Active Experiments of Wave-Wave and Wave-Particle Interaction by Using EXOS-D (AKEBONO) Satellite

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Main objectives of this project were to do colaborative expeiments with an ionospheric heating facility HIPAS (High power active stimulation) near Fairbanks, Alaska, which is operated by UCLA, using our satellite Akebono, and another colaborative experiment with the U. S. scientific satellite DE-1.During these two years, we have been able to achieve successful results by the HEPAS experiments, but not able to get fruitful result by the DE-1 project, due to several unexpected situations of the satellites. During the last half year in 1990, we also made colaborative experiments with an ionospheric heating facility near Tromso in Norway.HIPAS is a high power HF radio transmitter (2.85 MHz and 1 MW) to heat the ionosphere. We have modulated the HF radio wave with a VLF frequency. As the result, an ionospheric current of the VLF frequency flows in the heated ionosphere, which radiates a VLF radio wave upwards and downwards. We have tried to observe this VLF radio wave by using our satellite Akebono and a receiver on the ground. In August, 1989, we succeeded to detect the VLF signal associated with HIPAS ionospheric heating on the ground by a VLF receiver 35 km away from the HIPAS. Satellite observations were not successful. We could successfully detect this VLF signal with Akebono at 2,300 km of altitude on November 28, 1989 and at 10,000 km on June 18, 1990 as well as on the ground.In November, 1990, we have made similar colaborative experiments with the Tromso ionospheric heating facility in Norway. The experiment on November 18 was successful for a satellite altitude of 1,200 km. As mentioned above, our joint experiments were satisfactory, in order to clarify the mechanism of VLF wave radiation from the heated ionosphere and the mode of propagation to the space and to the ground.