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

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

Bowshock / Foreshock = accelerated ions

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

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

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

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°

IMA looking direction VEX

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

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

Mars Foreshock case foot distance

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

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

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

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

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!

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?)

Three possible configurations and check multi-step acceleration (due to reflection) 2005-7-29 2005-7-12 2005-8-5

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

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

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.

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

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

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

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

Point here is the acceleration occurs in the same direction.

case 3a

case 3b