Suprathermal C, N, and O atoms in the Martian upper atmosphere

1
Suprathermal C, N, and O atoms in the Martian
upper atmosphere
Valery I. Shematovich Institute of Astronomy,
Russian Academy of Sciences
2
Suprathermal heavy atoms at Mars
In collaboration with H. Lammer, H. Groeller, H.
Lichtenegger (Space Research Institute AAS, Graz,
Austria) M.N. Krestyanikova, M. Ya. Marov
(Institute of Applied Mathematics RAN, Moscow
) D.V. Bisikalo (Institute of Astronomy RAN,
Moscow )
3
Hot or suprathermal atoms

• Suprathermal atoms are formally defined as atoms
  with kinetic
• energies E gt 5 10 kT mean thermal energy of
  surrounding gas

Thermal processes
4
Hot or suprathermal atoms

• Suprathermal atoms are formally defined as atoms
  with kinetic
• energies E gt 5 10 kT mean thermal energy of
  surrounding gas

• Nonthermal processes
• induced by the energy
• Deposition.
• Suprathermals play an
• important role in
• atmospheric chemistry
• - UV emissions
• - atmospheric loss.

5
Hot or suprathermal atoms

• Suprathermal atoms (with kinetic energies E gt 5
  10 kT)
• are produced in the various nonthermal
  processes
• Photochemical sources dissociative recombination
  of molecular ions photon and electron impact
  dissociation exothermic chemical reactions
• Plasma sources charge exchange with and
  atmospheric sputtering by high-energy
  magnetospheric and/or solar wind ions

6
Hot atom kinetics
Suprathermal atoms loose their translational
energy in elastic and inelastic collisions with
the ambient atmospheric gas When suprathermal
atoms chemically differ from the ambient gas
these relaxation collisions lead to
thermalization of the primary suprathermal
particles. Usually this process is considered in
the linear approximation. In the case when A
B, the subsequent collisions with the ambient gas
lead to cascade formation of new hot atoms
because atoms of secondary origin may be
produced with the suprathermal energies (E  gtgt
kT) .
7
Kinetic Boltzmann equation
Distribution of suprathermal atoms in the
atmospheric rarefied gas is evaluated through
the solution of Boltzmann-type kinetic equations
with the source terms
8
Suprathermal heavy atoms at Mars
(from Lundin et al., 2004)
9
Suprathermal oxygen at Mars

• McElroy, Science, 1972.
• Nagy and Cravens, GRL, 1998.
• Ip, Icarus, 1988, GRL, 1990. - 1D MC
• Lammer and Bauer, J. Geophys. Res., 1991. - 1D MC
• Kim et al., J. Geophys. Res., 1998.
• Hodges, J. Geophys. Res., 2000, GRL, 2002. - MC
• Krestyanikova, and Shematovich, Solar System
  Res., 2005, 2006. 1D DSMC
• Cipriani et al., J. Geophys. Res., 2006. - 3D MC
• Chaufray et al., J. Geophys. Res., 2007. - 3D MC
• Johnson et al., Sp. Sci. Rev., 2008
• Valeille et al., Icarus, 2009 JGR, 2009, 2010. -
  3D DSMC
• Fox and Hac, JGR, 1997 Icarus, 2009, 2010. 1D
  MC
• Groeller et al., J. Geophys. Res., 2010 (subm.)
  -3D MC

10
Heavy suprathermals at Mars sources
Dissociative recombination of the molecular
ions XY(v) e ? X(x1,x2,) Y(y1,y2,) ?E
v vibrational excitation of the ion electronic
ground state xi, yj electronic excitation
states of the ion fragments ?E excess kinetic
energy for ion fragments ?EEDXY EXY(v) -
EX(xi) - EY(yj) It is important to know the
total and partial cross sections for DR in
dependance on collision energy.
11
Hot oxygen at Mars sources
Branching ratios for Ecoll 0 Petrignani
et al., 2005 Kella et al., 1997
v 0 v 1 v 2
v 0 v gt 0
O2 e ? O(3P) O(3P) 6.96 eV 0.265 0.073
0.02 0.22 0.25 O2 e ? O(3P) O(1D)
5.00 eV 0.473 0.278 0.764 0.42 0.39 O2 e ?
O(1D) O(1D) 3.02 eV 0.204 0.510
0.025 0.31 0.27 O2 e ? O(1D) O(1S) 0.80
eV 0.058 0.139 0.211 0.05 0.09
0.22, 0.42, 0.31, and 0.05 for v 0 0.28,
0.36, 0.23, and 0.13 for v gt 0
Used branching ratios
Fox and Hac, 2009
12
Dissociative recombination of O2 ion
Cross section and branching ratios versus
collision energy (Peverall et al., J. Chem.
Phys., 2001).
13
Energy distribution of hot O atoms formed in O2
DR
120 km altitude
200 km altitude
13
14
Kinetics of the suprathermal O atoms

• Elastic collision
• Quenching collision
• Release of energy 1.97 eV for the 1D state and
• 4.19 eV for
  the 1S state
• Inelastic collision

14
15
Total and differential cross sections
Differential cross sections for elastic
collisions of O(3P) O(3P)
Elastic cross sections for O(3P) O(3P)
collisions
Kharchenko et al., 2000
Kharchenko et al., 2000
Elastic cross sections for O(3P) N2 collisions
We use the O O cross sections for O collisions
with neutral background atoms.
Balakrishnan et al., 1998
15
16
Total and differential cross sections
Statistically averaged elastic cross sections for
N N2 collisions
Elastic CM differential cross sections for N N2
collisions
We use the N N2 cross sections for O collisions
with neutral background molecules.
16
17
Hot oxygen at Mars Energy Distribution Functions
(EDFs) for low solar activity - MEX conditions
Cold O atoms
Ip, Icarus 76, 135, 1988
Kim et al. JGR 103, 29339,1998
Krestyanikova and Shematovich, Sol. Syst. Res.
40, 384, 2006
Hot O atoms
(2.94.5) 1025 s-1
18
Hot oxygen at Mars Energy Distribution
Functions(EDFs)

• Calculated EDF solid lines
• Thermal EDF dashed lines
• Left vertical line shows the region of
  suprathermal energies
• Right vertical line shows the escape energy.
• It is seen that
• suprathermal tail is formed including the
  escaping flux (4.1 5.6)107 cm-2 s-1
• hot atoms with energies between vertical lines
  populate the hot corona.

LOW SOLAR ACTIVITY
19
Hot oxygen at Mars hot corona

• Thermal hot fraction at
• exospheric temperature
• T180 K (solar min.)
• Nonthermal hot fraction
• from O2 dissociative
• recombination and atmospheric sputtering.
• Comparison with
• Nagy Cravens 1988
• Lammer Bauer 1991.

Different height scales!
LOW SOLAR ACTIVITY
20
UV emissions in the upper atmosphere of Mars
comparison with SPICAM MEX observations (Chaufray
et al., JGR, 2008)
Brightness of OI 130.4 nm triplet in dependence
on exospheric temperature. Possible input of hot
oxygen corona? ASPERA-3 measurements of ENAs?
21
Hot carbon at Mars sources

• Fox and Hac, JGR, 1999.
• Nagy et al., J. Geophys. Res., 2001.
• Chaufray et al., J. Geophys. Res., 2007.
• Johnson et al., Sp. Sci. Rev., 2008

22
Hot nitrogen at Mars sources

• Fox and Dalgarno, JGR, 1983.
• Fox and Hac, J. Geophys. Res., 1997.
• Johnson et al., Sp. Sci. Rev., 2008

23
Suprathermal heavy atoms at Mars
23
EDF at 240 km altitude for low solar activity
24
Suprathermal heavy atoms at Mars
Density profiles for high and low solar activity
25
Escape fluxes and Loss rates for oxygen
Escape process Loss rate s-1
Ion pick up of O 2 x 1024 (MEX, Science, 2007)
Sputtering of O 3.5 x 1023 (LeblancJohnson, 2002)
Cool ion outflow 1025
Ion escape of CO2, O2 1024 (Lundin et al., 2008)
26
Timeline of atmospheric loss at Mars
27
Hot corona at Mars
28
Suprathermal heavy atoms at Mars Conclusions
At present time the atmospheric escape at Mars is
dominated by loss of suprathermal neutrals H,
C, N, and O. Suprathermal heavy atoms in the
Martian corona play an important role in the
Mars interaction with the solar wind. Models
are still strongly limited by a poor availability
of the data on differential cross sections for
the Oh, Ch CO2, N2, O2, O collisions at
energies below a few keVs. Hopefully, they will
be tested and improved when the new data on the
upper atmosphere of Mars will be available (MEX,
PhSRM, MAVEN,).
Thank you for the attention!