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” www.ep.sci.hokudai.ac.jp/~alfven5 4-8 October, 2010 Sapporo, Japan 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 The ASPERA-4 experiment on board Venus Express quite often observes protons in the foreshock region of Venus. Characteristics of these ions are similar to those of the field-aligned beams (FAB) at the terrestrial foreshock region: they travel away from the quasi-parallel bow shock of Venus, nearly along the interplanetary magnetic field with a pancake-like perpendicular distribution, and the energy is about 2~6 times that of the solar wind proton energy. At the boundary of this FAB region in the Venus foreshock, we often observe two population with energy-pitch-angle dispersion. Unlike the Venus case, Mars Express, with the same instrumentation, does not observe the FAB region in the Martian foreshock region. We instead observe effective perpendicular acceleration. Therefore, this difference must come from the different gyroradii of the ions dictated by the different solar wind conditions observed between those near Venus and those near Mars. Europlanet 2009, TP3 (Tuesday 15/9/2009)

Foreshock = full of accelerated ions

Outline 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 Finite gyroradii effect for Mars

Earth’s case = since 1970’s B

Earth: * Moving upstream * Energized * f ≈ Maxwellian ? B Earth: (Oka et al., 2005) (Cao et al., 2008) * Moving upstream * Energized * Localized (by B) FAB * f ≈ Maxwellian ? V// V// SW SW cluster-3 cluster-1 V V

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.

connected by B VEX not connected , ∑ 3-min scan BS SW BS

Venus ≈ Earth B B foreshock 2006-6-18 connected to BS = foreshock SW Top: VEX trajectory (both approaching Venus) and projected IMF, Middle: three components of IMF, Bottom: H+ spectrogram at sectors where FAB is observed 2006-6-18 connected to BS = foreshock SW scan = -45°~+45°

pitch angle distribution SW SW SW FAB in the SW frame FAB in the Venus frame I projected features back to spectrogram (but this it probably to much for presentation) SW pitch angle distribution

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  Mixture of accelerated ion (H+) components  =all

B (N-direction) is estimated from MVM.

Special features for Mars // beam at only close to BS, and many with the same V as ring (V0=0)  accelerated ions even at upstream (no velocity filter?) Energy is stepping for // direction To examine the acceleration history, we superposed 9 scans

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

Summary Venus 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

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

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