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ENA diagnostics of the solar wind interaction with planetary bodies Stas Barabash Swedish Institute of Space Physics (IRF), Kiruna, Sweden. Outline. ENA introduction Sci. objectives of planetary ENA imaging. What can one achieve by ENA imaging?

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  1. ENA diagnostics of the solar wind interaction withplanetary bodiesStas BarabashSwedish Institute of Space Physics (IRF), Kiruna, Sweden

  2. Outline ENA introduction Sci. objectives of planetary ENA imaging. What can one achieve by ENA imaging? • Global ion distribution inside magnetospheres: Mercury, Earth • Plasma distributions in the interaction region: Mars, Venus, MEX data • Outflowing planetary ions: Mars • Global neutral gas / dust distribution: Europe, Phobos torus, Saturn rings • Surface interaction. Sputtered ENAs. Precipitation maps: Mercury, Moon • Atmosphere interaction. Backscattered ENAs. Precipitation maps: Mars, MEX data • Global dynamics: Mercury, Earth Conclusion • Planetary ENA experiments • New frontiers for planetary ENA imaging

  3. Planetary ENA experiments (out side the Earth)

  4. A+ A+ A0 A0 B0 dust neutral gas A0 A+ B0 C0 A+ A+ surface / atmosphere surface (B) / atmosphere surface (B) / atmosphere ENA introduction (1) • No gravitation banding: E >> Eescape, i.e., Eescape(O) = 2.4 eV for Mars • Processes resulting in ENA production in planetary environments • Neutralization: charge - exchange on neutral gas and dust • Surface (upper atmosphere) interaction: backscattering, sputtering, and recoil Ion neutralization Surface / atmosphere interaction

  5. ENA introduction (2) • ENAs propagate as photons: imaging of populations resulting in ENAs • Neutralization (CX): • Advantages: Provides ion or neutral gas (dust) global distribution • Drawback: line-of-sigh integrals => inversion problem, extra assumptions • Surface interaction: • Advantages: Provides the integral flux at the surface (cm-2 s-1 eV-1), no inversion. Surface (upper atmosphre) works a display • Drawback: Loss spectral information

  6. ENA introduction. Non magnetized planets (3) • Direct interaction with the upper atmosphere/ionosphere: Venus/Mars. ENA diagnostic to reveal: • Morphology of the interaction region • Global dynamics of the interaction region • Precipitation onto the upper atmosphere (backscattering) • Direct interaction with the surface: Moon. ENA diagnostic to reveal: • Morphology of the interaction region • Space weather effects

  7. DIAGNOSTIC OF THE INTERACTION REGION MORPHOLOGY (MARS/VENUS)

  8. ENAs at Mars

  9. Shocked SW ENAs. NPI observations

  10. NPI ENA observations vs. simulations ENA signal

  11. Inversion results // Solar wind parameters (non-fitted) pars[0] = 2.5; // Solar wind proton density [#/cm^3] pars[1] = 400e3; // Solar wind speed [m/s] pars[2] = 10; // Solar wind temperature [eV] // Geometry parameters (fiitted) pars[3] = 0.1667; // alpha, magnetopause penetration pars[4] = 0.55; // x_0, Bow shock position [Rm] pars[5] = 1.35; // x_nose, magnetopause position [Rm]

  12. Futaana, et al, 2006

  13. Subsolar jet (cone) Futaana, et al, 2006

  14. Non-observation of O-ENAs • Oxygen ENAs have NOT been observed by ASPERA-3: fluxes below the instrument limit (2.5·104 cm-2 sr-1 s-1) Galli et al.,. 2006). • Scaling the escape rate gives Q(O+) < 1023 s-1. In agreement with the direct escape measurements.

  15. GLOBAL DYNAMICS

  16. Response to an interplanetary shock (1) Futaana, Barabash et al., 2006

  17. Response to an interplanetary shock (2) Futaana, Barabash et al., 2006

  18. Response to an interplanetary shock (3) Futaana, Barabash et al., 2006

  19. Response to an interplanetary shock (4) Futaana, Barabash et al., 2006

  20. ENA jet oscillations Oscillation periods: 50 and 300 sec Depth ~20-30% DT Grigoriev et al., Space Science Rev.,, 2006

  21. Diagnostic of the dynamics • Time scale of the interaction region reconfiguration against interplanetary disturbances. • Time scale of the local instabilities at the induced magnetospehere boundary / plasma oscillations in the magnetospheath.

  22. DIAGNOSTIC OF THE PLASMA PRECIPITATION

  23. Backscattering ENAs. Simulations (1) • Monte Carlo simulation of proton / ENA backscattering (Kallio and Barabash, 2000)

  24. Backscattering ENAs. Simulations (2) • Backscattering hydrogen velocity distribution (Kallio and Barabash, 2000) • Albedo ~60%, Energy loss ~40%

  25. Backscattered hydrogen (ENA albedo) Backscattering H-ENAs. ENA albedo • Precipitating particles (ENAs and protons) experience elastic and non-elastic (CX, excitation) collisions with the upper atmosphere gases (mostly O and CO2) • Kallio and Barabash (2001) predicted backscattering H atoms caused by hydrogen ENA precipitation onto the upper atmosphere. • ENA energy ≈ 0.6 x precipitating energy • ENA albedo≈ 0.6

  26. Backscattering H-ENAs. Observations (1) H-ENAs from subsolar region Backscattering H-ENAs

  27. Backscattering H-ENAs. Observations (2) 27 Feb. 1948 - 1958 160 ns H-ENAs from subsolar region. ENA jet • H atom Energy: Subsolar ENAs: 2.14 keV Backscattering: 1.36 keV • Compare with ~2 keV shocked solar wind as measured by IMA in the magnetosheath • Flux: (8 - 14)·106 cm-2 sr-1 s-1 Backscattering H-ENAs. ENA albedo 200 ns TOF, ns

  28. Backscattering H-ENAs. Precipitation maps • Backscattered ENAs flux is proportional to the precipitation flux and can be used to construct precipitation maps Precipitation map NPD1 - Dir0. Orbit 500. July 11 1840 - 1900 NPD FoV longitude - latitude coverage. Orbit 500. July 11 1840 - 1900

  29. DIAGNOSTIC OF THE INTERACTION REGION MORPHOLOGY (THE MOON)

  30. Sputtered atoms (Johnson and Baragiola, 1991)

  31. Minimagnetosphere (Lin et., 1998)

  32. Imaging magnetic anomalies FoV (channels) Orbit motion

  33. Sputtered atoms • Angular distribution does not depend on the impinging ion flux angular distribution (statistically). • Atoms are not affected by electromagnetic forces and gravitation (E >> Eescape = 1.7 eV for Fe). • Sputtered atoms: O, Na, Al, Si, K, Ca, Ti, Mn, Fe • Atom sputtering conserves stoichiometry - an analytical tool in the lab. • Thomson - Siegmund spectrum:

  34. DIAGNOSTIC OF SPACE WEATHERING (THE MOON)

  35. Space weathering • Space weathering: changing albedo (visible, IR) under space environment effects, e.g., particle and photon flux, mmicrometeor bombardment • Swirl - like albedo marking in Crisium impact basin antipodal region (Reiner Gamma region, Lin et al., 1988, Hood et al. 1999)

  36. ENA emissions at Mars: simulations and observations on Mars ExpressStas Barabash and Mats HolmströmSwedish Institute of Space Physics, Kiruna, Sweden

  37. ENA production at Mars • Charge - exchange on the exosphere (extended due to low gravity!) • Upstream solar wind • Shocked solar wind • Planetary oxygen ions • Backscattering of the solar wind protons

  38. CX SW ENAs. Simulations (1) • Typical morphology: neutral solar wind, ENA fluxes tangential to flow lines Bow shock The boundary Solar wind SW void Mars SW void CX: shocked solar wind on the exosphere CX: undisturbed solar wind on the extended exosphere Highest neutral gas density Plasma distribution?

  39. CX SW ENAs. Simulations (2) • Holmström et al., 2002

  40. CX oxygen ENAs. Simulations (1) • Oxygen ion distribution (Test partciles in the empirical model, Kallio, 1997; Barabash et al., 2002)

  41. CX oxygen ENAs. Simulations (2) • O - ENA fluxes 0.1 - 1.65 keV (Barabash et al., 2002) • Typical morphology: subsolar jet and tailward flux

  42. MEX ENA sensors NPD NPI

  43. MEX ENA observations • Global structure of the solar wind interaction region • Shape of the solar wind void (NPI, Herbert Gunell et al., 2005) • Subsolar ENA jet (NPD, Futaana et al., 2005) • Oscillations of the ENA jet (NPD, Futaana et al., 2005) • Solar wind - atmosphere interaction • Occultation of the neutral solar wind at Mars (NPI, Klas Brinkfeld et al., 2005) • Solar wind proton precipitation onto the atmosphere: ENA albedo (backscattered ENAs) (NPD, Futaana et al., 2005) • Oxygen ENAs are not yet identified in the available data.

  44. Ion distributions inside magnetospheres. Pretty ENA images Earth’s ring current, from below Astrid-1 / PIPPI, C:son Brand et al., 2001 Earth’s ring current, outer vantage point IMAGE / HENA, courtesy D. Mitchell, APL Mercury magnetosphere, 30 keV protons, polor vantage point, Simulations, Barabash et al., 2001 Earth’s ring current, low altitude polar vantage point Astrid-1 / PIPPI, Barabash et al., 1999

  45. Ion distributions inside magnetospheres. Science • Ring current physics • Dynamics • Global morphology during different conditions • Composition (H, He, O) variations • Storm / substorm relations • Ion dynamics during substorms injections • Plasma sheet depolarization • M - I coupling (from deduced ion distribution) • Microphysics though P/A distribution reconstruction. Yet, it requires high angular resolution IMAGE / HENA Movie, courtesy Pontus C:son Brandt, APL

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