of X-ray Emission V. Kharchenko ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge 1. Introduction - interaction between the solar/stellar wind and neutral gas - X-rays induced in the charge-exchange (CX) collisions - CX mechanism of X-ray emission from the Jupiter atmosphere 2. X-ray spectra induced by CX collisions - selective population of excited states of highly charged ions - X-ray and EUV radiative cascading spectra - diagnostic of ion compositions and velocities 3. Conclusions. Acknowledgments to my coauthors: Alex Dalgarno Ron Pepino Rosine Lallement Matt Rigazio
Transcript
Charge-Exchange Mechanism of X-ray Emission
V. Kharchenko ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge
1. Introduction- interaction between the solar/stellar wind and neutral gas - X-rays induced in the charge-exchange (CX) collisions- CX mechanism of X-ray emission from the Jupiter atmosphere
2. X-ray spectra induced by CX collisions - selective population of excited states of highly charged ions - X-ray and EUV radiative cascading spectra - diagnostic of ion compositions and velocities
3. Conclusions.
Acknowledgments to my coauthors:Alex DalgarnoRon PepinoRosine LallementMatt Rigazio
X-ray ImageX-ray Image of Comet C/Linear 1999of Comet C/Linear 1999
Lisse et al. , Lisse et al. , Science (2001)Science (2001)
Sun
visual light
X-rays
X-ray Image of Comet McNaught-HartleyKrasnopolsky et al. (2002)
observed with the Chandra X-ray telescope
EUV X-ray
Krasnopolsky et al. (2001) Lisse et al. (2001)
hν
ROSAT data
Photon Energy [keV]
OVII (23S --11S) 561eV
Interaction between the Solar Wind and Neutral Gases in the Heliosphere
PlanetaryPlanetaryAtmospheresAtmospheres
Cometary Cometary AtmospheresAtmospheres
Interstellar gasInterstellar gas
Z q+ + A Z*(q-1) + A+
X-ray Photons
Cravens
(1997)
fast solar wind
slow wind
H2OH
H
He
O
Zq+ = O7+, C6+ , N7+ , Fe13+, Mg10+ …
X-ray emission from the polar regions of the Jupiter atmosphere
Precipitation of energetic ions Oq+ and Sq+
into the Jupiter atmosphere.
Ion energies: < MeV/amu Highly charged ions are produced by stripping collisions
between precipitating magnetospheric ions and atmospheric atoms (molecules):
I : Oq+ + H O(q+1)+ + e + H
II : O(q+1)+ + H O(q+2)+ + e + H
………………………..
N: O(q+n)+ + H O*(q+n-1)+ + H+ Magnetospheric ions
Magnetic field
Oq+Sq+
h
Charge-Transfer Collisions
nucleus
Dust particles
hν H
Oq+
hν
Aq+ + B A*(q-1)+ + B+
electron
Photon energy h
Volume Emission Rate:W = ng nions vi σ P
photon yieldcollision rate
minor SW ions:
Number of photons
(hν)
O
H
H2O
Oq+, Cq+ , Feq+ ...
H+ and He2+
Emission Spectra of Oxygen Ions
O(q+1)+ + H O*q+ + H+
X-rays induced by O*7+ ions in collisions of O*8+ with He atoms
2p - 1s
EUV CASCADING PHOTONS
180 220 260
180 220 260
Å
Å
EXPERIMENT
THEORY
C5+ + H2 C*4+ + H2+
C*4+
WAVELENGTH
Suraud et al.,1991
H2O
POPULATION OF ION EXCITED STATESIN ELECTRON-CAPTURE COLLISIONS
Neutral atoms and moleculesCO, O, He, H
n-2
n-1nion core
X-ray photon
hν
Multiplet Structure of Electronic States
Singlet states S=0 Triplet states S=1
s p d f s p d f
GROUND STATE Helium-like ions: C4+ , N5+ , O6+
23P
23S metastable state
n
electron
4
2
3
1
t = 0.001s L= 400m
O*6+ emission spectra detected in ion beam experiments [Greenwood et al. (2001)]
Theoretical spectra: photon cascading [Kharchenko et al.(2003) ]
{n,L} state-selective populations from the recoil-momentum spectroscopy measurements [Hasan et al. (2001)]
Solar WindElectrons and Ions
Minor IonsOq+: O5+ O6+ O7+ O8+
Cq+: C4+ C5+ C6+
Neq+: Ne7+ Ne8+
Nq+: N6+ N7+
andFeq+ Siq+ Mgq+ ….
(q = 6 - 16)
Ion velocity: ~ 300 – 1000 km/s slow fast solar wind
Major Ions H+ and He 2+
Total EUV and X-ray Emission Spectra
Total Spectra = i (Spectra of Individual SW Ions)
P(h
P(h) – number of photons per SW ion [eV-1]
Ne*8+
Sensitivity of EUV and X-ray spectra to the ion velocity V :
collisions : C6+ + H
R1R2
R1 : R2 = Function[v]
EUV X-ray
Spectra of CX Emission Induced by the Slow Solar Wind from H and He gas
Brightness Distribution in the Heliospheric Ecliptic Plane
H and He
H
He
CONCLUSIONS
• The CX mechanism successfully describes the observed spectra and intensities of the EUV and X-ray cometary emission.
• The CX collisions of the SW ions with the interstellar H and He gas are an important local source the diffuse X-ray background.
• Ion composition of the solar wind has been determined from the cometary X-ray emission spectra.
• Relative intensities of the cascading emission lines provide unique information on the composition and velocities of heavy ions in astrophysical plasmas.
X-ray Emission from the direction of the dark Moon
B.Wargelin et al. (2004)
SunMoon
Earth
SW ion
Spectra of X-Ray emission from two Comets
McNaught-Hartley
Linear S4Lisse et al. (2001)
Krasnopolsky (2004) Chandra X-ray telescope
Theoretical Models for O 8+ + H
Emission Spectra of O*7+ Ions
Emission Spectra ( Ion Beam Experiments )
O*6+
X-ray emission spectra of Ne*9+
Slow collisions Ne10+ + Ne
O6+ Emisson Beiersdorfer et al., Science (2003)
O7+ + CO2
23S -11S
23,1P- 11S
Laboratory Simulations of Cometary
X-ray Spectra Beirsdorfer et al. Science, 2003
Theoretical Models for O 8+ + H
Emission Spectra of O*7+ Ions
Velocity Dependent Spectra of Cascading
Emission of O* 7+ Ions
Theoretical and Experimental Spectra
NeNe10+10+ + H + H22O -> Ne*O -> Ne*9+9+ + H + H22OO++
SW Velocity Diagnostic form EmissionSpectra of the Soft Cascading Photons
O6+ Emisson Beiersdorfer et al., Science (2003)
O7+ + CO2
23S -11S
23,1P- 11S
Photon Emission Rate and Rate of Charge Transfer Collisions R
SunCollisional Depth =1Collisional Depth =1
= 3= 3
SW Ions
O 5+ + H + H2O, H, O …O, H, O …
Example: O5+
O8+
O5+
O7+
O6+
O5+, , O6+ ,, O7+ , and , and O8+
= 2= 2
R
Emission of Emission of O*4+ ions ions
100eV100eV
Heliospheric Emission :SW Ion Spectra from H and He gas
