Study on ion-wave-plasmas interactions in space plasmas via spacecraft observations and computer experiments-Breakthrough of the magnetospheric physics

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We conducted the fundamental research to make a breakthrough in the study on space plasma physics and magnetospheric physics via spacecraft observations and computer experiments. In spacecraft observations, we always meet the difficulty that we cannot separate the time variation and spatial variation in the observation data. In order to resolve this problem, the simultaneous observations via multiple spacecraft are essential. Since the requirements on weight and size of onboard instruments are very strict in the mission design of multiple spacecraft, we need to miniaturize our instruments. A typical plasma wave receiver system has more analogue parts than other instruments. Therefore, we attempted to realize the analogue parts of a plasma wave receiver system inside a one-chip LSI using the analogue ASIC technology. We design the first stage differential amplifier, low pass filter, and main amplifier with common mode feedback loops, which are stabilize the functions of each amplifier. Since the upper limit frequency of 100kHz is very low, it is impossible to realize the low pass filter using capacitance and inductance inside a analogue ASIC, we designed the gm-C filter, which make use of the conductance of FET inside the ASIC. We also conducted the layout of the connection pattern inside the ASIC chip and submitted the design to the manufacturer. We conducted the function tests and characteristic tests using the manufactured chips. The results will be reflected to the next design. In the computer experiments, we conducted the antenna response in plasmas using the 3-D model. The characteristics of antennas in plasmas as electric field sensors are very complicated. They are strongly depend on the vicinity plasma parameters, plasma sheath, and photo electrons. We established the simulation program for applying to this subject and examined the antenna response using the various plasma conditions.