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The Variability of the Martian Thermosphere-Ionosphere

The Variability of the Martian Thermosphere-Ionosphere. Stephen W. Bougher Jared M. Bell (U. of Michigan). Jim Murphy (NMSU). Martian Atmospheric Regions and Processes. Recent Mars Thermosphere-Ionosphere Datasets (Solar Cycle, Inter-annual, Seasonal, Diurnal).

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The Variability of the Martian Thermosphere-Ionosphere

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  1. The Variability of the Martian Thermosphere-Ionosphere Stephen W. Bougher Jared M. Bell (U. of Michigan) Jim Murphy (NMSU)

  2. Martian Atmospheric Regions and Processes

  3. Recent Mars Thermosphere-Ionosphere Datasets (Solar Cycle, Inter-annual, Seasonal, Diurnal) • MGS and Odyssey Accelerometer AB measurements (densities, T): • Latitudinal density gradients and inferred temperatures (Keating et al., 2002). Diurnal variations over ~100-170 km (Withers et al; 2003). • Winter polar warming (100-130 km) driven by inter-hemispheric circulation near solstices (Keating et al;, 2003; Bougher et al., 2005). • MGS longitude variations as a function of season, latitude, SLT, and height in the thermosphere (Forbes et al., 2002; Withers et al., 2003). • MGS/ER derived neutral densities from 170-240 km. • Latitudinal density gradients on the nightside near crustal magnetic field features (Lillis et al., 2005); seasonal variations observed. • MGS/RS electron density profiles (~100-200 km) at SZA >75º: • High N. latitudes (LAT> 65N; SLT ~ 3); • High S. latitudes (LAT> 65S; SLT ~ 3); • Longitude variations obs. in F1-peak heights over 2-Martian years (Bougher et al., 2004)..

  4. Solar Cycle and Seasonal Sampling of the Martian Thermosphere

  5. Martian Upper Atmosphere Sampling fromMGS and Odyssey Accelerometers • MGS Accelerometer data over Phase 1 (7-months) and Phase 2 (4.5 months) aerobraking. Measured densities (inferred scale heights and temperatures) over 110-160 km. Nearly ~1200 vertical structures. • -- Phase 1 : Ls = 180-300; F10.7-cm = 70-90 • -- Phase 2: Ls = 30-95; F10.7-cm = 130-150 • Odyssey Accelerometer data over 5-months of aerobraking. Measured densities (inferred scale heights and temperatures) over 95-170 km. Nearly ~600 vertical structures . • -- Total : Ls = 265-310; F10.7-cm = 175 • -- Following summer 2001 dust storm season

  6. Accelerometer Densities : BLK = MGS1 BLU = ODY (D) GRY = ODY(N) RED = MGS2 (D) GRN = MGS2 (N)

  7. Accelerometer Temperatures :

  8. Schematic of Likely MarsWinter Polar Warming Process Subsidence Adiabatic Heating N Meridional Flow From Summer H. To Winter H. Winter Summer S

  9. Solar Cycle and Seasonal Variation of Exospheric Temperatures (No Coupling)

  10. Longitudinal Variability of Thermosphere from MGS-ACC Data (Outbound: 10-20ºN)

  11. Longitudinal Variability of Thermosphere from MGS-ACC Data (Normalized Wave Amplitudes at 130 km)

  12. Longitudinal Variability of Ionosphere from MGS-RS Data: Height of Primary Electron Density Peak

  13. Mars Upper Atmosphere Modeling Teams • MGCM-MTGCM (Bougher et al., 01; 04; 05): • Coupled/separate models spanning 0-300 km • NCAR (TGCM) and NASA Ames (MGCM) heritage. • Benchmark (validation) for “whole atmosphere” models. • LMD-GCM (Angelat-i-Coll et al; 05; Gonzalez-Galindo et al., 05; ) • Ground to exosphere code (0-240 km) • LMD/AOPP MGCM heritage; LMD/IAA teaming. • ASPEN (Crowley et al. 04; 05) • Troposphere to thermosphere (14-300 km) • NCAR TIEGCM heritage • MM3 (Moudden et al., 04; 05) • Ground to thermosphere code (0-160 km) • Canadian MET model heritage.

  14. MTGCM Input Parameters, Fields, and Domain • Domain : ~70-300 km; 33-levels; 5x5 ° resolution • Major Fields and Species : T, U, V, W, CO2, CO, O, N2 • Minor Species : O2, He, Ar, NO, N(4S) • Ions (PCE) : CO2+, O2+, O+, NO+, CO+, N2+ (<180 km) • Time step : 150 sec • Homopause Kzz = 1-2x 107 cm2/sec (at ~125 km) • Prescribed Heating efficiencies : EUV and FUV (~22%) • Fast NLTE 15-µm cooling and IR heating formulations from Spanish 1-D NLTE code (Miguel Lopez-Valverde) • Simplified ion-neutral chemistry (Fox and Sung, 2001) • Empirical Ti and Te from Viking.

  15. MGCM-MTGCM Simulations: Formulation, Parameters and Inputs: • Separate but coupled NASA Ames MGCM (0-90 km) and NCAR/Michigan MTGCM (70-300 km) codes, linked across an interface at 1.32-microbars on 5x5º grid. Detailed coupling at every grid point and time-step. • Fields passed upward at interface (T, U, V, Z) on 2-min time-step intervals. No downward coupling enabled. • MGCM-MTGCM captures upward propagating migrating and non-migrating tidal oscillations, as well as in-situ driven solar EUV-UV migrating tides in the thermosphere. • Seasonal Simulations: • --Odyssey: Ls = 270; F10.7 = 175; τ ~ 1.0 (TES-YR2) • -- MGS2 : Ls = 90 ; F10.7 = 130; τ ~ 0.4 (TES-YR1) • Conrath parameter scheme used to specify vertical dust distributions (mixed moderately to ~40-50 km). Highly sensitive to vertical dust (Bell et al. 2004).

  16. Seasonal Variability • Mars thermosphere-ionosphere variations throughout the Mars year are driven by: • Seasonal changes in lower atmosphere dust distributions (both horizontal and vertical); • Seasonal changes in migrating and non-migrating tidal propagation from <100 km; • Solar insolation changes owing to Mars eccentricity (aphelion to perihelion).

  17. TES Dust Distributions (Ls = 90): MGS2Year #1 (1999-2000) LAT LON

  18. TES Dust Distributions (Ls = 270): ODYYear #2 (2001-2002) LAT LON

  19. MTGCM Aphelion Case (Ls = 90):Temperatures (K) at SLT=15 (MGS2)

  20. MTGCM Aphelion Case (Ls = 90): Temperatures (K) at SLT=3 (MGS2)

  21. MTGCM Aphelion Case (Ls = 90): Meridional Winds (m/sec) at SLT=3 (MGS2)

  22. MTGCM Aphelion Case (Ls = 90): Vertical Winds (m/sec) at SLT=3 (MGS2)

  23. MTGCM Aphelion Case (Ls = 90): MGS2Dynamical Heating (K/day) : SLT = 3

  24. MTGCM Odyssey Case (Ls = 270):SLT=17 Temperatures versus Latitude

  25. MTGCM Odyssey Case (Ls = 270):SLT=3 Temperatures versus Latitude

  26. MTGCM Aphelion Case (Ls = 270): Meridional Winds (m/sec) at SLT=3 (ODY)

  27. MTGCM Aphelion Case (Ls = 270): Vertical Winds (m/sec) at SLT=3 (ODY)

  28. MTGCM Odyssey Case (Ls = 270): Dynamical Heating (K/day) : SLT = 3

  29. Ls = 90 (top) and Ls = 270 (bottom) : Densities (kg/km3) and Temperatures (K) at 120 km.

  30. Solar Cycle Variability • Mars thermospheric-ionosphere variations over the solar cycle are driven by: • Solar cycle changes in EUV-UV fluxes; both E10.7 and (F10.7+F10.7A)/2. indices are presently used by aeronomers; • Mars eccentricity changes in solar fluxes must be deconvolved for true solar cycle variability to be quantified; • Solar rotation variations (27-day) must be shifted to Mars solar longitude.

  31. T+(U,V) near Exobase:Ls = 270; F10.7 = 200

  32. T+(U,V) near Exobase:Ls = 270; F10.7 = 70

  33. T+(U,V) near Exobase:Ls = 90; F10.7 = 200

  34. T+(U,V) near Exobase:Ls = 90; F10.7 = 70

  35. Solar Cycle and Seasonal Variation of Exospheric Temperatures (Coupling On) MAX MOD MIN

  36. Electron Density at SLT = 15 and 3 :Ls = 270; F10.7 = 200 SLT = 15 SLT = 3

  37. Electron Density at SLT = 15 and 3 :Ls = 270; F10.7 = 70 LST = 15 SLT = 3

  38. Electron Density at SLT = 15 and 3 :Ls = 90; F10.7 = 200 SLT = 15 SLT = 3

  39. Electron Density at SLT = 15 and 3 :Ls = 90; F10.7 = 70 SLT = 15 SLT = 3

  40. Longitudinal Variability • Mars thermospheric-ionosphere variations as a function of longitude are driven by: • Upward propagating migrating and non-migrating tides, whose magnitudes/phasing vary with LAT & season (Forbes et al., 02; Withers et al, 03); • Neutral density variations drive corresponding PCE ionosphere variations near the primary ionospheric peak (Bougher et al. 01; 04); • Aphelion season longitudinal variations observed to repeat over 2-Martian years (Bougher et al., 04)

  41. MGCM-MTGCM Simulation for Ls ~ 90:(a) Lon. Variation of 133 km densities;(b) Lon. Variation of F1-Peak Heights.

  42. MGCM-MTGCM Simulation for Ls ~ 90:Fractional Density Amp. of σ=2, s=(-1) Tide.

  43. Inter-annual Variability • Mars thermospheric-ionosphere variations from Martian year-to-year are driven by: • Near perihelion changes in lower atmos. dust distributions (both horizontal and vertical); aphelion changes are minimal; • Dust induced changes in migrating and non-migrating tidal propagation from <100 km; • Solar cycle changes in EUV-UV fluxes.

  44. % Differences in Temperatures: Ls = 270 vs 90 (LST = 15; TES Year #2 minus TES Year #1) Ls = 90 Ls = 270

  45. % Differences in Temperature: Ls = 270 (120 km Constant Height)

  46. % Differences in Temperature: Ls = 90 (120 km Constant Height)

  47. Variations in Ionosphere (Ls = 270; SLT = 15): TES Year #1 vs Year #2 TES1 TES2

  48. Conclusions and Summary • Martian long-term thermosphere-ionosphere variability must be considered before SW-ionosphere/thermosphere interactions can be quantified and understood (solar cycle, inter-annual, seasonal, diurnal). • Episodic variations of the Mars thermosphere-ionosphere. Nightside auroral features, episodic neutral thermospheric heating, and ionospheric irregularities are all manifestations of particle (electron) precipitation in cusp regions linked to the crustal magnetic field centers. • Solar cycle plus seasonal orbital variations must be considered together to account for the changes observed in dayside T∞ • Inter-annual variability is significant during perihelion periods, and minor near aphelion (e.g. polar night temperatures and densities; electron density profiles). • Durnal/longitudinal variations are linked to upward propagating migrating and non-migrating tidal oscillations. These tidal effects are strongest during periods when the in-situ solar forcing is weak (e.g. near aphelion, solar minimum conditions).

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