HR: 14:00h
AN: SH43B-02 INVITED     [Abstracts]
TI: Laboratory Experiments on Charging of Individual Dust Grains
AU: * Abbas, M M
EM: Mian.M.Abbas@nasa.gov
AF: NASA-Marshall Space Flight Center, Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35805
AU: Craven, P D
EM: Paul.D.Craven@nasa.gov
AF: NASA-Marshall Space Flight Center, Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35805
AU: Spann, J F
EM: James.F.Spann@nasa.gov
AF: NASA-Marshall Space Flight Center, Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35805
AU: Tankosic, D
EM: tankosd@email.uah.edu
AF: University of Alabama in Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35899
AU: LeClair, A
EM: Andre.Leclair@msfc.nasa.gov
AF: University of Alabama in Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35899
AU: West, E A
EM: Edward.A.West@nasa.gov
AF: NASA-Marshall Space Flight Center, Huntsville, NSSTC-320 Sparkman Dr., Huntsville, AL 35805
AB: Dust particles in astrophysical and space environments are charged by a variety of mechanisms generally involving collisions with electron and ions, and from photoelectric emissions by interaction with incident UV radiation. The sign and the magnitude of the particle charge are determined by the net balance at equilibrium between the charging processes by UV radiation and collisions with charged particles. Knowledge of the charging processes, particle charge and equilibrium potential is important for understanding of a number of physical processes. The charge of a dust grain is a basic parameter that influences the physics of dusty plasmas, and physical and dynamical processes in the planetary, interplanetary and interstellar environments. A fundamental quantity in the charging of dust grains by the photoemission process is the photoelectric yield of the dust grains. Most of the currently available experimental data on photoemissions are based on bulk materials with very little on individual dust grains. It is, however, recognized that the photoelectric yields of micron size grains are different from those based on bulk materials. After a brief review of the currently available measurements, we will present the results of some recent experiments on charging of dust grains carried out on levitated micron size grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were conducted by exposing dust grains of radii in the 0.1 to 5 mm range, to low energy electron beams and UV radiation at 120 to 160 nm wavelengths. In particular, we will present experimentally determined photoelectric efficiencies and yields of individual micron size dust grains of Silica, Olivine, lunar simulants prepared by NASA-JSC, and the lunar sample dust grains retuned by the Luna 24 mission. Comparisons with the available measurements on bulk materials will be made.
DE: 6213 Dust
DE: 6225 Mars
DE: 6250 Moon (1221)
DE: 2100 INTERPLANETARY PHYSICS
DE: 2129 Interplanetary dust
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting