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

Charge Exchange in Cometsoff the beaten track

AAS/HEAD 2013

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?

A High Energy View of Comets

X-rayOptical

Dust (Continuum)

MoleculesNH2, C3, C2, NH, OH, CS, H2

Molecular ionsCO+, H2O+, CO2+, ..

Energy Wavelength

AtomsS, C, O, H

UV FUV EUV

IonsHe+, He2+, O6+, ..

Heavy IonsC5,6+, O7,8+, ..

Comet

Solar Wind

Simultaneous X-ray/UV image of a comet

APOD Feb 21, 2009, Bodewits et al. 2010, Carter et al. 2011

1. Other X-rays

Chandra Comet SurveyC,N OVII OVIII

A

B

C

D

E

G

F

H

X-ray spectra sample solar wind statelow abundance of highly charged oxygen cold windhigh abundance of highly charged oxygen hot wind

Bodewits et al. 2007

Sola

r win

d fr

eeze

-in T

empe

ratu

re

Temperature vs. Freeze-in Temperature

Bodewits et al. 2012

Bodewits et al. 2007

Where is the Polar wind?

OVII and OVIIINe X

Ne IX Mg XI

Mg XII

Si XIII

Bodewits et al. 2007; Ewing et al. 2013.

Fe XV - XX

Comet emission > 1000 eVC/2002 C1 (Ikeya-Zhang) + CME

Si

Mg

SWCX or artifact?

Mg XI, XII?

Si XIII, XIV?

• 73P/Schwassmann-Wachmann 3b• 0.1 AU in 2006• Warm slow wind

ACE Chandra

C6+/O7+ 2.1 ± 0.7 2.1 ± 1.0

C5+/O7+ 7.6 ± 3 87 ± 29

• Cross section?• Calibration around 300 eV?• CX emission from Mg, Si, Ne…

• 90% of emission at 300 eV is NOT CV

SWCX <300 eV: terra incognita

SWCX <300 eV: terra incognita

Sasseen et al. 2006

CHIPS+Chandra observations of Comet C/2001 Q4 (NEAT)

Koutroumpa et al. 2008

SWCX Model

Si

Mg

Si and Mg as temperature probes

2. The UltraViolet: Helium Rules!

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

Most abundant ions in SW emit in EUV: O6+ + H2O O5+(nl)

Bodewits & Hoekstra 2007

fast

slow

OVI Line Ratio 11.6 / 17.0 nm

• 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)

He2+

He+

He

30.4 nm

58.4 nm

He: The Coolest Ion of Them All

He II/He I Line RatioHe He+

Electron capture strongly depends on collision partner and velocity

Bodewits et al (2004, 2006)

3. The Next Generation

Existing Observations:XMM & Suzaku Archives

SUZAKU - 73P

Brown et al. 2010 Dennerl et al. In prep.

XMM RGS – C/2000 WM1

Prospects of High Resolution Spectroscopy

•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?

C/2012 S1 (ISON)The Great Comet of 2013?

Seiic

hi Y

oshi

da

Swift – Bodewits et al. 2013

Thank You!