Transient Electric Field in the Mesosphere above a Γ-shape Lightning Stroke     

Irina G. Kudintseva  Alexander P. Nickolaenko  Masashi Hayakawa 《Surveys in Geophysics》2010,31(4):427-448

We describe the space–time distribution of the pulsed electric field in the middle atmosphere above a positive Γ-shaped lightning stroke. The channel of such a discharge contains a vertical and a horizontal section. The current wave moves initially vertically and then turns horizontally so that radiation appears from the vertical electric dipole followed by that from the horizontal dipole. Combined with reflection from the perfectly conducting ground, the source provides three subsequent pulses in the atmosphere, with the lag being determined by the finite velocity of the current wave in the Γ-shaped stroke. The pulses are reproduced by reflections from the air-ground and the air-ionosphere interfaces and the waveform resembles the M-component, which is often noted in the negative strokes (e.g. Yashunin et al., J Geophys Res 112:D10109, 2007). The non-stationary fine structure appears in the spatial distribution of electric field, which persists for 2 ms or even more and exceeds the runaway electron threshold. Estimates support the idea of free electron bunching in the mesosphere by the pulsed electric field. Focusing may occur about 10 km away from the point of electron- field interaction; it is delayed by a few ms from the moment of interaction. The data presented might be helpful in realistic modeling of the red sprite formation.  相似文献   

Shaking Maps for Scenario Earthquakes by Applying the Upgraded Version of the Strong Ground Motion Prediction Method ��Recipe��     

Nobuyuki Morikawa  Shigeki Senna  Yuzuru Hayakawa  Hiroyuki Fujiwara 《Pure and Applied Geophysics》2011,168(3-4):645-657

The strong ground motion prediction method ??Recipe?? was published by the Headquarters for Earthquake Research Promotion (HERP) of Japan. HERP has applied this method to prepare shaking maps for scenario earthquakes in specific active faults. Recently, Recipe was updated following its verification by simulations of strong ground motions associated with the Mw?=?6.6 off-shore earthquake west of Fukuoka prefecture in 2005, which occurred in the northwest part of the Kego fault zone located in northern Kyushu, Japan. One of the prominent changes in the upgraded version of Recipe is the inclusion of a procedure to evaluate seismic intensities on the ground surface from waveforms of S-wave velocity of 400?m/s on the engineering bedrock. By applying the upgraded version of Recipe, we have made shaking-maps for earthquakes in the southeast part of the Kego fault zone, which is located directly below the mega-city of Fukuoka. We assume four source models for scenario earthquakes; the locations of the asperities and the hypocenters vary between the models. The results show that in all cases, disastrous seismic intensities can strike a wide area of Fukuoka city. Differences in the distributions of seismic intensities among the four cases can be clearly observed in the area located on the extension of the source fault. Furthermore, we construct a velocity-layer structure model on the engineering bedrock for the central area of Fukuoka city. We assess not only the distribution of seismic intensities but also waveforms on the ground by using an equivalent linear method for the central area of Fukuoka city.  相似文献   

A study of the morphology of winter sprites in the Hokuriku area of Japan in relation to cloud charge height     

K. Myokei  Y. Matsudo  T. Asano  T. Suzuki  Y. Hobara  K. Michimoto  M. Hayakawa 《Journal of Atmospheric and Solar》2009,71(5):597-602

Continuous observations of sprites in the Hokuriku area of Japan were performed from two optical sites during the three winter periods. The purpose of this observation is to study the major effect in the appearance of sprites and in determining the morphology of sprites (columns or carrots). Detailed analysis is performed based on the estimation of the height of ?10 °C at the time of sprite occurrence. When the height of ?10 °C is lower than 1800 m, the occurrence of sprites is infrequent, and the dominant shape is column. Then when it is increased (1800–3000 m), a new situation takes place, namely the occurrence of sprites is very enhanced and more spectacular shapes like carrots tend to be frequently observed in addition to column sprites. These sprite characteristics are first compared with those of parent lightning in the Hokuriku area and with our latest computer simulations on sprite initiation.  相似文献   

Three-dimensional EM computer simulation on sprite initiation above a horizontal lightning discharge     

T. Asano  T. Suzuki  M. Hayakawa  M.G. Cho 《Journal of Atmospheric and Solar》2009,71(8-9):983-990

The purpose of this paper is to study the three-dimensional (3D) effects of the source current and the electromagnetic (EM) pulse on the distribution of upper atmospheric electric field and ionization created. A new lightning model has been employed; i.e., we have included a horizontal channel in addition to the conventional vertical channel. The effects of the horizontal lightning channel are summarized as follows: (1) the effect of a vertical channel plays a fundamental role in the whole view of sprite initiation; (2) the position of a sprite is shifted from the position of its parent vertical channel in response to the length of a horizontal channel; and (3) we observe very fine structures with local maxima and minima in the “reduced” electric field (the electric field divided by the neutral gas density). These theoretical inferences are discussed and compared with the observational facts so far reported (such as lateral shift of sprites, morphological difference of sprites, etc.).  相似文献   

On the fine structure of the ground-based vlf chorus as an indicator of the wave-particle interaction processes in the magnetospheric plasma     

S.S. Sazhin  M. Hayakawa  Y. Tanaka 《Planetary and Space Science》1985,33(4):385-386

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The correlation of whistler occurrence rate at a low latitude with thunderstorm activity at its conjugate region and with solar activity   总被引：1，自引：0，他引：1  

Kenji Ohta  Masashi Hayakawa 《Pure and Applied Geophysics》1990,133(1):167-178

The correlations of occurrence rate of whistlers in January during one solar cycle (1977–1987) at a low latitude station (Yamaoka, geomag. lat. 25°, L=1.26) with thunderstorm activity near its conjugate region and also with solar activity have been investigated, and it is found that the occurrence rate has no correlation with the lightning flashes near the conjugate point, while it is negatively correlated with solar activity. On the basis of these findings it is suggested that the ionospheric absorption is of major importance in the long-term variation of whistler occurrence rate, with the duct formation being of secondary effect, while the lightning activity is only a necessary condition for whistler occurrence.  相似文献   

A cross-correlation analysis of tidal current,water temperature and salinity records     

Hideo Nakajima  Norio Hayakawa 《Journal of Oceanography》1982,38(2):52-56

Fifteen day records of current velocity, water temperature and salinity were obtained at a coastal station in the Seto Inland Sea. It was observed that water movement was characterized by an exchange of two distinctive water masses east and west of the station. Cross-correlation analysis shows that, at the semi-diurnal period, the motion of these characteristic waters causes temperature and salinity variations. At frequencies higher than 2 cycles per day where power spectra of current velocity have a slope of ?5/3, coherence between current velocity and both water temperature and salinity decreases rapidly.  相似文献   

Anomalous heat flow in Japan     

M. Hayakawa 《Bulletin of Volcanology》1969,33(1):57-67

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Geophysical study of matsukawa geothermal area,iwate prefecture,Japan     

M. Hayakawa 《Bulletin of Volcanology》1966,29(1):499-516

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Gradients and phase velocities of ULF geomagnetic disturbances used to determine the source of an impending strong earthquake     

V. S. Ismaguilov  Yu. A. Kopytenko  K. Hattori  M. Hayakawa 《Geomagnetism and Aeronomy》2006,46(3):403-410

Results of studying the behavior of the vectors of gradients and phase velocities of ULF geomagnetic disturbances (F < 1 Hz) in the Japan seismic zone are presented. The gradient and phase velocity vectors along the Earth’s surface were determined using data of the group of three high-sensitivity three-component magnetovariation stations (MVC-3DS) located at triangle vertices at a small (～5 km) distance from one another (magnetic gradiometer). Two such groups of stations were installed in 1999 southwest and southeast of Tokyo at a distance of ～150 km from each other. It has been indicated that, several months before strong earthquakes (M > 5), the values of gradients and phase velocities start anomalously changing, and directions toward sources of impending strong earthquakes appear in the distribution of gradient vector directions. Directions from sources of impending earthquakes appear in the distribution of phase velocity vector directions. It is proposed to use gradients and phase velocities of ULF and ELF geomagnetic disturbances as one of the factors in a short-term prediction of strong earthquakes.  相似文献