Charge Exchange in Comets off the beaten track

1. AAS/HEAD 2013 Charge Exchange in Cometsoff the beaten track Dennis Bodewits1, Damian Christian2, Casey Lisse3, Scott Wolk4, Konrad Dennerl5, Jenny Carter6, Andy Read6, and Susan Lepri7 (1) Univ. Maryland, College Park, (2) CSU Northridge, (3) JHU/APL, (4) CfA, (5) MPE Garching, Germany, (6) Univ. Leicester, UK, (7) Univ. Michigan

2. Outline • Charge Exchange occurs where a hot plasma meets a neutral gas. • How can we use other wavelength regimes? • How can we use comets to study CX emission in different plasma environments? • What will we learn with the next generation X-ray telescopes?

3. A High Energy View of Comets Comet Ions He+, He2+, O6+, .. Dust (Continuum) Atoms S, C, O, H Optical UV FUV EUV X-ray Energy Wavelength Molecules NH2, C3, C2, NH, OH, CS, H2 Heavy Ions C5,6+, O7,8+, .. Molecular ions CO+, H2O+, CO2+, .. Solar Wind

4. Simultaneous X-ray/UV image of a comet APOD Feb 21, 2009, Bodewits et al. 2010, Carter et al. 2011

5. 1. Other X-rays

6. C,N OVII OVIII Chandra Comet Survey H E X-ray spectra sample solar wind state low abundance of highly charged oxygen cold wind high abundance of highly charged oxygen  hot wind F G Solar wind freeze-in Temperature C A B D Bodewits et al. 2007

7. Temperature vs. Freeze-in Temperature Bodewits et al. 2012

8. Where is the Polar wind? Bodewits et al. 2007

9. Comet emission > 1000 eVC/2002 C1 (Ikeya-Zhang) + CME OVII and OVIII Ne IX Mg XI Ne X Mg XII Si XIII Fe XV - XX Bodewits et al. 2007; Ewing et al. 2013.

10. SWCX or artifact? Si Si XIII, XIV? Mg Mg XI, XII?

11. SWCX <300 eV: terra incognita • 73P/Schwassmann-Wachmann 3b • 0.1 AU in 2006 • Warm slow wind • Cross section? • Calibration around 300 eV? • CX emission from Mg, Si, Ne… • 90% of emission at 300 eV is NOT CV

12. SWCX <300 eV: terra incognita CHIPS+Chandra observations of Comet C/2001 Q4 (NEAT) SWCX Model Koutroumpa et al. 2008 Sasseen et al. 2006

13. Si and Mg as temperature probes Si Mg

14. 2.The UltraViolet: Helium Rules!

15. OVI: elusive SWCX emission • N(O6+) = ~10 – 20 x N(O7+) • OVI doublet around 103 nm • Doppler-shift measure SW velocity • Emission cross section comparable to OVII features (Bodewits & Hoekstra 2007). Increase 2-3x with velocity. • Fuse: non-detections in 3 comets (Weaver et al. 2002; Feldman et al. 2005). • 400x smaller FOV than CXO • Best target: high inclination comet in polar wind • Rosetta ALICE 103.1, 103.7 nm

16. Most abundant ions in SW emit in EUV: O6+ + H2O  O5+(nl) OVI Line Ratio 11.6 / 17.0 nm fast slow Bodewits & Hoekstra 2007

17. He2+ He+ 30.4 nm He 58.4 nm He: The Coolest Ion of Them All • 1 – 10% of SW • N(He) ~ 75 xN(O) • Cross sections 1/10th • Fully ionized • Giotto (Fuselier ‘91) • EUVE • He I 58.4 nm Hale-Bopp (Krasnopolsky et al. ‘97) • He II 30.4 nm Hyakutake (Krasnopolsky et al. ‘01) • Venus, Mars (Krasnopolsky & Gladstone ’05)

18. He II/He I Line Ratio He He+ Electron capture strongly depends on collision partner and velocity Bodewits et al (2004, 2006)

19. 3. The Next Generation

20. Existing Observations:XMM & Suzaku Archives SUZAKU - 73P XMM RGS – C/2000 WM1 Brown et al. 2010 Dennerl et al. In prep.

21. High resolution X-ray spectroscopy will reveal: features of minor species (Fe, Mg, Si) will allow direct measurements of the triplet/singlet ratios of CV and OVII may detect fluorescence features of molecules such as CO2 (Dennerl et al. 2006) may find continuum emission (5% of total – Krasnopolsky et al. 1997) Should have capabilities below 300 eV Imaging would be awesome! (not discussed here) Wide Field Imager at GSFC? Prospects of High Resolution Spectroscopy

22. C/2012 S1 (ISON)The Great Comet of 2013? Swift – Bodewits et al. 2013 Seiichi Yoshida

23. Thank You!