Negative ions in comets

Wekhof, A.

doi:10.1007/bf00910606

Cited by 20 publications

(13 citation statements)

References 23 publications

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“…This value is five orders of the magnitude smaller than that of the column density of C À 2 ions in comet Scorichenko-George. Theoretical calculations predict for comet Halley a negative ion abundance as low as 10 À6 -10 À10 of the electron densities in the inner coma (Wekhof, 1981). Although such theoretical predictions agree with the experimental results of investigations on comet Halley, they also disagree with those of high C À 2 abundance in comet Scorichenko-George.…”

Section: Possible Detection Of C à 2 and Co In Comet C=2000 Wm1contrasting

confidence: 51%

Spectral Observations of Comet C/2000 Wm1 (Linear) in Mexico

Churyumov

Lukyanyk

Berezhnoy

et al. 2003

Astronomical & Astrophysical Transactions

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Section: Possible Detection Of C à 2 and Co In Comet C=2000 Wm1contrasting

confidence: 51%

Spectral Observations of Comet C/2000 Wm1 (Linear) in Mexico

Churyumov

Lukyanyk

Berezhnoy

et al. 2003

Astronomical & Astrophysical Transactions

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“…Moreover, these observations revealed the presence of electrons, and positive as well as negative ions ðH þ ; H À Þ; ðO þ ; O À Þ; ðSi þ ; Si À Þ; ðOH þ ; OH À Þ, etc. 29 For our present numerical investigation, we have considered ðH þ ; H À Þ and pure ice dust grains. These parameters are 29-33 n þ0 $ 2 Â 10 8 m À3 , n d0 $ 1 m À3 ; T e $ 100 eV; m þ ¼ m À $ 1:6726 Â 10 À27 kg; B 0 $ 7:5 Â 10 À3 T; r d $ 5 lm, and c d $ 5=3.…”

Section: Numerical Resultsmentioning

confidence: 99%

Dust-acoustic shock waves in a charge varying electronegative magnetized dusty plasma with nonthermal ions: Application to Halley Comet plasma

Tribeche

Bacha

2013

Physics of Plasmas

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Weak dust-acoustic waves (DAWs) are addressed in a nonthermal charge varying electronegative magnetized dusty plasmas with application to the Halley Comet. A weakly nonlinear analysis is carried out to derive a Korteweg-de Vries-Burger equation. The positive ion nonthermality, the obliqueness, and magnitude of the magnetic field are found to modify the dispersive and dissipative properties of the DA shock structure. Our results may aid to explain and interpret the nonlinear oscillations that may occur in the Halley Comet Plasma. V C 2013 AIP Publishing LLC.

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“…Finally, the possibility of the formation of negative ions (e.g., OH-, CN-, H-, 02-) in the inner coma due to a number of processes has been considered by Wekhof[1981]. While some of the processes discussed, such as direct electron attachment to abundant species of high electron afiSnity (e.g., OH) in the inner coma, are expected, some of the other processes suggested by the author, such as charge inversion during keV positive ion scattering by cometary dust, are more speculative.…”

Section: (Oh + He-• O + H) An 8 Km S -] Component Is Also Produced Bmentioning

confidence: 99%

“…This corresponds typically to an erosion of about 10 cm of surface and is thus not very much smaller than the amount of erosion between 5 AU and perihelion at about 0.5 AU (for example, see Mendis and Brin [1977]). The source of loose, fine dust on the surface is presumed to be due either to cosmic ray damage while in the Oort cloud [Whipple, 1977] or to the nonconsolidation of the upper layers of dust deposited during cosmogonic times. It is seen that this output of dust from comets beyond 5 AU could provide a substantial new source of fine dust in the outer solar system.…”

Section: Mendis Et Al [1981]mentioning

confidence: 99%

The cometary atmosphere and its interaction with the solar wind

Mendis¹,

Houpis²

1982

Reviews of Geophysics

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The present state of both our knowledge and our understanding of cometary atmospheres and their interactions with the solar wind is critically reviewed. Following the introduction (section 1) the spectrophotometry of the cometary atmosphere and the tail is reviewed in section 2. The existing, rather fragmentary, knowledge about atmospheric abundances and the production rates of various molecular species is given in section 3. The deductions that can be made from these values about the chemical composition of the nucleus and their uncertainties are discussed. Existing models of the cometary atmosphere including the ionosphere are critically evaluated in section 4. The continuing dichotomy between models that concentrate on the chemistry while oversimplifying the dynamics and those that concentrate on the dynamics and thermodynamics while minimizing the chemistry is discussed. The need to combine these two approaches in the future is emphasized. The ionization processes in the cometary atmosphere are discussed in section 5. It is emphasized that besides photoionization and charge exchange ionization with the solar wind protons, other (collisional) ionization processes may play a role in the rapid ionization of cometary neutrals in certain situations. The overall nature of the solar wind‐comet interaction is discussed in section 6 with special emphasis on the strong coupling between the solar wind and cometary plasmas, which is responsible for the observed accelerations in the cometary tails. The complex and time‐varying fine structures observed in the plasma tails of comets are discussed next in section 7. The uses of these to infer the strength and morphology of the magnetic field and the associated currents in the plasma tail on one hand, and the varying conditions in the solar wind on the other, are emphasized. The detailed models of the comet‐solar wind interaction, from the earlier fluid dynamic models to the latest MHD models are critically evaluated in section 8, and their limitations are underscored. It is also pointed out that the nature of the solar wind interaction with the cometary atmosphere is highly variable and that in certain circumstances the nature of both the outer and the inner shocks could change. Also, the need for a detailed study of the solar wind interaction with the fledgling cometary atmosphere at larger heliocentric distances is stressed. The review is concluded with section 9, where the emphasis is on the outstanding problems of cometary atmospheres and their interactions with the solar wind.

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Negative ions in comets

Cited by 20 publications

References 23 publications

Spectral Observations of Comet C/2000 Wm1 (Linear) in Mexico

Spectral Observations of Comet C/2000 Wm1 (Linear) in Mexico

Dust-acoustic shock waves in a charge varying electronegative magnetized dusty plasma with nonthermal ions: Application to Halley Comet plasma

The cometary atmosphere and its interaction with the solar wind

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