Gortsas, Nikolaos and Motschmann, Uwe and Kührt, Ekkehard and Knollenberg, Jörg and Simon, Sven and Boesswetter, Alexander (2009) Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study. Annales Geophysicae, 27 (4), pp. 1555-1572. Copernicus Publications. ISSN 0992-7689.
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Official URL: http://www.ann-geophys.net/27/1555/2009/
The effects of coma anisotropies on the plasma environment of comets have been studied by means of a 3-D hybrid model which treats electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. From Earth-based observations as well as from in-situ spacecraft measurements the shape of the coma of many comets is ascertained to be anisotropic. However, most plasma simulation studies deploy a spherically symmetric activity pattern. In this paper anisotropy is studied by considering three different coma shape models. The first model is derived from the Haser model and is characterised by spherically symmetry. This reference model is then compared with two different neutral gas shape models: the dayside restricted model with no nightside activity and a cone shaped model with opening angle of π/2. In all models the integrated surface activity is kept constant. The simulations have been done for the Rosetta target comet 67P/Churyumov-Gerasimenko for two heliocentric distances, 1.30 AU and 3.25 AU. It is found that shock formation processes are modified as a result of increasing spatial confinement. Characteristic plasma structures of comets such as the bow shock, magnetic barrier region and the ion composition boundary exhibit a shift towards the sun. In addition, the cone shaped model leads to a strong increase of the mass-loaded region which in turn leads to a smooth deceleration of the solar wind flow and an increasing degree of mixture between the solar wind and cometary ion species. This creates an additional transport channel of the magnetic field from the magnetic barrier region away which in turn leads to a broadening of this region. In addition, it leads to an ion composition boundary which is only gradually developed.
|Title:||Mapping of coma anisotropies to plasma structures of weak comets: a 3-D hybrid simulation study|
|Date:||2 April 2009|
|Journal or Publication Title:||Annales Geophysicae|
|In Open Access:||Yes|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 1555-1572|
|Keywords:||Comets, Plasma Simulations, Numerical Simulation Studies, Kometen, Plasmasimulationen, Numerik|
|HGF - Research field:||Aeronautics, Space and Transport (old)|
|HGF - Program:||Space (old)|
|HGF - Program Themes:||W EW - Erforschung des Weltraums|
|DLR - Research area:||Space|
|DLR - Program:||W EW - Erforschung des Weltraums|
|DLR - Research theme (Project):||W - Vorhaben Asteroiden und Kometen (old)|
|Institutes and Institutions:||Institute of Planetary Research > Asteroids and Comets|
|Deposited By:||Nikolaos Gortsas|
|Deposited On:||07 Apr 2009|
|Last Modified:||04 Apr 2013 15:50|
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