5th Alfvén Conference

4-8 October, 2010Sapporo, 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

Reflected solar wind in the foreshock region:

a Venus-Mars comparison by VEX and MEX

M. Yamauchi1, Y. Futaana1, S. Barabash1, R. Lundin1, A. Fedorov2, C. Mazelle2, J.-A. Sauvaud2, J.D. Winningham4, R.A. Frahm4, T.L. Zhang3, W. Baumjohann3, E. Dubinin5, and M. Fraenz5.

(1) IRF, Kiruna, Sweden, (2) CESR, Toulouse, France, (3) SwRI, San Antonio, USA, (4) OEAW, Graz, Austria,(5) MPS, Göttingen, Germany

Europlanet 2009, TP3 (Tuesday 15/9/2009)

Foreshock = full of accelerated ions

1. Introduction = Earth's knowledge

2. Venus (similar to Earth)

3. Mars (Different from Venus/Earth)But it gives some hint on the acceleration process

Outline

B

Earth’s case= since 1970’s

Earth:

(Oka et al., 2005)

* Moving upstream

* Energized

* Localized (by B)

(Cao et al., 2008)

V// V//

V V

cluster-3 cluster-1

SW SW

FAB

B

Venus (Venus Express)

No internal magnetic field.

Planet is the same size as the Earth.

Smaller bow shock size than the Earth, yet MHD regime.

, ∑

3-m

in s

can

SW BS

VEXconnected by B not connected

BS

2006-6-18

B

connected to BS= foreshock

B

Venus ≈ Earth

foreshock

scan = -45°~+45°

SW

FAB in the SW frameFAB in the Venus frame

pitch angle distribution

SW SWSW

SW

Mars (Mars Express)

No internal magnetic field.

Planet is the smaller than the Earth.

The bow shock size is too small to treat with MHD.

Mars = weak & complicated

Detail of spectrogram (E=1~15 keV)

=4

=3

=2

=1

=allMixture of accelerated ion (H+) components

B (N-direction) is estimated from MVM.

// beam at only close to BS, and many with the same V as ring (V0=0)

accelerated ions even at upstream (no velocity filter?)

Energy is stepping for // direction

Special features for Mars

To examine the acceleration history, we superposed 9 scans

accel.

accel.

gyrate.

SummaryVenus Express / ASPERA-4 often observes nearly field-aligned beam-like H+ (FAB) in the foreshock region of Venus: * They travel away from QL bow shock of Venus, along IMF. * About 2~6 times energy of the SW H+ energy.

They are similar to those at the terrestrial foreshock region. * Combination of two beams forming a pancake-like distribution:

(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.

Mars Express / ASPERA-3 (same instrumentation as VEX) observed less intense but more complicated zoo of accelerated ions in the Martian foreshock region. The observation suggests the history of the acceleration.

The finite gyroradii effect makes Mars a perfect laboratory.

Mars case 2: 2005-6-3

case 2

Mars case 3: 2005-8-5

case 3a

case 3b

Mars case 4: 2005-8-3

case 4

2006-6-18 2008-10-28

B

connected to BS

B B B

Beam = foreshockconnected to BS

Sometimes no beam in foreshock

Venus ≈ Earth

Sca

n=

-45°

~45

°

SW SW SW

SW

BS BS BSBS

, ∑

3-m

in s

can

e- (top) & H+ (rest) at different angle

Venus