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Charge Exchange Emission from Astrophysical Plasmas

Explore astrophysical plasmas' charge exchange emission using velocity-dependent cross sections and real data fitting techniques. Study CX in comets, starbursts, stellar winds, supernova shock rims, and more. Develop model in SPEX for ion composition and collision velocity. Address challenges in cross-section data incompleteness and population distribution.

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Charge Exchange Emission from Astrophysical Plasmas

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  1. Charge Exchange Emission from Astrophysical Plasmas Liyi Gu (SRON) T. Raassen (SRON), J. Kaastra (SRON, Leiden) X-ray from ion-neutral collision Velocity-dependent cross section Real data fitting: comet X-ray CHANDRA WORKSHOP 2015, CFA

  2. Charge Exchange Emission Zq+ + A Z*(q-1)+ (n,l,S)+ A+ Emission by radiative cascade

  3. Astrophysical CX Plasmas SWCX in comets geocoronal & heliospheric space Polar region of Jupiter North Polar Spur Wolf-Rayet stellar winds Supernova shock rims Starburst galaxies Cool core clusters

  4. CXModel in SPEX Assumptions Single electron capture with atomic hydrogen target (corrected for helium) Method Take all available cross section data σ(v, n, l, s) from literatures & databases Challenge: incompleteness esp. for n, l-population Derive the “scaling-law” v-dependent n and l distributions, apply to the missingions

  5. Method: n - distribution Resonance peak Velocity-dependent scaling law

  6. Method: l - distribution n < np n > np Rotation of internuclear axis determines lpeak l population evolves with v, n A new v, n(q)- dependent scheme + five basic weighting function

  7. S- Distribution G-ratio Triplet-to-Singlet Ratio (C5+ with H) Black: s-resolved Red: statistical weight Nolte+2012 Velocity (km/s) Higher order processes (e.g., electron-electron interaction) Calculated in very few cases Significantly affect the G-ratio at ~500 km/s

  8. Method: Radiative Relaxation Bodewits (2007) Highly excited p state to ground state transition (e.g., strong He-δ line) No up-excitation: 23S1-23P0,1,2 > 11S0-23P1,2 (forbidden line) CXmodel:lines fromradiative cascadeupton=16

  9. Characteristic Lines l-shell not fully implemented 0.3 keV 500 km/s OVIII Lyα OVII Heα SiXII 6 & 5->2 SiXII 6->2 NeIX Heα SiXII 5->2 OVIII Ly f NVII Lyα CVI Lyγ OVII He i f r CVI Lyβ β δ i NeX Lyα ε γ NVII Ly r δ β γ β δ γ Wavelength (Angstrom)

  10. Cometary X-ray C/2000 WM1, XMM-RGS CX fitting: 0.14 keV 290 km/s • Slow wind: 0.12-0.14 keV • ACE record: 280-350 km/s

  11. Summary Charge exchange creates forbidden-dominated and highshell-transition (e.g., He-δ, Ly-δ) spectra SPEX “CX” model: Velocity-, subshell- dependent cross sections Cascadecompleteupton=16 Applicabletomanyobjectsformeasuringion composition,ionizationtemperature,even collisionvelocity CHANDRA WORKSHOP 2015, CFA

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