1. The Wakes and Magnetotails of Venus and Mars
R. Lundin and S. Barabash
Swedish Institute of Space Physics, box 812, S , Kiruna, Sweden
The ”hairiness” of a magnetotail
The plasma environment near Mars and Venus
Atmospheric escape from Mars and Venus
Evolutionary aspects of Venus and Mars

2. COMETS
after the greek
Aster kometes = ”hairy stars”

3. Hale-Bop magnetotail at different stages of ”hairyness”
”Hairiness”, the characteristics of a magnetotail
Hale-Bop magnetotail at different stages of ”hairyness”

4. Current Filaments in plasma tail of Comet Hale-Bop
Cometopause
High speed escape
Closeup view of filamentation
Current filament (flux rope) scale size ≈ electron gyroradii
Dust tail
Bow shock
Flux ropes

5. The Hairiness reflecting the characteristic filamentation of plasma in the wake of a volatile rich body interacting with the solar wind
narrow beams
KH-waves ?
Producing structured outflow
Disconnection
..... and long tails

6. Phobos-2 traversal of the inner martian magnetotail(1)

7. Phobos-2 traversal of the inner martian magnetotail(2)

8. Martian magnetospheric cavity
... filled with plasma of ionospheric origin
Molecular ions

9. Elliptic orbit magnetotail crossings

10. 3 consecutive circular orbits
(PP marked out)
1. Central tail O+ dominated
2. Increased O+ flux in flank boundary layer

11. Ionization+Acceleration at the Martian Bow Shock

12. Bow-shock ionization layer
(critical velocity ionization?)

13. Ionization+Acceleration at the Martian Bow Shock
Dissipation region

14. Energy-Mass (E/q - m/q) spectrogram plot illustrating the ion acceleration to equal energy independent of mass (right), and to equal velocities for all masses (left).

15. Mass-loaded ion pickup in the boundary layer
Same velocity
Same energy

16. Mars plasma outflow and the magnetotail
Solar Wind
Bow Shock
MLB
”Planetopause”
Tail/beamed outflow
Ion pickup

17. Mass-Loading in the boundary layer of Mars and Venus

18. Mars
Phobos-2
Venus
PVO

21. Volatile content: Earth, Venus, and Mars
Atmospheric pressure: 90 Bar (mainly CO2)
Venus surface: 4.5·1014 m2
Venus atmospheric mass: 4.1·1020 kg
CO2 inventory on Venus is about 4.5 times higher than
that on the Earth,
Volatile inventory on the Earth is 4.3 times higher than
that on Venus!
Mars
Atmospheric pressure: Bar (mainly CO2)
Mars surface: 1.5·1014 m2
Mars atmospheric mass: 1.0·1016 kg
Atmospheric loss, oxygen/hydrogen: ≈1 kg/s
=> Atmospheric lifetime: ≈200 million years (2·108 years)

22. CONCLUSIONS (1)
The wakes and magnetotails of Venus and Mars are (like comets) expected to be very structured and ”hairy”
The Martian magnetotail constitute a central tail with a ”lobe” and plasma sheet, enclosed in a region of heavy mass-loading of the solar wind, bordering the magnetosheath by a mass-loading boundary.
The magnetotails of Venus and Mars are mainly controlled by the solar wind, except for potential perturbations from magnetic ducts at Mars and the effects of Phobos and Deimos.
The flaring-angle of the tail boundary differs between Mars (≈3.5 RM at 10 RM) and Venus (≈2 RV and 10 RV). Bow shock flaring – virtually identical, i.e. ≈6.5 RM and ≈6.5 RV respectively.
The Bow shock at Mars is associated with an ”ionization layer”. Implications for the tail? Venus?

23. CONCLUSIONS (2)
The magnetotails of Mars and Venus are characterized by large ionospheric ion outflows. Two types of outflows are observed (Mars):
– Upward acceleration in the topside ionosphere + mass loaded
acceleration => energies ≈ ESW
– Pickup processes in the magnetosheath => velocities ≈vSW
The tail outflow due to direct solar wind scavenging at the topside ionosphere on Mars and Venus is substantial on a cosmogonic time scale.
BUT
More data is required to elucidate the magnetotail properties of Mars and Venus. A particularly urgent case is Venus, considering the (surprisingly) scant data available up to now.