C. C. Venturini and R. H. Comfort
Center for Space Plasma and Aeronomic Research
University of Alabama in Huntsville, Huntsville, AL
Dust particles are known to permeate essentially all regions of space and significantly affect the plasma and radiative environment. The dust particles in the interplanetary medium, produced by a variety of sources, are in a diverse size range, with 5-100 micron particles contributing most to the zodiacal light and infrared radiative background. These particles are charged as a result of their interaction with the solar plasma and ultraviolet radiation. The presence of charged dust grains in a plasma (dusty plasma) provide a charge synch and affect the charge and number density. A experimental technique being developed in the laboratory at Marshall Spaced Flight Center will be presented. The goal of the experiment is two fold: (1) to measurere the scattering and extinction cross sections of some commonly known interplanetary and circumsolar dust particles, and (2) to study the charging mechanisms of individual dust grains as a function of size and incident electron energy. This technique is based on suspending a single charged dust particle in an electrodynamic balance, also known as a quadrupole or Pauli trap. For the infrared extinction cross section measurements, scattered infrared radiation off the particle is measured as a function of angle. Comparison with Mie theory calculations leads to simultaneous determination of the particle radius, the complex refractive index, and the scattering and extinction cross sections. The charging mechnism measurements at present are confined to measurering the particle charge in response to known energy and flux of electrons. The electrodynamic balance tecnique measures the q/m directly. Size and mass of the particle is determined by a 'spring point' measurement, a combination of drag and particle inertial response to electric field oscilations. The combination of the q/m and spring point measurements enables the absolute determination of the number of charges on a single dust grain at all times. An application of this technique will also be discussed for investigation of rotational bursting phenomena whereby large size cosmic and interplanetary particles are believed to fragment into smaller dust particles.