 48 hours (2 days), the anomalous propagation was additionally recognized as being associated with the earthquake. During the observation period of 504 days, only four anomalous propagations happened and we observed three earthquakes associated with these anomalous propagations. As a result, it is found that anomalous line-of-sight propagations on VHF band might be associated with the earthquakes near the VHF propagation path.
We have observed over-horizon FM broadcasting waves at Niijima for the purpose of clarifying some relationships between earthquake activities and the propagations of over-horizon FM waves. We have monitored 81.3MHz, 79.2MHz and 82.1MHz FM broadcasting waves, from Tokyo, Shizuoka and Hamamatsu, respectively, at Niijima. The period of the observation was for 3 years from January 2005 to December 2007. From observational results, it was found that the received levels of three FM broadcasting waves had seasonal variations in their fluctuations; the fluctuation levels in summer season were larger than those in winter. And the fluctuation levels were positively correlated with the temperature and the water vapor pressure, and were negatively correlated with the atmospheric pressure and the wind speed. In the observation period, one big earthquake with seismic intensity of 4 and three earthquakes with seismic intensity of 3 were observed near the propagation path of the FM broadcasting from Tokyo. By comparing the fluctuation levels of FM waves with the seismic intensities, it was found that there was little correlation between them. It is reasonable to consider that the received level fluctuations are mainly caused by meteorological conditions not by earthquakes. It was concluded that affections of meteorological conditions should be considered to observe seismic activities through over-horizon FM broadcasting waves.
Observation of 48.25-MHz radio waves transmitted from Bangkok, Thailand, was carried out at Tateyama, Japan, during 2001. Since the radio wave propagates through a crest of equatorial anomaly, which disturbs stratified structure of the ionosphere, it is conceivable that the propagation of the radio wave is affected by three-dimensional structure of the ionosphere. Seasonal and diurnal variations of the signal intensity are quite similar to ƒ0F2 above Guangzhou and also Okinawa, which are located on the great circle path between Bangkok and Tateyama. Using ray-tracing calculations with the distribution of the electron density determined by IRI model, it is also confirmed that the radio wave propagates to Tateyama because of one-hop reflection in the ionosphere and that MUF is mainly dependent on ƒ0F2 above the midpoint between Bangkok and Tateyama. Although the value of ƒ0F2 is almost constant, MUF calculated by the ray-tracing treatment decreases around 14 JST in fall and winter. This decrease is also detected in the observational result of the signal intensity of the radio wave received at Tateyama. The ray tracing calculation shows that the decrease of MUF is due to tilt of the distribution of electron density, which is noticeable in developing the equatorial anomaly. Then discussing the propagation characteristics of 48.25-MHz radio waves crossing equatorial anomaly region, it is important to consider not only the parameters of the ionosphere, e.g. ƒ0F2, but also the tilt of the distribution of electron density.