Forming macroscopic solid bodies in circumstellar discs requires local dust concentration levels significantly higher than the mean. Interactions of the dust particles with the gas must serve to augment local particle densities, and facilitate growth past barriers in the metre size range. Amongst a number of mechanisms that can amplify the local density of solids, aerodynamic streaming instability (SI) is one of the most promising. This work tests the physical assumptions of models that lead to SI in protoplanetary disks (PPDs). We conduct laboratory experiments in which we track the three-dimensional motion of spherical solid particles fluidized in a low-pressure, laminar, incompressible, gas stream. The particle sizes span the Stokes-Epstein drag regime transition and the overall dust-to-gas mass density ratio is close to unity. Lambrechts et al. (2016) established the similarity of the laboratory flow to a simplified PPD model flow. We obtain experimental results suggesting an instability due to particle-gas interaction: i) there exist variations in particle concentration in the direction of the mean drag forces; ii) the particles have a tendency to 'catch up' to one another when they are in proximity; iii) particle clumping occurs on very small scales, which implies local enhancements above the background dust-to-gas mass density ratio by factors of several tens; v) the presence of these density enhancements occurs for a mean dust-to-gas mass density ratio approaching or greater than 1; v) we find evidence for collective particle drag reduction when the local particle number density becomes high and when the background gas pressure is high so that the drag is in the continuum regime. The experiments presented here are precedent-setting for observing SI under controlled conditions and may lead to a deeper understanding of how it operates in nature.
Azimuthal Dust Polarization from Aerodynamically Aligned Grains as Evidence for the Streaming Instability in Protoplanetary Disks
National Radio Astronomy Observatory（国家射电天文台）；Iowa State University（爱荷华州立大学）；University of Virginia（弗吉尼亚大学）；New Mexico State University（新墨西哥州立大学）；Institut de Ciències de l’Espai (ICE), CSIC（空间科学研究所（ICE），西班牙高等科学研究委员会）；Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET（阿根廷射电天文研究所）；UNLP（拉普拉塔国立大学天文与地球物理科学学院）；CICPBA)（莱斯大学）；Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata；Rice University
Dust-gas dynamics driven by the streaming instability with various pressure gradients
Department of Physics and Astronomy, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校物理与天文系）；Nevada Center for Astrophysics, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校内华达天体物理学中心）
The effect of dust on vortices II: Streaming instabilities
Laboratoire Lagrange, Observatoire de la Côte d’Azur, Université de la Côte d’Azur（拉格朗日实验室，蔚蓝海岸天文台，蔚蓝海岸大学）；DAMTP, University of Cambridge（剑桥大学应用数学与理论物理系）
Dust back-reaction on gas around planets modifies the cold thermal torque
Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文研究所）；IRAP, Université de Toulouse, CNRS, UPS（图卢兹大学空间物理研究所）；Max-Planck-Institut für Sonnensystemforschung（马克斯·普朗克太阳系研究所）；Division of Space Research & Planetary Sciences, Physics Institute, University of Bern（伯尔尼大学物理学院空间研究与行星科学系）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Fakultät für Physik, Universität Duisburg-Essen（杜伊斯堡-埃森大学物理学院）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Charles University, Faculty of Mathematics and Physics, Astronomical Institute（查理大学数学与物理学院天文研究所）
