The Martian Upper Atmosphere Circulation

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The Martian Upper Atmosphere Circulation
Stephen W. Bougher Jared M. Bell (U. of
Michigan)
Darren Baird (UCLA)


Jim Murphy (NMSU)
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Mars Upper Atmosphere Wind Constraints

• MGS and Odyssey accelerometer measurements of
  latitudinal density gradients and inferred
  temperatures (Keating et al., 2002). Winter polar
  warming (100-130 km) driven by inter-hemispheric
  circulation near solstices (Bougher et al.,
  2005).
• MGS Accelerometer extracted cross-track (zonal)
  winds from aerobraking (Baird, 2005).
• MEX NO nightglow observations of SPICAM (Bertaux
  et al., 2005). Nightglow distribution traces
  inter-hemispheric circulation especially during
  solstices.
• MGS/ER derived neutral densities from 170-240 km.
  Latitudinal density gradients on the nightside
  near crustal magnetic field features (Lillis et
  al., 2005).

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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

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Accelerometer Densities
BLK MGS1 BLU ODY (D) GRY ODY(N)
RED MGS2 (D) GRN MGS2 (N)
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Accelerometer Temperatures
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Schematic of Likely MarsWinter Polar Warming
Process
Subsidence Adiabatic Heating
N
Meridional Flow From Summer H. To Winter H.
Winter
Summer
S
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Martian Lower Thermosphere Zonal Winds Derived
from MGS Accelerometer

• Technique (Baird, 2005)
• Inertia-related (IR) torques balance aerodynamic
  (Aero) torques, including torques exerted by
  zonal winds.
• Least squared solution minimize difference
  between IR and Aero torques assuming zonal winds
  for orbit batches.
• Requires Aero properties of s/c plus reaction
  wheel rates.
• Periapsis Coverage for Orbits 40-140 (MGS1)
• Ls 216-279 (before to 3-months after
  Noachis storm)
• H 120 km
• LAT 37-52N
• SLT16-12
• F10.7 70-90 (solar minimum)

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Westerly
Easterly
Southern Spring
Southern Summer
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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.

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MGCM-MTGCM Formulation, Parameters and Inputs

• 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.
• Fields passed upward at interface (T, U, V, Z) on
  2-min time-step intervals. No downward coupling
  enabled.
• Coupling captures upward propagating migrating
  non-migrating tidal oscillations, as well as
  in-situ solar EUV-UV-IR heating (migrating
  tides).
• Ls 90 (aphelion) and Ls 270 cases chosen.
• Empirical TES horizontal dust distributions
  (seasonal).
• Conrath parameter scheme used to specify vertical
  dust distributions (mixed to 40-50 km).
• Circulation sensitive to vertical dust (Bell et
  al. 2004)

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MTGCM Aphelion Case (Ls 90)Temperatures (K)
at SLT15 (MGS2)

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MTGCM Aphelion Case (Ls 90) Temperatures (K)
at SLT3 (MGS2)

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MTGCM Aphelion Case (Ls 90) MGS2Dynamical
Heating (K/day) SLT 3
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MTGCM Odyssey Case (Ls 270)SLT17
Temperatures versus Latitude

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MTGCM Odyssey Case (Ls 270)SLT3 Temperatures
versus Latitude

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MTGCM Odyssey Case (Ls 270) Dynamical Heating
(K/day) SLT 3

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MTGCM predictions at 120 km ?
Westerly
?
?
?
?
?
?
Easterly
Southern Spring
Southern Summer
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MTGCM Meridional Winds (m/s) MEX1(Aug. 2004
Ls 90 F10.7 100)
Min -122 m/s
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MTGCM Vertical Winds (m/s) MEX1(Aug. 2004 Ls
90 F10.7 100)
Max 1.0 m/s Min -1.25 m/s
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MTGCM Meridional Winds (m/s) MEX2(Aug. 2005
Ls 270 F10.7 100)
Max 134 m/s
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MTGCM Vertical Winds (m/s) MEX2(Aug. 2005 Ls
270 F10.7 100)
Max 1.2 m/s Min -2.3 m/s
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Mars Thermospheric Circulation

• Baird (2005) technique for extracting zonal
  winds from ACC is promising. Requires ACC with
  sensitivity at least as good as MGS.
• Simulation of thermospheric winds requires
  proper driving of Mars lower atmosphere with
  realistic horizontal and vertical dust
  distributions
• After Noachis dust storm
• Likely inter-annual variations in winter polar
  warming near Ls270.
• Mars thermospheric circulation, especially during
  solstices, can be traced by NO nightglow
  latitudinal density and temperature variations
• A stronger inter-hemispheric circulation is
  expected during perihelion than for aphelion
  conditions. Hemispheric differences expected in
  NO nightglow (stronger emission during Ls 270
  polar night).
• . Seasonal/hemispheric differences observed and
  simulated in winds aerobraking winter polar
  night temperatures (polar warming)