Exosphere Temperature Variability
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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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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

Centre Nationale D'Etudes Spatiales,Toulouse, France

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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


Exosphere temperature variability at earth mars and venus due to solar irradiation

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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