1. Mars, Venus, The Moon, and Jovian/Saturnian satellites
5th Alfvén Conference
on “Plasma Interaction with Non-magnetized Planets/Moons and its Influence on Planetary Evolution”
4-8 October, 2010
Sapporo, Japan
Mars, Venus, The Moon, and Jovian/Saturnian satellites

2. Bowshock and Planetary Size: a Earth-Venus-Mars comparison
M. Yamauchi et al., IRF-Kiruna
SW paraeter
BS size
nV2
(or PD) B
(or RG) MA
c/pi
Venus 1
Earth
~ 5
~ 0.7
~ 1.2
~ 2
Mars
~ 0.5
~ 1.4
~ 4
Gyroradius vs Bow-shock size

3. Bowshock / Foreshock = accelerated ions

4. Outline
1. Venus ≈ Earth
2. Mars ≠ Venus/Earth

5. Earth’s case = since 1970’s B
All data from cluster

6. Venus we show this , ∑ 3-min scan , ∑ 3-min scan , ∑ 3-min scanBS BS BS BS
e- (top) & H+ (rest) at different angle
Venus
we show this

7. Venus ≈ Earth B 2006-6-18 B FS connected to BS = FS SW (=1)
Top: VEX trajectory (both approaching Venus) and projected IMF,
Middle: three components of IMF,
Bottom: H+ spectrogram at sectors where FAB is observed. No integration over elevation
Localized in the sector 6. Middle part and boundary part.
SW (=1)
Scanning over -45°~+45°

8. IMA looking direction
VEX

10. cf. Earth
(Cao et al., 2008)
FS ion
* Upstream region
* Energized (> Esw)
* Localized (< few 100km)
V//
V// SW SW
cluster-3
cluster-1
Distance between c-1 and c-3 few hudreds km. FAB is very localized.
* f ≈ Maxwellian ? V V

11. Venus ≈ Earth How about Mars?
No internal magnetic field, no magnetosphere.
Planet is the same size as the Earth. 
Smaller bow shock size than the Earth, yet MHD regime.
How about Mars?
No internal magnetic field.
Planet is smaller than the Earth. 
The bow shock size is too small to treat with MHD
Max number difference

12. Mars Foreshock case
foot distance

13. Detail of spectrogram (E=1~15 keV)
 =4
 =3
 =2
 =1
ring H+
Each elevation scan. We deal with a ring distribution to define B field.
Several rings visible on the bottom panel

 =all
Mixture of accelerated ion (H+) components

14. 3rd // acc
2nd // acc
main // acc
pre-acc
heating

15. Classifying counts in // and  directions
Each point more than 5 counts.
Upper panel: v_perp. and v_paral
Bottom: in the B-filed
Yama claims that he checked blocking by the s/c. Second acc. Up to 900 km/s
B (N-direction) is estimated from minimum variance method applied to the ring distribution

16. 3rd // acc
2nd // acc
main // acc
pre-acc
heating

17. Two components 1. Field-aligned H+. 2. Gyrating H+ with large V//.
Both types are found in the Terrestrial foreshock
Venus: yes for entire upstream
Mars: foot only!

18. Special features for Mars
// beam observed only close to BS
Energy is stepping (due to reflection?)
Gyro-bunching effect (due to short distance?) with gradual  acceleration (why?)

19. Three possible configurations
and check multi-step acceleration (due to reflection)

20. Quasi- (case 1) B was obtained from ring distrubation.
Full elevation scan

21. Quasi-// (case 3) B was obtained from ring distrubation.
Full elevation scan

23. Summary
Venus Express / ASPERA-4 often observes back-streaming H+ in the foreshock region of Venus, in a similar ways as the Terrestrial foreshock, i.e., field-aligned component, and intermediate (gyrating) component
Mars Express / ASPERA-3 (same instrumentation as VEX) did not observe similar ions in the Martian foreshock region beyond the foot region. Instead, it shows different type of acceleration in the foot region, indicating the ion trajectory (history) during its gyromotion.
The finite gyroradii effect makes Mars a perfect laboratory to study acceleration processes.

24. End Red and Pink are clearly separated in energy Black --> red
Pink = accelerated to "discrete" energy.
Green (scatter) + green cross = // acceleration in unknown way.

25. PA dist.
 = 3~7 only
I projected features back to spectrogram (but this it probably to much for presentation)
SW co-aligned with B
Two populations: FAB and gyrating similar to earth.
Conöusion: venus is similar to the earth

26. Venus e- (top) & H+ (rest) at different angle , ∑ 3-min scan SW SW SWBS BS BS BS
Venus
Scan=-45°~45°

27. VEX connected by B not connected BS SW BS , ∑ 3-min scan
4 sectors (90° each) summed over the elevation scan. MAG data used. If connected there is a proton population. BS SW BS

28. Point here is the acceleration occurs in the same direction.

29. case 3a

30. case 3b