Soutenance d’HDR de Vladimir ZAKHAROV

Titre de la soutenance

"Mathematical simulation of a dusty-gas atmosphere of a comet"

Abstract

Comets are thought to be icy leftovers from planet formation, either planetesimals themselves or direct descendants of the former. These small bodies have undergone very few global changes since their formation in the proto-planetary disc. For that reason, they are widely considered to have retained information about the early Solar System and can inform our understanding of planet formation.

In the absence of a direct exploration of the nucleus, the observations of cometary atmosphere allow us to deduce parameters of the nucleus – its composition, structure etc. and, in this way, to get information about the Solar System formation. The computational models of the nucleus and circumnuclear environment are indispensable tools of that analysis.

In this habilitation thesis, I summarize 20 years of my experience in mathematical simulations of cometary atmospheres. My research domain lies in intersection of astrophysics and computational fluid dynamics. The main goal of my research is to develop a numerical model of dusty gas environment of a comet. Such kind of a model is used for analysis of the data obtained in the accomplished missions (e.g. Rosetta) and for preparation of the future missions (e.g. Comet Interceptor) – to which I also participate. At the same time, it is convenient to address the analysis of complex physical phenomena in a step-bystep manner. Therefore, in addition, I consider a series of simple “pedagogic” cases which results are more spectacular and easier to understand.

Further development of the model will proceed towards increasing the number of processes included into consideration and increasing the physical realism of the model and its components. Though some of the processes might be not important for the general dynamics of the coma they should be included in to consideration due to their importance for interpretation of the observational data. This will allow to extend volume of observational data for interpretation and obtain more detailed information on the processes in the coma and interior of the nucleus.