Self-Sustained Levitation of Dust Aggregate Ensembles by Temperature-Gradient-Induced Overpressures

Abstract

In laboratory experiments we observe dust aggregates from 100 mum to 1 cm in size composed of micrometer-sized grains levitating over a hot surface. Depending on the dust sample aggregates start to levitate at a temperature of 400 K. Levitation of dust aggregates is restricted to a pressure range between 1-40 mbar. The levitating is caused by a Knudsen compressor effect. Based on thermal transpiration through the dust aggregates the pressure increases between surface and aggregates. Dust aggregates are typically balanced approximately 100 microm over the surface. On a slightly concave surface individual aggregates are trapped at the center. Ensembles of aggregates are confined in a 2D plane. Aggregates are subject to systematic and random translational and rotational motion. The levitated aggregates are well suited to study photophoretic or thermophoretic forces or the mutual interaction between dust aggregates.