Radar backscattering from a large-grain cometary coma: numerical simulation

¹ Department of Electrical Engineering, Paderborn University, Warburger Str. 100, 33098 Paderborn, Germany
e-mail: yevgen.grynko@upb.de
² Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019, USA
³ School of Natural Sciences, Far Eastern Federal University, 8 Sukhanova Street, 690950 Vladivostok, Russia

Received: 17 March 2017
Accepted: 12 October 2017

Abstract

We numerically simulate the circular polarization ratio of the radar signal backscattered from a large-grain cometary coma and compare the simulation results with the radar measurements for seven comets. We apply the discrete dipole approximation method and a model of random irregular particles. Our results confirm water ice composition of the cm-sized chunks detected by the NASA Deep Impact space probe in the vicinity of the nucleus of Comet 103P/Hartley 2. The index of the power-law size distribution in this case can be constrained to the range n ≈ 3.3–4.3. For the other considered comets the circular polarization ratio can be reproduced with variations of the power index between 2 and 5.