Takumi ABE

We discuss a new method to measure a permittivity of sample material with the rectangular cavity resonator. A merit of this method is that it is unnesessary to cut the material so as to be inserted fit for the cavity size, and therfore experimental error related to the material dimension is avoidable. Theoretical calculation of the cavity resonant frequency, obtained by the FDTD method, is compared to measured one, for several cases of material width and the permittivity. Both freqiencies are in a reasonable agreement each other within an error of a few percents. The present result suggests that this method is very convetional and effective for the permittivity measurement and it also has a possibility for further application of the permittivity estimation which does not require any processing of the material.

We present a possible suggestion of a way to measure a permittivity without cutting a sample material by means of the rectangular cavity resonator. The theoretical discussion on the possibility is made in this paper, based on the time variation and the resonance frequency of electromagnetic field inside cavity which is calculated by the FDTD method. The material permittivity estimated from the resonance frequency has a reasonable agreement with theoretical one within an error of a few percents. The present result suggests a possibility for further application of the permittivity estimation which does not require any processing of the material.

Standing-wave method in a rectangular waveguide is a convenient method for measuring the permittivity of the materials. But it is found the error due to the deformation became large when the test sample is deformated. In this paper, we applied FDTD which is powerful tool for solving waveguide problem to evaluate the error due to the deformation. As the results, we can estimate the error as a function of the deformation of sample.

In this paper,we discuss on an aplication of the range doppler imaging to measurement of a wave absorbing characteristices without using a wave darkroom.For the 300x3OOmm metal plate,the measureable range of higher than 4O〜5OdB has been obtained.The nor mal incident characteristices of both vertical and porizontal polarization are in close agreement with the theoretial values. These results show that this metod can be applicable to the measurement method of absorbing not in the wave darkroom,but in an usual room.

資料形態 : テキストデータ プレーンテキスト

Thermal electrons in the upper ionosphere are being studied by means of the scientific satellite "AKEBONO". The measurements are electron temperature, electron density and the distribution of electrons in the energy range of 0∿5eV. An overview of the experiment is given and preliminary results on the protonosphere and field aligned current region are presented.

Low energy component of protons in the solar wind was found by means of an observation with the spacecraft "SAKIGAKE". This component is always accompanied by a sudden change in the solar wind parameters such as interplanetary shocks. The difference of bulk speed between the low energy component and normal one amounts to about 60-140km/s, and is strongly affected by the configuration of the interplanetary magnetic field. It is shown that this low energy component was produced by the gyromotion of protons, through an acceleration mechanism, e. g., Fermi process. Furthermore, it seems that there are two types of accelerative process, though these mechanisms are unknown.

Numerical simulations of Boltzmann's equation have been carried out in order to investigate the anisotropy of the electron energy distribution in the topside F region ionosphere. The equation contains both electron-electron collisions and electron-ion collisions. The simulations were compared with the observational data obtained with the electron temperature probe on board the Ohzora satellite. The results show that the anisotropy of the electron energy distribution can be generated in the topside F region ionosphere and that the electron energy distribution can differ from the Maxwell distribution, when an electric field or temperature gradient (heat flux) exists in the plasma. The simulations also indicate the dependence of electron density on the anisotropy of the ionospheric electron energy distribution.

We investigate the heliographic latitude-longitude structure of solar wind speed between Sept. 1985 and Jan. 1987 through the analysis of the solar wind data obtained by Sakigake, Suisei, and IMP-8. Until Jan. 1986,both polar regians had a high-speed stream extended across the equatorial region. After Feb. 1986,high-speed streams were rarely seen on the equator and low-speed streams were ranged along the equator, although there remained a slight wavy pattern in the latitude-longitude structure. This wavy pattern has been stable till the end of 1986.

27-day recurrence-associated phenomena of the solar wind (SOW), the plasma wave (PWP), and the interplanetary magnetic field (IMF) were detected by the Sakigake spacecraft. The heliospheric structures, having a neutral (current) sheet of ∿2×10^4km thickness and a "plasmasheet" of ≳7×10^5km thickness, during April, 1985-August, 1986 and September, 1986-July, 1987,were in the excursion and aligned phases, respectively. In the neutral sheet the IMF direction usually reverses in a minute. Using high time-resolution data, the average ion density and temperature in the heliospheric plasma sheet are also found to be ≳60/cc and ∿20×10^4K, respectively.

Periodic components were picked up by applying maximum entropy method to the visual brightness of comet Halley which was measured from the ground. 2.22 days' period appears between November 1985 and February 1986. This period is the same as obtained by using Planet-A and Vega imaging experiments. This rotational period shifts to 2.33 days after April 1986. 7.4 days' period is detected from March to April 1986. Millis and Schleicher also indicate that the rotational period of the comet is near 7.4 days. Between March and May 1986,3.4 days' period appears, which can be explained by assuming that 2.33 days' period is modulated by the period of 7.4 days.

Solar wind parameters measured by SAKIGAKE around the time of encounter with Halley comet are discussed Sakigake was in or near the neutral sheet of Heliomagnetosphere and therefore the solar wind velocily was comparatively slow. Interplanetary space was in a small disturbance period. Although a firm evidence does not exist that solar wind velocity was decelerated by Halley's comet, frequency spectrum analysis of the solar wind parameters shows the exisistence of water group ions.

Electron temperature was measured with planar plobes boarding on ISAS 10th scientific satellite "OHZORA". The simultaneous measurments of electrons moving along geomagnetic line of force with those moving perpendicularly revealed anisotropy of the electron temperature. In the region of geomagnetic latitude above 20 degrees, electron temperature measured with the probe which surface is perpendicular to the geomagnetic line of force, T_⫽ is, in most cases, higher than that measured with the one parallel to geomagnetic field, T_⊥. Below 20 degree, T_⊥ was higher than T_⫽ with some exceptions. A celear local time dependence can be seen; in night time the events that T_⫽ was higher than T_⊥ were more frequently observed than those that T_⫽ was lower than T_⊥. No correlation between temperature anisotropy and Kp index was observed. The anisotropy of electron temperature will interpret some discripancies of electron temperature measured so far.