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Comparison of the Martian and Venusian Wakes Fedorov, CESR, Toulouse

Comparison of the Martian and Venusian Wakes Fedorov, CESR, Toulouse It is a statistical study made on the base of about 120 night-side orbits of VEX (2006 – 2007 years) and 130 orbits of MEX (2007). Instruments: Aspera-3/4 and magnetometer MAG.

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Comparison of the Martian and Venusian Wakes Fedorov, CESR, Toulouse

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  1. Comparison of the Martian and Venusian Wakes Fedorov, CESR, Toulouse It is a statistical study made on the base of about 120 night-side orbits of VEX (2006 – 2007 years) and 130 orbits of MEX (2007). Instruments: Aspera-3/4 and magnetometer MAG.

  2. The procedure to accumulate a proper statistics is very sophisticated. The brief description is as follows: 1. For VEX: for each orbit to define the proper frame where X is the SW velocity vector and Z is the -VxB vector. 2. For each point of the orbit to calculate the ion distribution function in the proper frame for H+ and heavy planetary ions. IMF vector is in XY plane, By is always positive Red : Sunward Bx Blue: Tailward Bx Small vectors show normalized Byz

  3. 3. Since some part of ion distribution function can be obstructed by S/C body, the averaged distribution function is accumulated for each spatial cell 0.1 X 0.1Rv over many orbits to fill the blind spots. Right: two images showing the 4pi sphere. Black – no instance measurements, Blue – there are measurements in this angular sector. Top panel shows an example of an angular distribution, and bottom panel shows the sampled angular distribution (instantaneous coverage). Left diagram – how the measured distribution and the angular sampling are integrated into a spatial cell.

  4. VEX statistics:

  5. Spatial distribution of the number density of H+ (left) and heavy ions (right) in midnight meridian (averaged in Y = +/-0.5 Rv) . Vertical axis is -VxB solar wind electric field.

  6. Spatial distribution of the velocity of H+ (left) and heavy ions (right) in midnight meridian (averaged in Y = +/-0.5 Rv) . Vertical axis is -VxB solar wind electric field.

  7. Spatial distribution of the number density of H+ (left) and heavy ions (right) in equator plane (averaged in Z = +/-0.3 Rv) . This plane contains Vsw (X axis) and Bsw. PS is clear seen in both species.

  8. Spatial distribution of the velocity of H+ (left) and heavy ions (right) in equator plane (averaged in Z = +/-0.3 Rv) . This plane contains Vsw (X axis) and Bsw.

  9. MEX statistics: Since there is no magnetometer onboard of MEX, I have used another approach to define the proper frame of reference: I inspected the plasma data profile for each orbit, and rotated the frame around X to get plasma topology more or less similar to Venus one. See an example on the next slide. I supposed that PS (bursty intense oxygen flow) should be always in midnight meridian.

  10. PS example. How to find a proper frame Jul 07, 2007

  11. RESULTS and comparison with Hall MHD simulation by Ma.

  12. Ion density in XZ MSE frame

  13. Ion velocity in XZ MSE frame + Ma (Hall)

  14. Ion density in XY MSE frame

  15. Ion velocity in XY MSE frame

  16. COMPARISION between MARS and VENUS wakes

  17. Comparison of heavy ions in midnight meridian ( XZ plane, averaged in Y = +/-0.5 Rplanet). • Upper two panels – VENUS • Low two panels – MARS • Left – number density • Right – Velocity • Contours – Ma's Hall MHD results • Note: • much broader spatial distribution of the Martian heavy ions • The absence of pick-up at Venus

  18. Comparison of heavy ions in equator plane (XY, averaged in Z = +/-0.3 Rplanet). • Upper two panels – VENUS • Low two panels – MARS • Left – number density • Right – Velocity • Contours – Ma's Hall MHD results • Note: • Hall MHD describes better Venusian heavy ions distribution. • the narrow distribution of N and broad distribution of V in the Venusian tail.

  19. Comparison of protons in midnight meridian ( XZ plane, averaged in Y = +/-0.5 Rplanet). Upper two panels – VENUS Low two panels – MARS Left – number density Right – Velocity Contours – Ma's Hall MHD results Note: Martian wake is much wider in the scale of the planet radius. Attention: MEX cannot see H+ < 300eV

  20. Comparison of protons in equator plane (XY, averaged in Z = +/-0.3 Rplanet). Upper two panels – VENUS Low to panels – MARS Left – number density Right – Velocity Contours – Ma's Hall MHD results Note: H+ plasmasheet seen in the upper left panel. Attention: MEX cannot see H+ < 300eV

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