The Spectrum of X-Rays from Comet Hyakutake

Northrop, T. G.

doi:10.1006/icar.1997.5762

Cited by 17 publications

(4 citation statements)

References 9 publications

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“…Possible mechanisms for cometary x-rays included thermal bremsstrahlung associated with collisions of solar wind electrons with cometary neutral gas or dust (39)(40)(41)(42)(43)(44), microdust collisions (45), Kshell ionization of cometary neutrals by electron impact (46), scattering or fluorescence of solar x-rays by cometary gas or by small dust grains (46,47), and the solar wind charge exchange (SWCX) mechanism (48)(49)(50)(51)(52)(53)(54). In the thermal bremsstrahlung mechanism, fast electrons are deflected in collisions with charged targets, such as the nuclei of atoms, and emit continuum radiation (46).…”

Section: Proposed X-ray Mechanismsmentioning

confidence: 99%

X-ray Emission from Comets

Cravens

2002

Science

202

162

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The discovery of x-ray emission from comet Hyakutake was surprising given that comets are known to be cold. Observations by x-ray satellites such as the Röntgen Satellite (ROSAT) indicate that x-rays are produced by almost all comets. Theoretical and observational work has demonstrated that charge-exchange collisions of highly charged solar wind ions with cometary neutral species can explain this emission. X-ray observations of comets and other solar system objects may be used to determine the structure and dynamics of the solar wind.

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Section: Proposed X-ray Mechanismsmentioning

confidence: 99%

X-ray Emission from Comets

Cravens

2002

Science

202

162

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“…The Chandra X-ray Observatory (CXO) measured soft X-ray spectra from comet C/1999 S4 ( A large number of explanations for cometary X-rays were suggested following the discovery paper in 1996. These included thermal bremsstrahlung emission due to solar wind electron collisions with neutral gas or dust in the coma Dawson et al 1997;Northrop 1997;Northrop et al 1997;Uchida et al 1998;Shapiro et al 1999), microdust collisions (Ibadov, 1990;Ip and Chow, 1997), K-shell ionization of neutrals by electron impact (Krasnopolsky, 1997), scattering or fluorescence of solar Xrays by cometary gas or by small dust grains (Lisse et al 1996;Wickramasinghe andHoyle 1996, Owens et al 1998), and by charge exchange between highly ionized solar wind ions and neutral species in the cometary coma (SWCX) (Cravens 1997a;Häberli et al 1997;Wegmann et al 1998;Kharchenko and Dalgarno 2000;Kharchenko et al 2003;Schwadron and Cravens 2000). Early evaluation of these various mechanisms Krasnopolsky 1997;Lisse et al 1999) favored only three of them: the SWCX mechanism, thermal bremsstrahlung, and scattering of solar radiation from very small (i.e., attogram-10 -19 g) dust grains, with SWCX mechanism suggested as the dominant process.…”

Section: Cometsmentioning

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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“…These included thermal bremsstrahlung (German for "braking radiation") emission due to solar wind electron collisions with neutral gas and dust in the coma Dawson et al, 1997;Northrop, 1997;Northrop et al, 1997;Uchida et al, 1998;Shapiro et al, 1999), microdust collisions (Ibadov, 1990;Ip and Chow, 1997), K-shell ionization of neutrals by electron impact (Krasnopolsky, 1997), scattering or fluorescence of solar X-rays by cometary gas or by small dust grains Wickramasinghe and Hoyle, 1996;Owens et al, 1998), and by charge exchange between highly ionized solar wind ions and neutral species in the cometary coma (CXE) (Cravens, 1997a;Häberli et al, 1997;Wegmann et al, 1998;Kharchenko and Dalgarno, 2000;Kharchenko et al, 2003;Schwadron and Cravens, 2000). In the thermal bremsstrahlung mechanism, fast electrons are deflected in collisions with charged targets, such as the nuclei of atoms, and emit continuum radiation.…”

Section: Proposed X-ray Mechanismsmentioning

confidence: 99%

X-Ray and Extreme Ultraviolet Emission from Comet P/Encke 1997

Lisse

1999

Icarus

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The discovery of high energy X-ray emission in 1996 from C/1996 B2 (Hyakutake) has created a surprising new class of X-ray emitting objects. The original discovery and subsequent detection of X-rays from 17 other comets ( Table 1) have shown that the very soft (E < 1 keV) emission is due to an interaction between the solar wind and the comet's atmosphere, and that X-ray emission is a fundamental property of comets. Theoretical and observational work has demonstrated that charge exchange collisions of highly charged solar wind ions with cometary neutral species is the best explanation for the emission. Now a rapidly changing and expanding field, the study of cometary X-ray emission appears to be able to lead us to a better understanding of a number of physical phenomena: the nature of the cometary coma, other sources of X-ray emission in the solar system, the structure of the solar wind in the heliosphere, and the source of the local soft X-ray background.

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The Spectrum of X-Rays from Comet Hyakutake

Cited by 17 publications

References 9 publications

X-ray Emission from Comets

X-ray Emission from Comets

X-rays from solar system objects

X-Ray and Extreme Ultraviolet Emission from Comet P/Encke 1997

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