1. Foreshock studies by MEX and VEX FAB: field-aligned beam FAB + FS: foreshock M. Yamauchi et al.

2. SW parameter BS size M A (  n 1/2 V/B) c/  pi (  n -1/2 ) r g (  V/B) Venus1111 Earth~ 5~ 1.2~ 1.7~ 2 Mars~ 0.5~ 1.4~ 3~ 4 Shock = Fluid nature Foreshock = Particle nature  Gyroradius/Inertia length vs Bow- shock size is an important factor 2 keV H + under 6 nT  r g = 1000 km 5/cm 3 H +  c/  pi = 100 km vs R Mars = 4000 km

3. 1. Earth 2. Venus (similar to Earth) future work : He++/H+ ratio 3. Mars (Different from Venus/Earth) future work : various shock Outline

5. * Upstream region * Large V // (& sunward) * Energized (> E sw )

6. (Cao et al., 2008) V // VV VV cluster-3cluster-1 SW FAB * Localized (< few 100km)

7. 1. solar wind, 2. newly born ion, 3. bow-shock cold ion

8. SW BS ∑ 3-min scan e- (top) & H+ (rest) at different angle SW BS ∑ 3-min scan we show this Venus (Venus Express)

9. Venus ≈ Earth B connected to BS = FS B

11. IMA looking direction VEX

12. SW

13. 1. Field-aligned H +. 2. Gyrating H + with large V //. Both types are ∆V // << V //, Two populations (same as Earth)

14. 1. solar wind, 2&3. bow-shock cold ion, 4. sneak out ∆V // << V // (yes), ∆V // << V // (yes), ∆V // ~ V // (no),

15. He++ and H+ show different behavior (future work)

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

17. (1) only "ring" distribution (2) no "foreshock" signature (examined ~ 500 traversals) BS Quite different from Venus:

18. If very close to bow shock

19. 3rd // acc 2nd // acc main // acc pre-acc heating

20. blue: primary ring red: 1st branch purple: 2nd branch brown: 3rd branch Multiple acceleration Gyro-phase bunching red: half gyro purple: one third gyro

21. 

22. Multiple-Reflection frameXYZ (MSO)LMN L (0, 0.55, -0.8)= (+1,0,0) M (-1.0, 0.15, 0.1)= (0,+1,0) N=-B/B (0.2, 0.8, 0.55)= (0,0,+1) n (0.6, -0.8, 0.)(-0.45, -0.7, -0.5) V SW /V SW = (-1, 0, 0)(0., 1.0, 0.2) V R /V SW (-0.3, -0.95, 0.)(-0.5, 0.15, -0.8) V HT /V SW (-1.2, -0.95, -0.6)(0., 1.0, -1.4) n: shock normal V R : specularly reflected SW x V HT : de Hoffman Teller (V’ SW // B) +M ~ +N

23. Multiple-Reflection +M ~ +N S E S: toward BS from left S&E: toward BS from left S ~ V HT = along BS E: along BS S: along BS E: toward BS E: toward BS from right (0.6, -0.8, 0) XYZ

24. SW Reflection  convert V  to V // in SW frame ∆∆

25. V // -V X V SW reflection gyration

26. 3rd // acc 2nd // acc main // acc pre-acc heating Time = Spatial variation

27. Classifying counts in // and  directions Time = Spatial variation

28. Three configurations (on-going work) 2005-7-29 2005-8-3 2005-7-12 2005-8-5 Done

29. 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?)

30. 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 gyroradius effect makes Mars a perfect laboratory to study acceleration processes.

31. End

32. Quasi-  shock (case 1)

33. Quasi-  and // (case 1+3)

35. Quasi-// (case 3)

37. case 3a

38. case 3b

39. Quasi-  (case 1+3)

40. 2006-6-182008-10-28 B connected to BS BBB Beam = foreshock connected to BS Sometimes no beam in foreshock Venus ≈ Earth

42. 5th Alfvén Conference 4-8 October, 2010 Sapporo, Japan www.ep.sci.hokudai.ac.jp/~alfven5 on “Plasma Interaction with Non- magnetized Planets/Moons and its Influence on Planetary Evolution” Mars, Venus, The Moon, and Jovian/Saturnian satellites