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Bliek, F.W.; Woestenenk, G.R.; Hoekstra, Ronnie; Morgenstern, R.

doi:10.1103/physreva.57.221

Cited by 28 publications

(18 citation statements)

References 18 publications

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“…No direct measurements or calculations of the triplet/singlet ratio have been performed for cometary neutrals though experiments have been undertaken for O 3+ +H 2 (Beijers et al, 1996) and N 4+ +H 2 (Bliek et al, 1998) which show only a slight decrease in the ratio below 3. We have carried out a QMOCC calculation for O 3+ +H 2 , but find that the ratio exceeds 4 .…”

Section: The Triplet-singlet Ratiomentioning

confidence: 99%

X-ray and extreme ultraviolet emissions from comets

2004

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There is significant progress in the observations, theory, and understanding of the x-ray and EUV emissions from comets since their discovery in 1996. That discovery was so puzzling because comets appear to be more efficient emitters of x-rays than the Moon by a factor of 80 000. The detected emissions are general properties of comets and have been currently detected and analyzed in thirteen comets from five orbiting observatories. The observational studies before 2000 were based on x-ray cameras and low resolution (E/δE ≈ 1.5 -3) instruments and focused on the morphology of xrays, their correlations with gas and dust productions in comets and with the solar x-rays and the solar wind. Even those observations made it possible to choose uniquely charge exchange between the solar wind heavy ions and cometary neutrals as the main excitation process. The recently published spectra are of much better quality and result in the identification of the emissions of the multiply charged ions of O, C, Ne, Mg, and Si which are brought to comets by the solar wind. The observed spectra have been used to study the solar wind composition and its variations. Theoretical analyses of x-ray and EUV photon excitation in comets by charge exchange, scattering of the solar photons by attogram dust particles, energetic electron impact and bremsstrahlung, collisions between cometary and interplanetary dust, and solar x-ray scattering and fluorescence in comets have been made. These analyses confirm charge exchange as the main excitation mechanism, which is responsible for more than 90% of the observed emission, while each of the other processes is limited to a few percent or less. The theory of charge exchange and different methods of calculation for charge exchange are considered. Laboratory studies of charge exchange relevant to the conditions in comets are reviewed. Total and state-selective cross sections of charge exchange measured in the laboratory are tabulated. Simulations of synthetic spectra of charge exchange in comets are discussed. X-ray and EUV emissions from comets are related to different disciplines and fields such as cometary physics, fundamental physics, x-rays spectroscopy, and space physics.

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Section: The Triplet-singlet Ratiomentioning

confidence: 99%

X-ray and extreme ultraviolet emissions from comets

2004

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“…Those that have been observed in the laboratory typically fall into the extreme ultraviolet or visible range. For example, a variety of such lines have been employed as diagnostics in tokomaks (Stratton et al 1990;von Hellermann et al 1995;Whyte et al 1998), and the crossed-beam technique has been used to study the emission from lithium-like or beryllium-like ions in the extreme ultraviolet regime (Bliek et al 1998;Lubinski et al 2000;Ehrenreich et al 2005). These systems are close analogs to the hydrogen-like and helium-like ions.…”

Section: L-shell X-ray Spectramentioning

confidence: 99%

X-rays from solar system objects

Bhardwaj

Elsner²,

Gladstone³

et al. 2007

Planetary and Space Science

136

115

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During the last few years our knowledge about the X-ray emission from bodies within the solar system has significantly improved. Several new solar system objects are now known to shine in X-rays at energies below 2 keV. Apart from the Sun, the known X-ray emitters now include planets (Venus, Earth, Mars, Jupiter, and Saturn), planetary satellites (Moon, Io, Europa, and Ganymede), all active comets, the Io plasma torus (IPT), the rings of Saturn, the coronae (exospheres) of Earth and Mars, and the heliosphere. The advent of higher-resolution X-ray spectroscopy with the Chandra and XMM-Newton X-ray observatories has been of great benefit in advancing the field of planetary X-ray astronomy. Progress in modeling X-ray emission, laboratory studies of X-ray production, and theoretical calculations of cross-sections, have all contributed to our understanding of processes that produce X-rays from the solar system bodies. At Jupiter and Earth, both auroral and non-auroral disk X-ray emissions have been observed. X-rays have been detected from Saturn's disk, but no convincing evidence of an X-ray aurora has been observed. The first soft (0.1- 2 keV) X-ray observation of Earth's aurora by Chandra shows that it is highly variable. The non-auroral X-ray emissions from Jupiter, Saturn, and Earth, those from the disk of Mars, Venus, and Moon, and from the rings of Saturn, are mainly produced by scattering of solar X-rays. The spectral characteristics of X-ray emission from comets, the heliosphere, the geocorona, and the Martian halo are quite similar, but they appear to be quite different from those of Jovian auroral X-rays. X-rays from the Galilean satellites and the IPT are mostly driven by impact of Jovian magnetospheric particles. This paper reviews studies of the soft X-ray emission from the solar system bodies, excluding the Sun

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“…We furthermore assume that capture by H-like ions leads to a statistical triplet to singlet ratio of 3:1, based on measurements by Suraud et al (1991); Bliek et al (1998). We will first focus on the strongest emission features, which are the n = 2 → 1 transitions, i.e., the Ly-α transition (H-like ions) or the forbidden, resonance and intercombination lines (He-like ions).…”

Section: Emission Cross Sectionsmentioning

confidence: 99%

Spectral analysis of theChandracomet survey

Bodewits

Christian²,

Torney³

et al. 2007

A&A

Self Cite

102

131

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Aims. We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and acis spectrometer in the 300-1000 eV range. Methods. The interaction model is based on state selective, velocity dependent charge exchange cross sections and is used to explore how cometary X-ray emission depend on cometary, observational and solar wind characteristics. It is further demonstrated that cometary X-ray spectra mainly reflect the state of the local solar wind. The current sample of Chandra observations was fit using the constrains of the charge exchange model, and relative solar wind abundances were derived from the X-ray spectra. Results. Our analysis showed that spectral differences can be ascribed to different solar wind states, as such identifying comets interacting with (I) fast, cold wind, (II), slow, warm wind and (III) disturbed, fast, hot winds associated with interplanetary coronal mass ejections. We furthermore predict the existence of a fourth spectral class, associated with the cool, fast high latitude wind.

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State-selective electron-capture measurements forN4+-H andN4+<

Cited by 28 publications

References 18 publications

X-ray and extreme ultraviolet emissions from comets

X-ray and extreme ultraviolet emissions from comets

X-rays from solar system objects

Spectral analysis of theChandracomet survey

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