摘要
過去動態式電離層觀測儀，回波方位觀測受到Fresnel scale 的限制，最小只能觀測到幾公里的不規則體尺度 ，無法看到一公里以下小尺度的不規則體變化情形。而在本文，藉由全反射回波時間上的相位變化與空間的關係，建立相位變化的的結構函數（structure function），所謂的結構函數，是指統計上的隨機統計特徵值，其相位均方差(mean square difference)的值。然後我們再利用已知結構函數 與時間間隔的指數關係圖中的斜率（SIB）與波譜指數ν在2.2＜ν＜2.6時，有著SIB=0.936ν-0.97的關係式。來反推不規則體的波譜指數（spectrum index）。藉由不規則體的波譜指數對時間的分佈圖，來推測不規則體小尺度的變化情形。並由得到的數天觀測結果了解下列結論：1.實際觀測所得結果與模擬的結構函數結果相符2.所得觀測尺度之波譜指數ν值分佈均介於2～3之間。

Abstract
The relevant irregularity spatial domain extends from decameter radio wavelengths to the first Fresnel scale, a few kilometers, using Dynasonde to measure .We present , however, a new approach to investigating ionospheric irregularities, using the temporal structure function of totally reflected radio echo phase variations. We obtain a theoretical relation of both the direct and inverse problems. Although long-period phase measurements are practicable and essential to exploring larger irregularity scales, they require observing modes dedicated to multiple fixed-frequency time series, and this undesirably limits the number of altitudes that can be monitored simultaneously. In consequence, we established a structure function by phase variations.The structure function is one of the common statistical characteristics of a random field. Astructure function estimate is defined as the mean square difference of the field values taken at pairs of locations or times. And we use the relationship between the slop of structure function and spectrum index to calculate small-scale irregularity spectrum index.

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