1. High Altitude Observatory (HAO) – National Center for Atmospheric Research (NCAR) The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation. An Equal Opportunity/Affirmative Action Employer. Earth’s Atmosphere with focus on the upper atmosphere – above 100km (Thermosphere and Ionosphere) Gang Lu High Latitude Observatory National Center for Atmospheric Research 2007 Summer School for REU

2. Outline Atmospheric Layers The Thermosphere & Ionosphere Electrodynamical Processes in the Ionosphere Storm Impacts on the Upper Atmosphere Homework Problems

3. Atmosphere Layers

4. The Thermosphere

5. Pressure gradient: For perfect gas approximation: Combining the above 2 equations yields: is the scale height Atmospheric Distribution under Hydrostatic Equilibrium z is altitude g(z) is the acceleration of gravity  is mass density k = Boltzmann’s constant M = mean mass of the molecules If H does not vary with altitude z:

6. Atmospheric Density Distribution If T, M, and g are not functions of z: Diffusively separating atmosphere (above ~100 km): m i is the molecular weight of individual species Mixed atmosphere (below ~100 km): M is the mean molecular weight of atmospheric gases Each species has its own scale height.

7. Column Density: the number of molecules per unit area in a column above z 0 : If H is independent of altitude: Column Density Total Electron Content: 1 TEC Unit = 10 12 electron/cm 2

8. Ionospheric Regions

9. Solar Min and Max Distributions

10. Ionospheric Regions Day and Night Distributions

11. Sources of Ionization Galactic Cosmic Rays Solar EUV and X-rays Courtesy of Scot Elkington

12. Altitude Attenuation of Solar Irradiance Thermosphere Mesosphere Troposphere Stratosphere

13. Ionization Rate (cm -3 sec -1 ) Solar MinimumSolar Maximum Courtesy of Stan Solomon

14. Principal Chemical Processes in the Thermosphere and Ionosphere Photoionization: h  + O  O + + e - h  + O 2  O 2 + + e - h  + N 2  N 2 + + e - Collisional Ionization: e - + O  O + + 2e - Dissociative Recombination: O 2 + + e -  O + O N 2 + + e -  N + N NO + + e -  N + O Charge Exchange : H + O +  H + + O O 2 + O +  O 2 + + O N 2 + O +  N 2 + + O Radiative Recombination: O + + e -  h  + O Recombination: O + O + N 2  O 2 + N 2 Conversion: N 2 + + O  NO + + O N 2 + O +  NO + + O

15. Thermospheric Compositions

16. Ionospheric Compositions

17. Electrodynamic Processes In the Ionospere

18. Ionospheric Currents Horizontal Current: Pedersen Current Hall Current where  P = height integrated Pedersen conductivity  H = height integrated Hall conductivity

19. Horizontal Current: Field-aligned Current: JPJP JHJH Region 1 currents Region 2 currents Ionospheric Currents

20. Distributions of Ionospheric Currents

21. Energy Transfer to the Ionosphere Poynting’s Theorem: where For static conditions, the Poynting’s theorem reduces to: magnetic energy mechanical or thermal energy mechanical energy magnetic energy

22. Horizontal Current: Energy Transfer to the Ionosphere Electromagnetic Energy Dissipation: Joule heating (Ohm’s Law) When neutral wind is neglected: When neutral wind is included: plasma drift velocity neutral wind velocity

23. Comparison of Energy Inputs From the Sun to the Earth SourceEnergy Input (W/m 2 ) Deposition Altitude (km) Solar Radiation Total irradiance UV 200-300nm UV 120-200nm EUV 1368 16 0.1 0.003 Surface 0-50 km 50-120 km 100-500 km Particles Solar Energetic Protons Magnetosph. Protons Magnetosph. Electrons Galactic Cosmic Rays 0.002 0.001-0.006 0.003-0.03 0.000007 30-90 km 100-130 km 70-130 km 0-90 km Joule Heating E = 1~100 mV/m 0.000014~0.14100-500 km Solar wind Kinetic 1/2  v 3 Electromagnetic ExB/  0 0.0003 0.00003

24. Solar and Magnetospheric Energy Budget Solar irradiance: 10 17 W (with 0.1% variability) Solar wind kinetic power: 10 13 ~10 14 W Magnetospheric power: 10 11 ~10 13 W  Auroral precipitation: 10 9 ~10 11 W  Joule heating rate: 10 10 ~10 12 W  Ring current injection: 10 10 ~10 12 W  Plasma sheet heating: ~10 11 W  Plasmoid ejections: 10 10 ~10 11 W  Energy input to the magnetosphere: 10 16 ~10 18 Joules  Energy released by a typical CME: 10 24 Joules  Mass input into the magnetosphere: 10 5 ~10 6 kg  Mass released by typical CME: 2~5x10 12 kg Power consumed by US: ~8x10 11 W

25. Solar Flare Effects on the thermosphere and Ionosphere

26. Electron Density at ~110 km During Flare on 9/7/2005 1720UT 1730UT1740UT1750UT 1800UT 1810UT1820UT1830UT 1840UT 1850UT1900UT1910UT 1x10 3 3x10 5 1x10 3 3x10 5 1x10 3 3x10 5 cm-3 Flare onset

27. Neutral Temperature Change at ~350 km During Flare 1720UT 1730UT1740UT1750UT 1800UT 1810UT1820UT1830UT 1850UT 1910UT2000UT2200UT 0 100 oKoK 0 oK oK 0 oKoK Flare onset

28. Solar Energetic Proton Effects on the Upper Atmosphere

29. % Change of Electron Density due to SEPs October 27 – November 5, 2003 Northern Polar Cap Southern Polar Cap

30. Changes of NO X (NO+NO 2 ) and Ozone due to SEPs October 27 – December 31, 2003 O3O3 NO X O3O3 Northern Polar CapSouthern Polar Cap

31. Effects of Magnetospheric Energy Inpout on the Upper Atmosphere

32. TIEGCM Difference TEC Maps During Storm 1600UT 1700UT1730UT1800UT 1830UT1900UT1930UT2000UT 2030UT2100UT2130UT2230UT 8 0 -8 8 0 8 0

33. TIEGCM Difference O/N 2 Ratio During Storm 1600UT 1700UT1730UT1800UT 1830UT1900UT1930UT2000UT 2030UT2100UT2130UT2230UT 0.5 0 -0.5 0.5 0 -0.5 0.5 0 -0.5

34. Neutral Temperature Change at ~350 km During Storm 1610UT 1620UT1630UT1640UT 1710UT 1730UT1750UT1820UT 1900UT 1940UT2100UT2130UT 0 300 Kelven 0 300 Kelven 0 300 Kelven

35. Neutral Temperature Change at ~350km During Flare on Sep. 7 0 100 TN OKTN OK During Storm on Sep. 10 0 300 TN OKTN OK

36. Homework Assignment

37. Homework Problem 1: (a)Name the layers 1 to 4 (b)Identify the curves A, B, C and D

38. Homework Problem 2: If the neutral temperature at 300 km is increases from 1300 o K to 1500 o K during a solar flare event, will the neutral number density at 300 km increase or decrease? Assuming the thermosphere is mainly composed of atomic oxygen.

39. Homework Problem 3: When neutral wind is neglected, Joule heating Q JH is simply expressed as: Rewrite the full expression for Joule heating in the reference frame of neutral wind. Do neutral winds contribute positively or negatively to Joule heating? (Hint: replacing with, where )

40. Dipole Magnetic Field Distorted Magnetic Field

41. Magnetic Reconnection & Circulation x

42. Magnetospheric Topology & Plasma Convection Solar wind Bow Shock Magnetopause Noon-Midnight Meridional Plane Open-Closed Boundary Equatorial Plane Flow lines Dusk Dawn Noon Midnight High-Latitude Ionosphere 60°