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Exosphere Temperature Variability at Earth, Mars and Venus due to Solar Irradiation

Exosphere Temperature Variability at Earth, Mars and Venus due to Solar Irradiation. Jeffrey M. Forbes Department of Aerospace Engineering Sciences University of Colorado, Boulder, Colorado, USA Sean L. Bruinsma Department of Terrestrial and Planetary Geodesy

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Exosphere Temperature Variability at Earth, Mars and Venus due to Solar Irradiation

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  1. Exosphere Temperature Variability at Earth, Mars and Venus due to Solar Irradiation Jeffrey M. Forbes Department of Aerospace Engineering Sciences University of Colorado, Boulder, Colorado, USA Sean L. Bruinsma Department of Terrestrial and Planetary Geodesy Centre Nationale D'Etudes Spatiales,Toulouse, France International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  2. International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  3. Exosphere Temperature Variability at Earth, Mars and Venus Earth Mars Venus Solar Irradiation & Planetary Rotation 200-400K 50-120K 200 K • In-situ • Solar Tides Propagating • from Below 20-50K > 20-50K ? ? Solar Radiation Variability 800K 180K 40K • Long-term 50-100K 20-40K 20K • Solar Rotation • Day-to-day 20-40K ? ? ? ? Solar Wind Interaction 20-200K International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  4. 81-DAY MEAN EXOSPHERE DENSITY AT MARS, Normalized to 390 km and Derived from Precise Orbit Determination of MGS (370 x 437 km orbit; perigee -40º to -60º latitude, 1400 LT) Equinox Equinox S. Hemis. Summer N. Hemis. Summer 81-day mean F10.7 solar flux at 1 AU 81-day mean F10.7 solar flux at Mars (1.37-1.66 AU) 81-day mean density Note: Each density determination is made over 3-5 Mars days, and is a longitude average, so there is no possibility to derive longitude variability, e.g., as seen in MGS accelerometer data. International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  5. Fit for density (10-18 cm-3): Least-Squares Fit to Exosphere Temperature Derived from Observed Densities and DTM-Mars (Lemoine and Bruinsma, 2002) S. Hemis. Summer Equinox N. Hemis. Summer Equinox zonal mean dust optical depth ±30o latitude avg. International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  6. Mars Venus Earth Jacchia (1970) MGS Drag Analysis Kasprzak et al. (1997) PVO, Magellan NRLMSISE00 International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  7. Exosphere Temperature Variability due to the Sun’s Rotation Forbes, J.M., Bruinsma, S., Lemoine, F.G., Bowman, B.R., and A. Konopliv, Variability of the Satellite Drag Environments of Earth, Mars and Venus due to Rotation of the Sun, J. Spacecraft & Rockets, 44, 1160-1164, 2007. International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  8. Solar Irradiation & Planetary Rotation In-situ Thermal Tides at Mars & Earth Niemann et al., Earth Planets Space, 50, 785-792, 1998. Mars SSMAX T ~ 120K SSMIN T ~ 40K SSMAX T ~ 400K Earth SSMIN T ~ 200K International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  9. Exosphere Temperature Variability due to Sun-Synchronous Semidiurnal Solar Tides Propagating from Below Mars low dust Ls = 270 Earth Mars low dust Ls = 270 International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  10. 0 12 local time 24 Topographic/land-sea Modulation of Periodic Solar Radiation Absorption Gives Rise to Longitude-Dependent Tidal perturbations Diurnally-varying solar radiation ≈ 25 K max-min variation with longitude Diurnal amplitude of latent heating due to tropical convection International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  11. Mars Thermosphere Densities at 120 km, 1500 LT, Kg/m3 Longitudinal Structures Due to Vertically-Propagating Thermal Tides Modulated by Topography MGS Accelerometer Mars GCM, Moudden & Forbes, 2008 International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

  12. Conclusions Concerning Exosphere Temperature Responses of the Terrestrial Planets to Changes in Solar Irradiation • These exosphere temperature responses are determined by • Magnitude of incoming solar radiation (i.e., orbit) & heating efficiency • CO2 content, i.e., cooling efficiency • Dynamics, i.e., adiabatic cooling (ion drag on Earth) • Rotation rate of the planet • Solar radiative absorption and heating at lower altitudes, i.e., upward-propagating thermal tides • Modulating topography International Conference on Comparative Planetology: Venus – Earth – Mars, 11-15 May 2009, ESA-ESTEC

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