Behaviors of positively charged fine particles in a cross field sheath   between magnetized double plasmas
  Dependencies of levitation position of positively charged fine-particles on plasma parameters are investigated. The charges on the particles become positive in a cross-field sheath between magnetized double plasmas with different potentials separated vertically by horizontal magnetic field, because ion current flowing from a lower high-potential plasma surpasses electron current coming across the magnetic field from an upper low-potential plasma.   From measurement of the resonance frequency of the particles driven by external oscillating electric field, the charge on particle is estimated to be of the order of 10e2. Variation of particle levitation positions can be explained by the change of the charges. 
Takuma Gohda, Satoru Iizuka