Laboratory simulation of cometary neutral gas ionization

Chang, T.; Rahman, H. U.; White, R. S.

doi:10.1029/ja094ia05p05533

Cited by 7 publications

(2 citation statements)

References 16 publications

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“…The equations for the particles and waves in a homogeneous infinite medium have been solved in the quasi-linear approximation [Galeev, 1981;Formisano et al, 1982;Papadopoulos, 1983Papadopoulos, , 1984 and have been successfully modeled by particle simulation [McBride et al, 1972;Tanaka and Papadopoulos, 1983;Abe and Machida, 1985;Goertz, 1986, 1988;Goertz et al, 1990;McNeil et al, 1990]. Although there are several observations of frequencies in the LH range, both in laboratory [e.g., Eselevich and Fainshtein, 1986;Chang, 1988;Chang et al, 1989] and in ionospheric releases [e.g., Kelley et al, 1986], there are also measurements [Swenson et al, 1990;Nickenig and Piel, 1987] (see also Brenning [1992]) which are at odds with the wave properties seen in analytic solutions and the simulations mentioned above. For example, the wave spectrum obtained in the Bochum I homopolar discharge [Nickenig and Piel, 1987] shows that the LH frequency is absent, and the wave measurements at a distance 1.7 km from the release point in the CRIT II gas release experiment show oscillations far below the LH frequency [Swenson et al, 1990].…”

Section: Nba(x) = Nbaolnc(x) [1 -•T(x)] (2)mentioning

confidence: 99%

Numerical quasi‐linear study of the critical ionization velocity phenomenon

Moghaddam-Taaheri¹,

Goertz²

1993

J. Geophys. Res.

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The critical ionization velocity (CIV) for a neutral barium (Ba) gas cloud moving across the static magnetic field is studied numerically using quasi‐linear equations and a parameter range which is typical for the shaped‐charge Ba gas release experiments in space. For consistency the charge exchange between the background oxygen ions and neutral atoms and its reverse process, as well as the excitation of the neutral Ba atoms, are included. The numerical results indicate that when the ionization rate due to CIV becomes comparable to the charge exchange rate the energy lost to the ionization and excitation collisions by the superthermal electrons exceeds the energy gain from the waves that are excited by the ion beam. This results in a CIV yield less than the yield by the charge exchange process.

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Section: Nba(x) = Nbaolnc(x) [1 -•T(x)] (2)mentioning

confidence: 99%

Numerical quasi‐linear study of the critical ionization velocity phenomenon

Moghaddam-Taaheri¹,

Goertz²

1993

J. Geophys. Res.

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“…Brenning [1985] pointed out that (74) gives a lower limit to B. Figure 19 shows an experimental proof of the lower limit of B for CIV to occur [Chang et al, 1989]. Thus the range of magnetic field B for CIV is occur is limited by B• > B > B2,…”

Section: Velocity Conditionmentioning

confidence: 99%

A review of critical ionization velocity

Lai¹

2001

Reviews of Geophysics

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Abstract. This paper reviews the critical ionization velocity (CIV) phenomenon, with inclusion of recent research. CIV, suggested by Alfv6n in 1954 as part of a larger cosmological theory accounting for the formation of the solar system, is controversial in that laboratory and space experiments to confirm its validity have yielded conflicting results. Theoretical analysis has suggested that the driving mechanism for CIV is some form of beam-plasma instability, such as the lower hybrid instability, which leads to rapid energization of ambient electrons so that they gain enough energy to ionize the beam of neutral atoms by electron impact. The newly created beam ions energize the instability, thus fostering a cyclic process that may lead to an avalanche ionization. Because which the laboratory and the space experiments are carried out and highlight the differences, some of which may explain the different results. INTRODUCTIONThe concept of critical ionization velocity (CIV) [Alfv•n, 1954[Alfv•n, , 1960] is deceptively simple: When a neutral gas travels through a magnetized plasma with a relative velocity exceeding a critical value, rapid ionization of the neutral gas occurs (Figure 1). The critical value of the relative velocity is. given by Vc = x/2e q) /M,where e q) is the ionization energy of a neutral particle and M is its mass. Several reviews of this theory and experimental tests have appeared [Sherman, 1973;Danielsson, 1973;Newell, 1985;Torbert, 1988Torbert, , 1990, the most recent and the most thorough being that by Brenning [1992]. Our aim in this review is to present a more thorough review, giving the pertinent information about the work in the field without going into more detail than necessary. Figure 2 shows, the critical velocities of elements group into bands. As the neutral atoms ionized, they were trapped by the magnetic field, where they underwent collisions to form clusters and other complex ionic species, which were eventually neutralized. Thus, according to Alfv6n, it was this process of condensation and subsequent neutralization that led to the formation of the planets. Since the critical velocities Vc of the elements fall roughly into several bands, several planets were formed, each with a different chemical composition. As will be discussed in the nextRecently, the line widths of the HI (neutral hydrogen emission) lines in interstellar filaments have been oh-

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Review of the CIV phenomenon

Brenning

1992

Space Sci Rev

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Laboratory simulation of cometary neutral gas ionization

Cited by 7 publications

References 16 publications

Numerical quasi‐linear study of the critical ionization velocity phenomenon

Numerical quasi‐linear study of the critical ionization velocity phenomenon

A review of critical ionization velocity

Review of the CIV phenomenon

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