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___ ___ __________ __ ____ ___ ____________ __ ______ __ ____ _____. Mikhail V. Medvedev (KU). In collaboration with V. Florinsky (UAH) G. Zank (UAH) T. Cravens (KU) I. Robertson (KU). HEA-08 Moscow 24.12.2008. Solar Wind Charge Exchange mechanism for X-ray emission.

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  1. ___ ___ __________ __ ____ ___ ____________ __ ______ __ ____ _____ Mikhail V. Medvedev (KU) In collaboration with V. Florinsky (UAH) G. Zank (UAH) T. Cravens (KU) I. Robertson (KU) HEA-08 Moscow 24.12.2008

  2. Solar Wind Charge Exchange mechanismfor X-ray emission • Solar wind: frozen-in solar coronal composition ~0.1% heavy ion Mq+ (O, N, C, Fe, Si, Ne, S, Mg…) • Interstellar neutrals H, He • Charge transfer collisions: Mq + + H  H+ + M (q-1) +* M (q-1) +*  M (q-1) + + hn (Cox 1998; Cravens 2000)

  3. A charge exchange collision (Cravens 2002)

  4. Solar Wind composition

  5. CX X-rays observations (comets) Soft x-rays EUV Optical MHD model (comet LINEAR: Lisse et al., 2001)

  6. CX X-rays obs. (long-term enhancements) Long-term enhancements: ROSAT SXB flux (red) correlates with the Solar Wind proton flux (blue) measured by IMP-8 spacecraft. Suggested mechanism: Charge Exchange (CX) of SW ions with ISM neutrals penetrating into the heliosphere. (Cravens, Robertson, Snowden 2001)

  7. Heliosphere model velocity field bow-shock heliopause termination shock Solar Wind density field (model by Florinsky & Zank)

  8. Stream lines and species evolution Using the model, we - compute SW stream lines - compute charge state evolution along stream lines for 45 minor ions - compute spectra For each species (i) and charge state (q) along path (s): D ni,q/D s = i,q+1 <g> nSW ni,q+1 - i,q <g> nSWni,q where g2 = vSW2+ vth2

  9. Species evolution He C N O Ne Mg Si S Fe nose • Species: • He2+ • C6+ … C4+ • N7+ … N5+ • O8+ ... O5+ • Ne9+ ... Ne4+ • Mg10+... Mg3+ • Si10+ ... Si5+ • S11+ ... S5+ • Fe13+ ... Fe7+ tail

  10. Collisional thickness effect 2 3 1 Example of ion evolution: Mg10+…...Mg3+

  11. Oxygen O8+ --> O7+ O7+ --> O6+ O6+ --> O5+

  12. Angular distribution of intensity MgIX MgX MgVIII MgVII OVI OVII OV OVIII

  13. The predicted spectra dominant x-ray lines all x-ray lines O6+ (1s2p --> 1s2) 568.4 eV O6+ (1s2s --> 1s2) 560.9 eV O7+ (2p --> 1s) 654 eV C5+ (2p --> 1s) 367.3 eV C5+ (4p --> 1s) 459.2 eV O6+ C5+ O7+

  14. Nose-Tail asymmetry XMM-Newton tail nose Chandra: E >200 eV Chandra tail nose

  15. CX X-ray background (ROSAT) “predicted” ROSAT 1/4keV map nose tail X-ray flux angular distribution 1/4keV 3/4keV Outer heliosphere CX contributes ~ 20-30% of the inner heliospheric x-ray emission. Total CX x-ray emission is about 50% of the SXB (ROSAT map: Snowden 1997)

  16. Outside view of the heliosphere (O-lines) OVIII…OVII…OVI…OV

  17. Outside view of the heliosphere (Ne-lines) NeVIII…NeVII…NeVI…NeV…NeIV

  18. Nose & Tail spectra nose tail Spectral differences are much more prominent (e.g. OVII line) than in the inside-out view

  19. Observations of Sun-like astrospheres For a solar-like star at 5 pc distance and 100 ks exposure: Chandra/ACIS (0.5" resolution, 200 cm2 effective area) 4 counts ASTRO-E2/XRS (2' res, 40 cm2) 1 count Constellation-X (5-15", 5000 cm2) 120 counts XEUS (2", 50000 cm2) 1200 counts Current upper limit: Proxima Centauri (Wargelin and Drake, 2002) a 2-sigma upper limit on the mass loss rate of 9 solar vs 0.2 expected (Woods et al. 2002).

  20. Summary X-rays are produced heliosphere by the SWCX mechanism: Highly charged solar wind ions encounter and exchange an electron with neutral atoms and molecules. The resultant lower-ionized species emits x-ray quanta when it transits to the ground state. Using numerical models of the heliosphere by Florinsky and Zank, we reconstruct the SW stream lines, determine CX evolution of minor solar ions, calculate transition rates and x-ray spectra in the range of 100 eV--1 keV. We further present the predicted soft x-ray background sky and surface brightness maps (for the inside-out and outside view, respectively), the composition evolution, the spectra in various viewing directions and the angular intensity graphs. We presented post-dictions for ROSAT and predictions for Chandra and XMM. We emphasize that CX diagnostic is a unique remote tool for studies of distant stellar systems, their stellar wind ion composition, temperature and velocity, the neutral density of the local interstellar medium. This is particularly important because other sources of information on these winds are very scarce. The best candidate sources are identified.

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