Introduction:

With the advent of new Mars Global Surveyor aerobraking data (F10.7 = 80-150) and Neutral Mass Spectrometer observations from Planet-B (Nozomi) (F10.7 = 70-100), MTGCM constraints will exist for various seasonal, solar, and Mars dusty atmosphere conditions. A benchmark suite of non-dusty MTGCM cases for F10.7 = 68, 130, and 200 near Ls = 0 (Equinox), Ls = 270 (Southerm Summer Solstice), and Ls = 90 (Northern Summer Solstice) periods is given for reference. It is clear that significant differences exist in the simulated MTGCM fields over the Mars orbit, due solely to its large eccentricity.

The figure below shows Mars Ls versus heliocentric distance. Spacecraft seasonal and solar cycle sampling of the Mars upper atmosphere to date. Solar cycle minimum (min, filled diamonds), moderate (mod, triangles) and maximum (max, squares) observations are indicated.


Mars LS vs. Heliocentric Distance

Mars Spacecraft Observations of the Upper Atmosphere
Spacecraft Date(s) F10.7 Ls Dsm SZA Texo
M4
M6
M7
650715
690731
690805
77.0
167.0
188.0
139.0
200.0
203.0
1.553
1.425
1.425
67.0
0-44.0
0-44.0
212.0
315-350.0
315-350.0
M9N
M9E
71FALL
72SPRG
103.0
100.0
306.0
38.0
1.440
1.630
50-60.0
70-90.0
325.0
268.0
VL1
VL2
760720
760903
69.0
76.0
96.0
117.0
1.647
1.612
44.0
44.0
186.0
145.0
MPF 970704 70.0 143.0 1.557 135.0 153.0
MGS1
MGS2
980116
981027
93.0
127.0
256.0
48.5
1.382
1.653
73.5
57.0
220.0
235.0


F10.7 refers to the 10.7-cm index used to select reference EUV/UV flux datasets; Ls refers to the angular measure of the Mars seasons (Ls = 90 is Northern Summer Solstice, Ls = 270 is Southern Summer Solstice, etc.); Dsm refers to the Mars heliocentric distance (AU); SZA refers to solar zenith angle; T-exo refers to exospheric temperature. Dates are listed as follows: YYMMDD. Spacecraft are indicated as follows; M4 (Mariner 4), M6, M7 (Mariner 6 and 7), M9E (Mariner 9 Extended), M9N (Mariner 9 Nominal), VL1 (Viking Lander 1), VL2 (Viking Lander 2), MPF (Mars Pathfinder), MGS1 (Mars Global Surveyor Phase 1 Aerobraking sample), MGS2 (Mars Global Surveyor Phase 2 Aerobraking sample).