  The effect of micron-sized particles on a low-pressure capacitively-coupled
rf discharge is studied both experimentally and using numerical simulations. In
the laboratory experiments, microparticle clouds occupying a considerable
fraction of the discharge volume are supported against gravity with the help of
the thermophoretic force. The spatiotemporally resolved optical emission
measurements are performed with different arrangements of microparticles. The
numerical simulations are carried out on the basis of a one-dimensional hybrid
(fluid-kinetic) discharge model describing the interaction between plasma and
microparticles in a self-consistent way. The study is focused on the role of
microparticle arrangement in interpreting the spatiotemporal emission
measurements. We show that it is not possible to reproduce simultaneously the
observed microparticle arrangement and emission pattern in the framework of the
considered one-dimensional model. This disagreement is discussed and attributed
to two-dimensional effects, e.g., radial diffusion of the plasma components.
