1. Reflected Solar Wind in the foreshock region of Venus observed by Venus Express
M. Yamauchi1, Y. Futaana1, R. Lundin1, S. Barabash1, M. Wieser1, A. Fedorov2, J.-A. Sauvaud2, T.L. Zhang3, W. Baumjohann3, J.D. Winningham4, R.A. Frahm4, E. Dubinin5, and M. Fraenz5.
(1) Swedish Institude of Space Physics, Kiruna, Sweden,
(2) Centre d’Etude Spatiale des Rayonnements, Toulouse, France,
(3) Space Research Institute, Graz, Austria
(4) Southwest Research Institute, San Antonio, Texas, USA
(5) Max-Planck-Institut fur Sonnensystemforschung, Katlenburg-Lindau, Germany
Characteristics of ions flowing upstream along IMF from the Venus bow shock (BS): Comparison to Earth and Mars

2. Summary
Venus Express / ASPERA-4 often observes nearly field-aligned beam-like protons (FAB) in the foreshock region of Venus (Fig. 1, Fig. 2) :
(1) They travel away from the quasi-parallel bow shock of Venus, nearly along the interplanetary magnetic field (Fig. 2, Fig. 3).
(2) About 2~6 times energy of the solar wind proton energy (Fig. 1).
(3) The protons are classified into two beams: (a) field-aligned beam in the SW frame of reference, and (b) field-aligned beam in Venus frame of reference which gyrates in the SW frame (Fig. 3). The combination forms a pancake-like distribution.
They are similar to those at the terrestrial foreshock region (Fig. 4). On the other hand, Mars Express, with the same instrumentation a Venus Express, does not observe the FAB in the Martian foreshock region. We instead observe effective perpendicular acceleration (Fig. 4) along the shock surface. The difference must come from the different gyroradii of the ions.

3. Fig 1: , ∑ 3-min scan SW SW SW SW BS BS BS BS Scan=-45°~45°
e- (top) & H+ (rest) at different angle

4. B B B B 2006-6-18 connected to BS 2008-10-28 connected to BS Fig 2:
Beam = foreshock
Sometimes no beam in foreshock
Fig 2:
Top: VEX trajectory (both approaching Venus) and projected IMF,
Middle: three components of IMF,
Bottom: H+ spectrogram at sectors where FAB is observed (cf Fig. 1)

5. Fig 3: pitch angle distributionSW SW SW
Fig 3: pitch angle distribution
FAB in the SW frame
FAB in the Venus frame SW

6. Mars ≠ Venus, but both // and  accel. are clear
Fig 4: other planets
Earth ≈ Venus, but f ≈ Maxwellian SW SW
V//
V//
cluster-3
cluster-1 V V
(Cao et al., 2008)

7. Fig 4b

8. Fig 3b

9. Fig 2b Y Z X X
BX, BY, BZ
not connected to BS