Mode Conversion Processes from Electrostatic Plasma Waves into Electromagnetiic Waves in the Space Plasma

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The mode conversion process from electrostatic plasma waves into electromagnetic waves is one of the main processes to produce electromagnetic radiations in the space plasma. In the present study, we have investugated the mode conversion proceses taking place in the terrestrial hectomrtric radiations (THRs), auroral kilometric radiations (AKRs)and Jovian decametric radiations (DAMs) by using the data of plasma wave detector (PWS) onboard the Akebono satellite as well as the data obtained by the ground based observations. As for the THRs, we have found that strong componets of THRs are generated at the fixed frequencies of 1.7MHz and 3.4MHz ; these waves are generated by the condition that the UHR frequency of the source becomes the twice of the local electron cyclotron frequency. For the intense R-X mode AKRs, it has been found that the Doppler conversion process is one of the important processes, and the cyclotron maser process is not the unique generation mechanism of AKRs. Further for the generation mechanism of the Jovian S-bursts, it has been clarified that the occurrence of S-bursts can not be explained by the gometrical effect between the source region and the observer, but it rather indicates the formation of the acceleration region of electron beam at the moment along the magnetic field line which is connected to the satellite Io.