OBSERVATION OF NEUTRAL WINDS, ELECTRIC FIELDS AND LARGE-SCALE STRUCTURES WITH FAI ECHOES

*L. M. Kagan[1] ,M. Yamamoto [1],S. Fukao [1],P. B. Rao [2]
Radio Science Center for Space and Atmosphere, Kyoto University[1]
National MST radar facility, Tirupati, India[2]

We present a method to study processes inducing the field-aligned irregularities (FAI) which are detected with the MU radar in the ionospheric E region. The method allows reconstruction of driven forces for FAI generation (electric fields, neutral winds and large-scale ionization clouds). The procedure of data processing is based on the strong altitude dependence of collisional frequencies, which determines an altitude resolution of the method. The averaged zonal wind and the larger-irregularities scale may be found when the similar backscatter signals are successively seen by the neighboring MU-radar beams.

We present a method to study processes inducing the field-aligned irregularities (FAI) which are detected with the MU radar in the ionospheric E region. These irregularities affect radio wave propagation and thus, define reliability of radio communication and navigation. The driven forces for FAI generation are electric fields, neutral winds and large-scale ionization clouds (sporadic-E layers and large-scale plasma inhomogeneities in particular). So, to understand physics of backscatter from FAI the data on electric fields, neutral winds and large-scale plasma structure within the range and time of backscatter occurrence are necessary. Those observed with rockets are expensive and rare. We propose the procedure of MU radar data processing to find (1) the range-time distribution of a zonal electric field and a meridional wind (above 110 km altitude a zonal wind also), (2) averaged zonal wind and (3) the typical scale of larger-scale structures during the backscatter events. The suggested method of reconstruction of an electric field and a neutral wind is based on the strong altitude dependence of collisional frequencies. The altitude resolution of the method is determined by the altitude dependence of ionospheric parameters. The averaged zonal wind and the larger-irregularities scale may be found when the similar backscatter signals are successively seen by the neighboring MU-radar beams.