A study of Frozen-in property of 3-m plasma Irregularities in Ionospheric Sporadic E layer

• Main Authors: Chin-Min Tee, 鄭倩敏
• Other Authors: Yen-Hsyang Chu
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/g6998d

碩士 === 國立中央大學 === 太空科學研究所 === 94 === The effects of along and transverse radar beam drifts of sporadic E field-aligned irregularities localized in the expected echoing region on mean Doppler velocity and spectral width are theoretically investigated in this thesis. Detailed analysis shows that the Doppler velocities are nearly linearly proportional to the mean angular distance of the irregularities from the radar beam axis decreases with the increase of the horizontal dimension of the plasma structure. Therefore it suggests that the beam broadening effect caused by the drift of the field-aligned irregularities across the radar beam in the geomagnetically zonal direction may play a role in broadening the Doppler spectral width. Four different algorithms for best fitting plasma irregularity data to theoretical expression are discussed here to obtain the optimal solution of transverse beam drift velocity. In order to facilitate mathematical manipulation, the comparison between estimated radial velocity and observed Doppler velocity is made and correlation analysis is also discussed in the articles. In a special case, however, the correlated coefficient between observed Doppler velocity and estimated radial velocity can be as large as 0.8 or more; and the Root-mean-square (RMS) error is in the range of 1 – 3 (m/s). We find that the algorithm of the least squares fit in terms of radar spectra at fixed height for long duration will result in the best solution for the estimation of transverse beam drift velocity. It is easy to see that the beam broadening effect caused by the drift of the field-aligned irregularities across the radar beam in the geomagnetically zonal direction do play a role in broadening the Doppler spectral width.