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Transcript of Catching Some Sun Catching Some Sun the interaction between comets and the solar wind Dennis...
Catching Some Sun
Catching Some Sunthe interaction between comets and the solar wind
Dennis BodewitsZoltàn Juhàsz, Xander Tielens*,
Reinhard Morgenstern, Ronnie Hoekstra
Atomic Physics Groningen, NL
* Kapteyn Astronomical Institute,
Groningen University, Groningen, NL
Catching Some Sun
Amazing!!
X-Ray and FUV emission due to electron capture from cometary neutrals by solar wind HCI
Outline:
• Intro: Comets, Solar Wind
• Atomic Physics• Model: Solar wind
Helium• Conclusion
How can you use the X-Ray/FUV emission to study the interaction between comets and the solar wind?
Catching Some Sun
Comets & the Solar Wind
• Nucleus produces water at ca. 3000 kg/s
• Gas is photo-ionized and/or -dissociated
• 10 protons, 10 electrons, 5% He2+ cm-3, some Oq+,Cq+,Nq+,Neq+…
• Origin determines composition and velocity
Slow<400 km/s
Fast1000 km/s
Catching Some Sun
The process: Charge Exchange
• Electron is captured into excited state (nl)• Over-the-Barrier Model: resonant electron
capture, n depends on q and Ib and v
• Cross sections: total, state selective
ion target ion targetQuasi molecule
photon
Catching Some Sun
Experiment: AGORA
• Wide velocity range• ECRIS allows for different projectiles: Heq+, Oq+, Nq+, …
• Different target gases possible: H, H2, CO, ..?
Perfect for the comet-solar wind system!
Catching Some Sun
Single electron capture
30.4 nm
He+ emission
He2+ + CO He+
!! 30.4 nm !!
Energy (keV/amu)
0.01 0.1 1 10
(
10-1
6 c
m2 )
0.01
0.1
1
10
Total – Ishii, Rudd(1s) – Kearns
(2p) - KVI
Catching Some Sun
Double electron captureHe2+ + CO He
58.4 nm
He emission
!! 58.4 nm !!
Energy (keV/amu)
0.01 0.10 1.00 10.00
0.1
1
10
(
10-1
6 cm
2 )
Total (Rudd, Cadez)
(2p) - KVI
Catching Some Sun
Observations vs. Experiments
•Line ratio indicates solar wind velocity•EUVE observations of Hale-Bopp and Hyakutake
CO
H2
He+ + X He(1s2p)
And by
Heq+ + H
Problem: contamination of ratio by
He2+
He+
He
30.4 nm
58.4 nm
Catching Some Sun
• Cometary model:– Gas production rate Q– Distance to Sun D– CO abundance
Comet-Solar Wind Helium Model
atoms molecules
He2+
He+He
Catching Some Sun
Results: Giotto probe
Halley:
Distance to Sun = 1 A.U.Q = 6*1029 s-1 contains 10% CO
Solar wind v = 300 km/sDistance to the Nucleus (km)
1e+41e+51e+6
He
+/(
He+
+ H
e2
+)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Catching Some Sun
Model parameters
•Solar Wind velocity: 50 km/s - 1100 km/s
•Gas production rate Q: 1027-1031 molecules/s
•Distance to Sun: 0.5 – 3 A.U.
•Composition: 0-100 % CO
The 30.4/58.4 ratio is a good velocity probe
Intensity 30.4 nm (Arb. Units)
Inte
nsi
ty 5
8.4
nm
(A
rb. U
nit
s)
Hale-Bopp 425 km/s; Hyakutake 220 km/s
Dv
COv
Q
Line ratio
Catching Some Sun
Conclusions & Outlook
• Helium line ratio is a powerful probe for solar wind velocity
• Helium line intensities cometary environment
• First investigation of FUV/X-ray; line ratios in HCI even more promising but data needed.
State selective cross section experiments are crucial for the interpretation of cometary FUV/X-Ray spectra
How can you use the X-Ray/FUV emission to study the interaction between comets and the solar wind?