FRACTAL AGGREGATES IN SPACE

摘要

Individual cosmic dust particles come in very complex shapes but there are a variety of environments where dust particles are aggregates of smaller grains. These aggregates often can be characterized by a fractal particle structure. Within this fractal framework, morphologically averaged particle properties depend only on a few parameters. Despite the complexity of the individual particles, fractal dimension, aggregate size, and building-block size are sufficient parameters for many applications. This paper reviews the process of aggregation to generate fractal aggregates with focus on some general features of those aggregates (mass to surface ratios, aspect ratios). Some implications for aerodynamical and optical properties (gas- grain coupling times, polarization, extinction) are discussed.