SHOCK WAVES IN COLLISION-FREE PLASMAS

Technical Report · Tue Aug 01 04:00:00 EDT 1961

OSTI ID:4836327

Camac, M; Kantrowitz, A R; Litvak, M M; Patrick, R M; Petschek, H E

Investigations of shock-wave structures provide an excellent opportunity for studying the dissipation processes in collision-free plasntas. The thickness of collision-free shock waves was previously obtained from measurements of the light emitted by the plasma in a magnetic annular shock tube. The magnitude of the shock thickness, and its Mach number and density dependence were in agreement with a theoretical estimate based on the concept that the required dissipation in the shock is produced by non-linear interactions between-magnetohydrodynamic waves. Measurements of the magnetic field have shown that the magnitude of the field change across the shock agrees with that expected from the conservation equations. Also the distance over which the field changes agrees with the previous shock thickness measurements. The electron temperature was estimated to be above 10 ev based on the ultraviolet radiation intensity and the ratio of bound-bound and free-free radiation. Measurements of the heat transfer from the plasma to the shock-tube wall indicate that less than 1/10 of the gas energy is dissipated to the walls, thus, there is good containment of the shock heated plasma for a time large compared to the shock rise transit time. The theory of the wave dissipation mechanism has been reformulated so that the distribution of wave action in wave-vector space is described by a Boltzmann equation similar to that for the distribution of phonons in solids. Estimates of relaxation times for the non-linear wave interactions agree with previous predictions. Preliminary results for the shock structure suggest that in the shock front the wave distribution is somewhat concentrated in regions of wave-vector space away from the origin. There are indications that the wave frequency band should be narrow at the shock front and increase going toward the back of the shock. Waves of about ion-cyclotron frequency may persist behind the shock while other waves spread to high frequencies by wave-wave collisions and are damped. (auth)

• Research Organization: Avco Corp. Avco-Everett Research Labs., Everett, Mass.
• NSA Number: NSA-16-001104
• OSTI ID: 4836327
• Report Number(s): AFOSR-1173
• Country of Publication: United States
• Language: English

Related Subjects

ALFVEN WAVES
BOLTZMANN EQUATION
COLLISIONLESS PLASMA
CONFINEMENT
CONSERVATION LAWS
CYCLOTRON FREQUENCY
CYCLOTRON RADIATION
DAMPING
DENSITY
DIFFERENTIAL EQUATIONS
DISTRIBUTION
EMISSION
EV RANGE
FREQUENCY
HEAT TRANSFER
HYDROMAGNETIC WAVES
INTERACTIONS
IONS
LIGHT
MACH NUMBER
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICS
NONLINEAR PROBLEMS
OSCILLATIONS
PHYSICS
PLASMA
PLASMA WAVES
RELAXATION
RESONANCE
SHOCK WAVES
SURFACES
TEMPERATURE
THICKNESS
TORUS
TRANSPORT THEORY
TUBES
ULTRAVIOLET RADIATION
VARIATIONS
VELOCITY
VESSELS