利用雷達干涉法已經證明中壢雷達的電離層回波伴隨著波束加寬效應，這個理 論基於兩個假設：其一為天線輻射波束的場型和不規則體散射回波功率都是高斯分 布的形狀，其二為電離層場列不規則體（FAI）都以等速度通過回波區；理論上觀 測的都卜勒速度、頻寬與FAI 平行、垂直於波束主軸的漂移速度分量、平均偏離波 束主軸的角度、沿東西方向延伸長度及天線波束寬間有一線性的關係，因此由重建 FAI 的三度空間結構可以萃取出FAI 沿東西方向的漂移速度，這個理論已經由中壢 52MHz 的觀測資料得到驗證。本計畫之目的在於延續先前所建立電離層波束加寬 理論，以及利用52 MHz、30 MHz 雷達的個別觀測與聯合觀測，蒐集更多赤道異 常區散塊E 層資料，研究中壢地區散塊E 層不規則體橫過雷達回波區的漂移速度， 用以檢驗頻譜寬σ與漂移速度Vd 根據非線性兩步驟不穩定理論的關係b aVd ， 持續探討及驗證產生散塊E 不規則體回波的機制。本計畫為全程計畫的第三年若 兩套雷達系統都已就緒，將進行52 MHz 與30 MHz 的聯合觀測，根據國際地磁參 考場(IGRF)模型的分析，兩套雷達的共同回波區約有東西方向±10°的範圍，在可預 期的未來將可同時觀測3 米與5 米尺度不規則體，FAI 在52 MHz 的回波主要可區 分為團狀與層狀兩種不同結構，共同觀測將可以更詳細探討兩種結構，以及有機會 驗證Sudan et al. [1973]兩步驟不穩定理論，經由亂流的二維空間兩階段過程來解釋 大尺度主波激發小尺度擾動體產生的機制。
With the interferometry technique implemented at the Chung-Li VHF radar, the beam broadening effect is known to involve in the radar returns from ionosphere. Two assumptions are made in this effect, first assume that the antenna beam pattern and the distribution of the backscattered power of the irregularities are both Gaussian, second assume that the drift velocity of the field-aligned irregularities（FAI）in the echoing region is constant. Following the theory that both Doppler velocity and spectrum width are linear relate to the drift velocity component lying on cross the radar beam axis and along the radar beam axis component、 mean zenith angle of the localized FAI in the expected echoing region about the antenna beam axis、the extents of the backscatter and the antenna beam width. Thus, from the reconstruct spatial structure of FAI the information of zonal drift velocity can be extracted and has been examined by Chung-Li 52MHz radar. The aim of this proposal is to study the zonal drift velocity of FAI to examine the power law relation b aVd between the observed Doppler spectral widthσand the drift velocity Vd of the irregularities in equatorial anomaly crest zone. By using 52 MHz、30MHz radar respectively or campaign observation to collect more sporadic E data from and to explore two-dimensional turbulent cascade mechanisms of the generation Es FAI. The aim of this proposal is the proceeding ionospheric campaign by using 30 and 52 MHz radars. The interferometry technique analyze 3-m FAI have shown there are blob and layer two species FAI spatial structures. Furthermore, there are about ±10°common echo region of these two radars from the estimating of IGRF model. Therefore, from the co-observation of two scales of irregularities can be used to examine the nonlinear turbulence energy cascade process from primary plasma wave associated with the gradient drift instability [Sudan et al.,1973], and much more detail discussion about these two spatial structures of FAI.
