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Finding FingerprintsXDAP 16|11|2004 FINDING FINGERPRINTS Probing the interaction between comets and...
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Transcript of Finding FingerprintsXDAP 16|11|2004 FINDING FINGERPRINTS Probing the interaction between comets and...
Finding Fingerprints XDAP 16|11|2004
FINDING FINGERPRINTSProbing the interaction between
comets and the solar wind
Dennis Bodewits
Xander Tielens, Ronnie Hoekstra
KVI Atomic Physics
Zernikelaan 25, 9747 AA Groningen
Finding Fingerprints XDAP 16|11|2004
Cometary X-Ray emission
Features:
•Bright in 0.2-1000eV
•Line emission
•Variable
•Common property of (nearby) comets
Charge Exchange
Finding Fingerprints XDAP 16|11|2004
Interaction between comet and wind
•10 km Nucleus•103 km Contact surface•106 km Bowshock•108 km Tails
Oq+
photon
O(q-1)+
Finding Fingerprints XDAP 16|11|2004
Slow<400 km/s
Fast1000 km/s
Solar Wind
• Northern Light!!
• Per cm3: - 9 protons- 10 elektronen- 0.5 He2+
- few Oq+,Cq+,Nq+,…
• Windtypes
• Variability!
Finding Fingerprints XDAP 16|11|2004
Fingerprints of Charge Exchange
Photon(s)
Aq+ + B A(q-1)+(nl) + B+
Encke 2003
McNaught-Hartley
1999 S4 Linear
• Quasi resonant
• Excited state
• Molecules?
• Multiple EC?
Finding Fingerprints XDAP 16|11|2004
Photon emission spectroscopy
gas jet
nozzle
Ions from ECRIS
Faraday cup
spectrometer
Photon(s)
Aq+ + B A(q-1)+(nl) + B+
Finding Fingerprints XDAP 16|11|2004
Solar wind helium - experimental results
velocity (km/s)
0 250 500 750 1000 125010-2
10-1
100
101
102
line
ratio
H2O
H2
CO
He He+
Electron capture strongly depends on collision partner and velocity
Finding Fingerprints XDAP 16|11|2004
Sun
yR r
x
observer
Interaction model
atoms
Gas Production Q, Heliocentric Distance, Scale Lengths
molecules
1. Comet atmosphere
2. Charge state dist.
3. Image & spectrum
Finding Fingerprints XDAP 16|11|2004
Charge state distribution
Big comet•Cross section
•Density distribution
O8+
O7+
O6+
O8+
O7+What collisions? Depends on properties of wind AND comet
Small comet
O6+
Finding Fingerprints XDAP 16|11|2004
Model results II – synthetic spectra
Combination of composition + comet + cross sections
Aq+ + molecules?? Multiple electron capture??
Experiments!!!
200 300 400 500 600 700 800 900 10000
1
2
3
4
5
6
7
8
9
10x 10
23
Wavelength (eV)
Inte
nsity (
ph
oto
ns/s
/eV
)
Encke spectra due to fast SW Oq+, Cq+ and Nq+
OVIII np - 1s
OV
III 2
p -
1s
OVII np - 1s O
VII 2
p -
1s, O
VII [2s-1
s]
CV
I np
- 1
s
CV
I 2p
- 1
s, [2
s-1
s]
CV
np -
1s
NV
I 2-1
,[2
-1]
OVIIIOVIICVICVNVIINVIsum
Finding Fingerprints XDAP 16|11|2004
Example: CXO observations Comet Encke
• Collisionally thin coma • close to the sun• fast wind O8+
C6+ O7+
C5+
Finding Fingerprints XDAP 16|11|2004
velocity (km/s)
0 250 500 750 1000 125010-2
10-1
100
101
102
line
ra
tio
Summary
Spectra and morphology in x-ray and FUV depend on solar wind AND comet characteristics
Charge exchange emission strongly depends on collision partner and velocity
Provides excellent diagnostic tool, but….• need of laboratory data!• need of spatially resolved high res. spectra!
200 300 400 500 600 700 800 900 10000
1
2
3
4
5
6
7
8
9
10x 10
23
Wavelength (eV)
Inte
nsity
(ph
oto
ns/s
/eV
)
Encke spectra due to fast SW Oq+, Cq+ and Nq+
OVIII np - 1s
OV
III 2
p -
1s
OVII np - 1s
OV
II 2p
- 1
s, O
VII
[2s-
1s]
CV
I np
- 1
s
CV
I 2p
- 1
s, [2
s-1
s]
CV
np
- 1s
NV
I 2-1
,[2-1
]
OVIIIOVIICVICVNVIINVIsum