Abstract Details

Name: Sana Ahmed
Affiliation: Physical Research Laboratory
Conference ID: ASI2020_330
Title : A Multi-fluid Model to Study the Coma of a Comet
Authors and Co-Authors : Sana Ahmed and Kinsuk Acharyya
Abstract Type : Poster
Abstract Category : Sun and the Solar System
Abstract : Comets are icy bodies that reside in the outer regions of the Solar System. Water is the primary volatile present in cometary ice, along with CO, CO2, NH3, and other volatiles. When the comet approaches the Sun, the volatiles sublimate to form the surrounding coma. Generally, water vapour is the dominant component of the coma, especially at smaller heliocentric distances (< 2 AU). At further distances, species such as CO that have higher vapour pressure than water may dominate. In this work, we assume a cometary nucleus made up of assorted primary cometary ices like H2O, CO2, and N2. These primary species sublimate, and undergo photodissociation due to solar UV radiation, resulting in the formation of secondary species. The products of photolytic decomposition also react with each other. All of these species form the coma and expand outward. In the inner regions of the coma (< 10^4 km), the density is high enough to adopt a fluid approach for the gas. A multi-fluid approach is considered, such that the neutral species evolve differently from the atomic hydrogen and the electrons. The equations for the conservation of number density, momentum, and energy are used to describe the evolution of the coma with cometocentric distance. Numerical integration of these equations is done to obtain the radial profile of the temperature, velocity, and number densities of the different species. The evolution of the coma over an entire cometary orbit (varying heliocentric distances) will also be discussed.