MULTI-STATION SYSTEM FOR SOLAR-WIND OBSERVATIONS USING THE INTERPLANETARY SCINTILLATION METHOD

We describe a multi-station system dedicated to measurements of the so lar wind plasma using the interplanetary scintillation technique. The observation system, which is operated at a frequency of 327 MHz, consi sts of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. Th e newest station was constructed at Kiso in 1993 to make a four-statio n system. The present system, however, has insufficient sensitivity to measure enough IFS sources for observing the solar wind with good spa tial and temporal resolution. As a result, for example, one synoptic m ap of solar wind speeds requires the superposition of data for three s olar rotations. Therefore we have begun the project to upgrade the ant enna system at each station. To start with, the Fuji antenna has succe ssfully been improved with an optimum design of the primary feed syste m and the development of a low noise preamplifier. The Fuji antenna sy stem after the improvement achieved the minimum detectable flux densit y of 0.3 Jy (bandwidth: 10 MHz, time constant: 100 ms) which is nearly five times better than the previous system. This upgrade project is e xpected to be fruitful during the coming decade for solar wind study.