An overview of atomic and molecular processes in critical velocity ionization

Journal Article · Sat Apr 01 04:00:00 EST 1989 · IEEE Trans. Plasma Sci.; (United States)

DOI:https://doi.org/10.1109/27.24617· OSTI ID:6058681

Lai, S T; Murad, E; McNeil, W J

Alfven's critical ionization velocity (CIV) is a multistep process involving plasma physics and plasma chemistry. The authors present an overview of the time development of some atomic and molecular processes in CIV. In the pre-onset stage, metastable states play an important role: They provide an energy pooling mechanism allowing low energy electrons to participate in the ionization processes; they may explain the low energy threshold as well as the fast time scale in the onset of CIV. For a sustaining CIV to occur, Townsend's criterion has to be satisfied. The kinetic energies of the neutrals are transformed to plasma wave energies via beam-plasma instabilities, and the plasma waves that heat the electrons result in a tail formation. Excitation of neutrals with subsequent radiation is an important energy loss mechanism. Finite beam size also limits the instability growth rate. In the propagation of CIV, ion-molecule reactions and molecular dissociative recombination are important. Ion-molecule reactions change the temporal chemical composition in a CIV process and help explain some results in CIV experiments. Molecular dissociative recombination reduces the plasma density, lowers the effective neutral mass, and loses energy via excitation and radiation; it tends to quench the propagation of CIV. Depending on various parameters, oscillatory behavior of CIV may occur.

• Research Organization: Air Force Geophysics Lab., Hanscom Air Force Base, Bedford, MA (US); Radex, Inc., Bedford, MA (US)
• OSTI ID: 6058681
• Journal Information: IEEE Trans. Plasma Sci.; (United States), Journal Name: IEEE Trans. Plasma Sci.; (United States) Vol. 17:2; ISSN ITPSB
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700103 -- Fusion Energy-- Plasma Research-- Kinetics
700107* -- Fusion Energy-- Plasma Research-- Instabilities
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
ALFVEN WAVES
ATOMS
COLLISIONS
CRITICAL VELOCITY
DATA
DOCUMENT TYPES
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
ENERGY LEVELS
ENERGY LOSSES
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
EXPERIMENTAL DATA
FERMIONS
HYDROMAGNETIC WAVES
INFORMATION
INSTABILITY
ION COLLISIONS
ION-MOLECULE COLLISIONS
IONIZATION
KINETIC ENERGY
LEPTONS
LOSSES
METASTABLE STATES
MOLECULE COLLISIONS
MOLECULES
NUMERICAL DATA
PHYSICS
PLASMA
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA WAVES
RECOMBINATION
REVIEWS
VELOCITY
WAVE PROPAGATION