Chapter.3 Ionosphere

1. Chapter.3 Ionosphere Speaker :吳孟哲 Group 3 吳孟哲 任維崧 謝岳均 林伯勳

2. Introduction • Upper atmosphere About Classification of the atmosphere: neutral temperature: troposphere, stratosphere, mesosphere, thermosphere composition Ratio: homosphere, heliosphere processes : turbosphere, diffusosphere(> 500-700 km, exosphere) electron density :E, F layer (region) • High Frequency radio wave are reflected due to high electron plasma frequencies.

3. 100 公里高度由國際航空聯盟定義為太空的邊緣界線（卡門線）。高層大氣的範圍不但包含卡門線，也直接包含有超過700顆人造衛星運作的低軌道(Low Earth Orbit，簡稱 LEO)。 http://www.ss.ncu.edu.tw/~uadl/Research.htmlNCU Upper Air Dynamics Laboratory https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line

4. The structure and Dynamics of the thermosphericNeutral Atmosphere • Formed from plasma. • High density

5. Neutral atmosphere is heating by the absorption radiated by the sun

6. Gravitational Separation and Composition Below 105 km turbulent diffusion dominates

8. Thermospheric winds HWM-93 output for monthly mean zonal wind profiles at Munich, Germany (48.1 • N, 11.6 • E). The changing direction of the stratospheric wind jet from winter to summer leads especially to horizontal variations in the propagation pattern of infrasound. https://www.researchgate.net/figure/HWM-93-output-for-monthly-mean-zonal-wind-profiles-at-Munich-Germany-481-N-116_fig11_225020480

10. 3.2 The Formation of the Ionosphere Production rate Loss rate Transport n:the density of the ith ion species. v:ion velocity P:ion production L:ion loss

11. Ionization of the neutral particles by solar EUV radiation Rearrangement collisions between the primary ions and neutral particles Dissociative recombination of molecular ions and free electrons Production Loss

14. The photochemical Equilibrium of molecular Ions

15. (5)

17. The photochemical equilibrium of O+ Pi-Li=q-ne =0 Tokyo 1200hours

18. Science of Space Environment Chapter 3: The Formation of the Ionosphere 3.2.3~3.2.5 Speaker:任維崧

19. Motion of Charged Particles in the F Region (3.15) (3.16) 3.Lorentz force 4.Collisions with particles of other species 1.Gravitational force 2.Pressure gradient force :Accleration of gravity. , :Ion/electron mass. :Boltzmann constant. ,:Ion/electron temperature. :Neutral particle velocity. :Ion/electron density. :Electric/magnetic field. ,:Ion/electron velocity. ,:Ion/electron collision frequency with neutral gas particles. : : :

20. (3.15) (3.17) (3.16) 1.Electron mass is so much smaller than ion mass, there is no energy exchanged in collisions between electrons and ions. (3.18) 2.With regards to electrons, since , then , so the collision term, being much smaller than electromagnetic force term. 3.We assume a single species composition consisting only of ions (=) and equal temperatures ().

21. Drift We shall now consider the components perpendicular to the magnetic lines of force. We set typical conditions in the F region. We see thatequations, and neglecting the neutral atmospheric wind. (3.17) (3.18)

22. For Ion (3.19) “y” “x” ----------① ----------② Subtitute ③ into② Subtitute②into① ----------④ ----------③

23. For Electron (3.20) “x” Combine③ and ④ ----------⑤ “y” ----------⑥ Combine⑤ and ⑥ (3.21) (3.22)

24. For altitudes above the F region the term of and its higher order terms can be omitted. 0 1 (3.23)

25. Ambipolar Diffusion Due to the differences in the masses of ions and electrons , they tend to separate under gravitational force. This separating action leads to the generation of an electric field in the direction of the magnetic field lines. But since the electrons can move easily in that direction, they quickly attempt to neutralize the electric field, so both electrons and ions diffuse by moving together in this field. Electrons Accelerate Finally moving at the same velocity. Slow down Ions

26. Parallel component to the magnetic field lines ( (3.24)

27. Diffusion Equilibrium At higher altitudes, density of the neutral gas constituents becomes low enough so that cam be ignored, and we assume temperature (T) is the same everywhere. ( Set as differential operator (3.25) (3.26) (3.28) (3.27)

28. If we compare this with the diffusive equilibrium of neutral particle, the effect of ambipolar diffusion makes ion masses appear to be one-half their true mass.

29. The Formation of the Region At high below a given altitude, the chemical processes in the production and loss of ions are dominant, electron densities continue to increase with increasing altitude in accordance with the photochemical equilibrium profile. At high altitudes the electron density distribution pattern falls under the diffusive equilibrium, electron density then decreases with increasing altitude. Due to the diffusion, region appears during the daytime and the nighttime. diffusive equilibrium Electron density maximum, near 300km. photochemical equilibrium

30. The Emergence of the Layer When the peak altitude for ionization rate is below the transition altitude, a new bulge appears in the electron density profile, and thus the layer emerges. The layer is more likely to 1. Appear during daytime in the Summer when the solar zenith angle is small, the peak altitude of ionization is low 2. Appear during solar minimums when ionization rates are low, and the transition altitude becomes higher. Transition altitude Ionization altitude

31. E Region (90~150km) Ion production rates are the summation of the contribution from each wavelength band. In the E region, a daily variation is observed in electron density depending on solar zenith angle. The primary ionized species are and, as the photochemical equilibrium between production and loss is reached, finally become the dominant ions.

32. Sporadic E Layer The sporadic E layer is a thin layer of high density electrons which appears irregularly, and its formation and its morphology differs depending on latitude. Here we discuss mid-latitude type. The E region altitude is characterized by a high ion-neutral collision frequency and the particle moving due to the neutral atmospheric wind. ☉ Cause downward drift Cause upward drift Eastward flowing neutral atmospheric wind. Westward flowing neutral atmospheric wind.

33. Sporadic E Layer When at a given altitude boundary, the neutral atmospheric wind below this boundary is eastward, and above the boundary is westward, ions concentrate at the altitude where the wind directions change. The metallic ions, have small coefficients for recombination reactions, which means that these ions have very long lives. Therefore, sporadic E layer is formed. Westward flowing neutral atmospheric wind. Ions concentration Cause downward drift Eastward flowing neutral atmospheric wind. Cause upward drift

34. Sporadic E Layer Since the sporadic E layer is formed by ions drawn into the thin layer by wind shear, diffusion of the ions following cessation of the neutral atmospheric wind causes the disappearance of the sporadic E layer. Also, a strong electron density gradient drives the various plasma instabilities in the region. The sporadic E layer is thus not a regularly occurring, uniform structure, but often occurs as a small-scale, patchy structure.

35. D Region Solar radiation at the Lyman- (λ=121.6nm) line is the ionization energy source for NO, and production of becomes conspicuous in the 60~90km region. This referred to as the D region. Electron density in the D region depends greatly on Solar zenith angle NO density http://www.phys.nthu.edu.tw/~gplab/file/023%20Atomic%20spectrum%20and%20Planck%20constant/H-atomic%20Spectrum%20&%20Planck%20constant%20(TW).pdf

36. D Region The electron density is higher in the D region during the winter if the solar zenith angle does not differ very much. At the lower stratum below the altitude of 80km, a complicated reaction process produces hydrated (or water cluster) ions such as and from ionized species such as and . The dissociative recombination of and electrons occurs at a rate of about 10-times faster than the the/electron recombination, so in the regions where the hydrated ion dominates, electron densities drop rapidly.

37. A Reference Ionospheric Structure International Reference Ionosphere (IRI) COSPAR、URSIformedaworkinggroupto produce empirical standard model of the ionosphere, based on all available data sources. Committee on Space Research (COSPAR) International Reference Ionosphere (IRI) International Union of Radio Science (URSI) PARAMETERS: Electron density electron temperature ion drift ion composition (O+, H+, He+, NO+, O+2) ion temperature ionosphericelectron content (TEC) https://iri.gsfc.nasa.gov/

38. A Reference Ionospheric Structure Electron density is highest, is the major ion species. The transition altitude is higher during the day than at night, so the layer with its dominant molecular ion population appears in the daytime ionosphere. Solar maximum during daytime (1200 hours, LT) and for nighttime (0000 hours,LT).

39. 3.3Variations in the Ionosphere 大氣4B 謝岳均

40. 3.3.1 Geographical Distribution (shown by maps) 3.3.2 Periodically Repeated Variations (shown by timing diagram)

41. The most imortant parameter to describe ionosphere • Major characteristics of the ionosphere. Reflect radio signals in the shortwave band. • Critical frequency(fc)/Penetration frequency. A radio signal whose frequency exceeds plasma frequency at the point of maximum electron density will therefore penetrate the ionosphere.

42. (3.24)p.90 The relation between maximum electron density and foF2 #MKS system of units

43. 3.3.1 Geographical Distribution

44. UT4A.M. 1200noon

45. Equatorial Anomaly The structure composed of two separate rigions with high f0F2 values straddling the magnetic equator is called Equatorial Anomaly. Caused by the combined effects of the upward ExB drift and the subsequent downward diffusion. foF2 reaches its maximum in the vicinity of magnetic latitude 10°~15°. Compare Fig 3.11 and Fig 3.12 can see that the two undulating belt align these lines.

49. Ionospheric Dynamo • Polarization electric field υin>Ωi while υen>Ωe • Conductivity in the direction of the magnetic lines of the force is extremely high in the ionosphere, so the polarization electric field developed at the altitude of the E region is mapped along the magnetic lines of force onto the F region through the magnetosphere.

50. The Magnatic Field Model • Both geomagnetic axis and Earth’s rotational axis having different centers. • The following potential expressed by the expansion of spherical harmonic functions is the mathematical model usually used to express the geomagnetism parameters. r ϵ the distance from Earth’s center gmn,hmn ϵ coefficients determined based on observation data at each specific location