臺灣博碩士論文加值系統

本論文修改Wernik所提出建構訊號閃爍分布之方法獲得以華衛一號衛星所量得電離層的離子密度為基礎的赤道區不同季節變化的訊號閃爍分布模式。此獲得訊號閃爍模式的方法以最佳化可靠區原理為基礎，對所獲得離子密度頻譜進行最小平方差曲線比對，以獲得頻譜參數：頻譜斜率及最大尺度。在弱閃爍條件下(S4<0.3)，我們獲得的S4分布與過去文獻發表的結果相近。然而當閃爍程度加強(0.3< S4<0.6)，S4在緯度上的分布則移至赤道異常區。此外本論文所獲得的最大尺度分布對於研究不規則體的演化具有頗大助益。我們進而討論訊號閃爍分布隨不同參數的改變，其中影響的參數包含地磁緯度、地球經度、本地時間、太陽活動及地球磁場變化。
除此之外我們以一組特殊量測資料作詳細電波通過電子不規體而產生閃爍現象的研究。此資料為在西元兩千年三月二十四日晚間同時獲得Ascension Island地面閃爍訊號及ROCSAT-1衛星量測到太空不規則體離子密度資料。首先我們對地面閃爍訊號進行統計分析，其結果顯示Nakagami分布可以用來描述S4大到1.4的L-Band閃爍訊號。其次由於多重反射的效應，在弱閃爍條件下所預測S4與頻率的相關趨勢也不成立，對地面閃爍訊號進行頻域及時域分析發現VHF訊號比L-Band訊號承受較嚴重多重反射效應的影響。進而我們對所量測到的離子濃度及地面閃爍訊號加以比對並研究兩者變化的關係。結果離子濃度與閃爍訊號的因果關係在部分資料內可觀察到。最後以PEM數值模擬方式執行閃爍訊號數值模擬和Ascension Island量測資料進行比對，藉以驗證此同時量測到太空及地面量測資料的事件確實發生。

The global/seasonal/local-time distributions of scintillation occurrence rate have been obtained from the in-situ density measurement of ROCSAT-1 during moderate to high solar activity periods of 2000 to 2003. The scintillation was obtained with a modified procedure of the thin-phase screen model of Rino reported in Wernik et al. [2007]. The distribution of the S4 index for the weak scintillation (S4<0.3) is almost identical to that of the equatorial irregularity distribution reported in the literature. However, as the scintillation level increases (0.3< S4<0.6), the latitudinal distribution moves to the equatorial ionization anomaly (EIA) region. In addition, the distributions of the outer scale values that are valuable for the study of physical evolution of the irregularity structure are also obtained. The occurrence distribution of scintillation activity with several parameters such as dip-latitude, longitude, local time, solar activity, and geomagnetic activity during different seasons are presented and discussed in the report. In addition, a special case of coincident observation that occurred on 24 March 2000 between the irregularity structure measured by ROCSAT-1 and the scintillation experiment at the Ascension Island has been studied. The study of scintillation statistics is carried out first and the results shows that the Nakagami distribution can portray the scintillation intensities with S4 up to 1.4 for the L-band scintillation. Moreover, the departure of frequency dependence of S4 predicted by the weak scintillation is noticed due to the multiple scattering effect. The measurements between the satellite and scintillation data are then compared against each other to study the similarity in the gross feature between the characteristics of irregularity structure and the scintillation variation. The causal relationship between the fluctuation of ion density and the scintillation variation is obtained. The coincident observations are also validated by the PEM simulation result.

Table of Content i
List of Figures ii
Chapter 1 Introduction 1
1.1 Introduction to the Motive of Study 1
1.2 Introduction of ROCSAT-1 7
Chapter 2 Irregularity Density in the Equatorial Region 11
2.1 Driver of the Irregularity in the Equatorial Region 11
2.2 The linear theory of the Rayleigh-Taylor Instability 13
Chapter 3 The Scintillation Theory 19
3.1 Thin Phase Screen Theory 19
3.2 Parabolic Equation 25
Chapter 4 ROCSAT-1 in-situ data and data processing 28
4.1. Data Processing 28
4.2 Results and Discussion 31
4.3. Summary 40
Chapter 5 Study of a Coincident Observation 52
5.1 Observations 52
5.2 Results and Discussion 59
5.3 Summary 67
Chapter 6 Conclusion 78
References 83
Appendix A 88
Appendix B 90

Aarons J., Global morphology of ionospheric scintillations, Proc. IEEE. 1982, 70, (4), 1982
Aarons J., The longitudinal morphology of equatorial F-layer irregularities relevant to their occurrence, Space Sci. Res., 63, pp 209-243, 1993
Basu S., Basu S., and Khan B. K., Model of equatorial scintillation from In situ measurements, Radio Sci. 11, (10), pp 821-832, 1976
Basu S., Basu S., High resolution topside in situ data of electron densities and VHF/GHz scintillations in the equatorial region, J. Geophys. Res., 88, (A1), pp 403-415, 1983
Basu S., Basu S., Equatorial scintillations : advances since ISEA-6, J. Atmos. and Terr. Phys. Vol. 47, 753-768, 1985
Basu, S., E. M. Mackenzie, S. Basu, E. Costa, P. F. Fougere, H. C. Carlson and H. E. Whitney, 250 MHz/GHz scintillation parameters in the equatorial, polar, and auroral environments, IEEE Journal on Selected Areas in Communication, Vol. SAC-5, No. 2, 1987
Basu S., MacKenzie E., and Basu S., Ionospheric constraints on VHF/UHF communication links during solar maximum and minimum periods, Radio Sci. 23, (3), pp 363-378, 1988
Basu S., Basu S., Ionospheric structure and scintillation, in Wave Propagation in Random Media (Scintillation), edited by V. I. Tatarskii el al., pp 139-155, Spie Press, Bellingham Washington, 1992
Basu S., K. M. Groves, Su. Basu, P. J. Sultan, Specification and forecasting of scintillations in communication/navigation links: current status and future plans, J. Atmos. Terres. Phys., Vol 64, pp 1745–1754, 2002
Bhattacharyya A., Yeh K. C. and Franke S. J., Deducing turbulence parameters from transionospheric scintillation measurements, Space Sci. Rev., 61, pp 335-386, 1992
Cervera M.A., Thomas R. M., Groves K. M., Ramli A. G., and Effendy, ‘Validation of WBMOD in the Southeast Asian region’, Radio Sci. 36, (6), pp 1559-1572, 2001
Franke, S. J. and C. H. Liu, Observations and modeling of multi-frequency VHF and GHz scintillations in the equatorial region, J. Geophys. Res., (88), A9, pp 7075-7085, 1983
Fremouw, E. J., R. C. Livingston and Deborah A. Miller, On the statistics of scintillating signals, J. Atmos. Terres. Phys., Vol 42, pp 717-731,1980
Kelley, M. C., The earth's ionosphere: plasma physics and electrodynamics, Academic Press, 1989
Kil H., Heelis R. A., Equatorial density irregularity structures at intermediate scales and their temporal evolution, J. Geophys. Res., 103, (3), pp 3969-3981, 1998
Li Sheng-Yi and Liu C. H., Modeling the effects of ionospheric scintillation on LEO satellite communication, IEEE Commun. Lett., 8,(3), pp 147-149, 2004
Liu, Y. H., C. H. Liu and S.Y. Su (2012), Global and Seasonal Scintillation Morphology in the Equatorial Region Derived from ROCSAT-1 In-situ Data, Terr. Atmos. Ocean. Sci., Vol 23, No. 1, pp 95-106, doi: 10.3319/TAO.2011.06.30.01(AA).
Liu, Y.H., C.K.Chao, S.Y.Su and C.H.Liu (2012), Study of a coincident observation between the ROCSAT-1 density irregularity and Ascension Island scintillation, Radio Sci., Vol. 47, RS5001, doi: 10.1029/2011RS004908
Potter, D., Computational physics, John Wiley & Sons Ltd. 1973
Rino C. L., A power law phase screen model for ionospheric scintillation 1. weak scintillation, Radio Sci., 14, (6), pp 1135-1145, 1979
Rino, C. L. and C. H. Liu, Intensity scintillation parameters for characterizing transionospheric radio signals, Radio Sci., Vol. 17, (1), pp 279-284, 1982
Rino C. L. and Owen J. , Numerical simulations of intensity scintillation using the power law phase screen model, Radio Sci., 19, (3), 891-908, 1984
Rino, C. L. (1992), On the Statistics of Equatorial Transionospheric Radio Waves, in Wave Propagation in Random Media (Scintillation), edited by V. I. Tatarskii el al., pp 124-138, Spie Press, Bellingham Washington
Rino, C. L. (2011), The theory of scintillation with applications in remote sensing, A John Wiley and Sons, Inc., New Jersey
Secan J. A., Bussey R. M., E. J. Fremouw and Sa Basu, An improved model of equatorial scintillation, Radio Sci., 30, (3), pp 607-617, 1995
Secan J. A., Bussey R. M., E. J. Fremouw and Sa Basu, High-latitude upgrade to the Wideband ionospheric scintillation model, Radio Sci., 32, 1567-1574, 1997
Su S. Y., Liu C. H., Ho H. H., and Chao C. K., Distribution characteristics of topside ionospheric density irregularities: Equatorial versus midlatitude regions, J. Geophys. Res., 11, A06305, doi:10.1029/2005JA011330, 2006
Sultan, P. J., Linear theory and modeling of the Rayleigh-Taylor instability leading to the occurrence of equatorial spread F, J. Geophys. Res. 101, 26, 875-891, 1996
Sun WenYu, Yuan Ya-Xiang, Optimization theory and methods nonlinear programming, Springer, New York, NY, 2006
Tsunoda, R. T., Control of the seasonal and longitudinal occurrence of equatorial scintillation by the longitudinal gradient in integrated E region Pedersen conductivity, J. Geophys. Res. 90, 447-456, 1985
Tylor L. and C.J. Infosino, On the strong phase screen theory of ionospheric scintillations, Radio Sci., 11 No 5,459~463, 1976
Thomas F., Coleman and Yuying Li, An interior Trust Region approach for nonlinear minimization subject to bounds, SIAM J. Optimization , 6, (2), pp 418-445, 1996
Wernik, A. W. and C. H. Liu, Ionospheric irregularities causing scintillation of GHz frequency radio signals, J. Atmos. Terres. Phys., Vol. 36, pp 871-879, 1974
Wernik A. W., Secan J. A., and Fremouw E. J., Ionospheric irregularities and scintillation, Adv. Space Res. 31, (4), pp 971-981, 2003
Wernik A. W., Alfonsi L., and Materassi M., Scintillation modeling using in situ data, Radio Sci. VOL. 42, RS1002, 21 PP., 2007 doi:10.1029/2006RS003512
Wheelon A. D., Electromagnetic Scintillation I, Cambridge University Press, Cambridge, UK, 2003
Wilkins, M. L. (), Computer simulation of dynamic phenomena, Springer, Berlin, 1999
Yeh K. C., Liu C. H., Diagnosis of the turbulent state of ionospheric plasma by propagation methods, Radio Sci. 12, (6), pp 1031-1034, 1977
Yeh K. C., Liu C. H., Radio wave scintillations in the ionosphere, Proc. IEEE, , 70, (4), pp 324-360 1982