Study of interaction between neutral and ionized atmosphere through field-aligned

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From our previous studies we expect that field-aligned irregularities (FAI) in the ionospheric F- and E-regions are associated with the Perkins instability and the gradient-drift-instability, respectively. However we are still far from the understanding of their complicated generating processes and reason of spatial structures. With this grant-in-aid for scientific research, we conducted number of observation campaigns in Japan and abroad to reveal coupling processes between neutral and ionized atmosphere, and published 40 papers to famous international journals. Following is the list of studies we conducted under this grant.1. We developed a new radar of 31.57 MHz for observing E-region FAI and meteor echoes. We can measure neutral winds simultaneously with the E-region FAI echoes. The radar was completed in the MU radar site in 2000, and used for long-term experiment. We could find accurate frequency occurrence of the FAI echoes, and its correlation with the neutral winds.2. Study of E-region FAI : We operated the FM-CW radar of Communication Research Laboratory in Fukui obtain ionogram simultaneously with the MU radar. In USA radar observations of Quasi-Periodic echoes were conducted with SRI International. We developed two dimensional computer simulation, and studied generation of polarization electric field.3. Study of F-region FAI : We participated in the WestPac campaign (network of ionosondes from Taiwan to Indonesia), and operated the FM-CW radar in Cebu, Philippines. We conducted the FRONT campaign to study F-region ionosphere and FAI with the MU radar, airglow imagers and GPS receivers. With the Equatorial Atmosphere Radar completed in Indonesia, we conducted the first observations of FAI in the southern low-latitude region. Through these observations we studied F-region FAI and its relationship to the background atmosphere.