Yoshio Takeya

Graphical analysis method for a retarding potential analyzer and its application to the real-time measurements of ion temperature in space plasmas

In order to obtain the ion temperature from a voltage‐to‐current characteristic of a retarding potential analyzer (RPA) in a drifted density (106 1/cc), low‐temperature (1 eV) plasma such as an ionospheric plasma, optimum fitting procedures using the digital computer have been used. But these methods must take a lot of time to search the parameters. A graphical method using the sampling of a RPA curve has been developed to obtain the ion temperature quickly. Many diagrams were drawn by calculation to determine the ion temperature. This method is suitable not only for the processing of a large quantity of data but also for the in‐flight data analysis aboard a sounding rocket. By the use of feedback control circuits, ion temperature data could be obtained at a ratio of several tens per second in the ionosphere, where the mass of the ion M varies slowly. The accuracy of this method and the effect of variations of M, angle of attack Θa, and drift velocity v0 is discussed. Also the efficacy of this method is c...

Plasma injection into a simulated magnetosphere

Abstract In an attempt to study the behavior of magnetospheric plasma, a laboratory “lerrella” experiment was performed using a plasma emitter which was a newly designed small discharge tracer called Powered Double Probe (PDP). The tracer plasma was observed optically along the magnetic field line which crosses the PDP position. The configuration of the magnetic field lines which are deformed by the plasma kinetic energy is one of the most important features of such a system. This paper deals with the usefulness of the PDP and an experimental study of this plasma injection into the simulated magnetosphere in the absence of the interplanetary magnetic field (IMF). By discharging the PDP a luminous plasma was observed along the magnetic field lines of a pure dipole field (without plasma flow) and a distorted dipole field (simulated magnetosphere) like a flash bulb converting a time exposure camera into a time resolved camera. From these observations it is deduced that a deformation of magnetic field line at the nightside region, in a sense of a decreasing magnetic field, is a result of interaction between a plasma flow and a dipole field, but no neutral sheet region exists in the simulated magnetosphere in the range of 30 earth radii for zero IMF. Also no notable oscillation or instability of the magnetic field lines in the simulated magnetosphere were observed. This supports the possible existence of “ground state” of the actual magnetosphere which was defined by a theoretical study of substorm mechanism.

Radio-radar and optical observations of cesium releases in the upper atmosphere

Abstract A series of rocket experiments in which cesium ionized clouds were artificially produced by evening twilight chemical releases in the upper atmosphere has been conducted at Kagoshima Space Center, University of Tokyo. In these rocket series, simultaneous radio-radar and optical behaviors of artificial cesium clouds have been successfully investigated. This study indicates the utility of combined radio-radar and optical observations and presents the results to estimate the chemical yield, diffusion features in the magnetic fields and drift motions due to the ionospheric winds.