無線電科學 ～ 越來越紅的老科學～

1. 無線電科學～越來越紅的老科學～ 主講人：劉兆漢

7. The First Hundred Years • 1865-1873 Maxwell Equation,Prediction of the • existence of Radio( EM) Waves • 1888 Hertz experimentally found the radio waves • 1901 Marconi demonstrated Propagation of • Radio Waves across English Channel • 1907 Cross-Atlantic radio wave propagation • experiment, Marconi • 1920-1930 Appleton experimented with the idea of • radar, found Ionosphere

8. 1935-1945 Invention and application of Radar • 1945 Discovery of NMR • 1947 Dawn of Radio Astronomy; • First idea of Cellular Phone • 1948 Invention Transistor • 1955-60 Invention of MASER and LASER • 1957 First Satellite(Sputnik) • 1964 communication and weather satellites

16. 大旱期 1965～1980 • 光纖通訊 • 數位時代

17. 天降甘霖 • 個人通訊 • 行動通訊

18. 新方向 • 通訊 • 遙測 • 生物醫學應用 • 智慧型家用

19. Space Weather : Science and Application

20. 太陽黑子

21. Magnetic storms Fig2.2

22. Reconnection Fig2.3

23. ACTIVITY EFFECTS in GEOSPACE • Electromagnetic Radiation: Flare X-rays and UV affect ionosphere/communications. • Energetic particles form shock wave, move magnetosphere, enhance radiation belts, and cause geomagnetic storms & substorms. • Geomagnetic storm current systems preceed elevated high energy electrons. • Auroral Substorm current systems and fields affect satellites directly.

24. EFFECTS on SATELLITES • Magnetopause Crossing Events (MPEs) - shock wave compresses magnetosphere inside satellite orbit altitude (5.6 Re) near noon and on flanks of magnetotail. Causes magnetically oriented satellites to lose Earth pointing.

25. EFFECTS on SATELLITES • Navigation Satellites in outer trapping region (half-geostationary altitude) encounter fields & currents during substorms and magnetic storms - lose frequency/time standard.

26. EFFECTS on Surface Technology • Radio communications eliminated or over amplified depending on frequency. • HF-DF systems disoriented. • Geodetic surveys interrupted. • Ship navigation disrupted. • Power system failures from induction. • Pipeline corrosion & bad chip production

27. Effects on Humans • All ground-based effects are important for impact on humans. • High altitude aircraft radiation effects and all airborne technology effects are impact on humans. • Astronauts directly affected by high energy protons and heavier ions; September and October 1989.

28. Aurora • Auroradisplays Fig1.1

29. Fig1.2

30. Fig1.3

31. Fig1.4

32. 電離層的發現

33. Properties of Radio Waves • Amplitude • Phase • Polarization • Frequency

34. Phenomena Associated with Radio Wave Propagation • Line-of-Sight Propagation • Refraction • Reflection • Diffraction • Scattering • Absorption • Attenuation • Doppler Effect

35. Ground Based Ionosonde • Send radio waves from the ground to the ionosphere. The reflected signal yields information about the bottom-side of the ionosphere such as the electron density and the motion of the charged particles

37. SPUTNIK, 1957

38. Satellite Radio Beacon Experiment • Radio beacon signal is sent from the satellite and received on the ground • From the polarization of the received signal one can deduce the Total Electron Content (TEC) of the ionosphere which is the integrated electron density in the ionosphere along the ray tube of the radio wave from the satellite to the ground

40. EquatorialBubble

43. Scintillation • Plasma instabilities • Ionosphere density irregularities • Scattering of radio waves • Scintillation

45. QP diffraction pattern at the beginning of an intense scintillation patch (West Wall)

46. Correlation Analysis insmallscale D=216m dt=1.62s D/dt=133m/s

49. Computerized Ionospheric Tomography • J.R.Austen, S.J.Franke and C.H.Liu, 1988, • Radio Sci. V.23, 299-307. • The idea of ionospheric tomography was first proposed and proven. • Opened the new field of CIT • Affordable. Robust technique for ionospheric probing