Colloquium: Dr. Ludmilla Kolokolova, UMD, College Park

Natural dust particles often are aggregates (agglomerates), i.e. they represent a cluster of small constituent grains. Besides the familiar house dust, aggregates are also some terrestrial aerosols (e.g., sooth and icy particles) and almost all particles of extraterrestrial origin (interplanetary and cometary dust, aerosols in Titan and Martian atmospheres, dust in circumstellar disks and star-forming regions). Particles of aggregated structure are also typical for biogenic and man-made hydrosols and aerosols. Characterization of these particles, i.e. revealing their composition, size, and structure allows us not only to better describe them but also to understand their formation and evolution. Astronomy, as a science that is almost completely based on remote-sensing information, has developed numerous techniques for simulation of light scattering by such particles to remotely study their characteristics. A very powerful  modeling technique is the T-matrix approach, originally called “extended boundary conditions” technique that represents a solution of the Maxwell equations, thus, providing a rigorous and physically correct description of light scattering by particles of different shape and structure. I will describe capabilities of the T-matrix codes of different complexity and show what information about aggregates we could reveal using the T-matrix approach. Special attention will be given to polarimetric properties of aggregated particles and to application of the T-matrix techniques to cosmic dust particles and aggregates of biological origin.

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