On the possibility to determine the electrical conductivity of 67P/CG from ROSETTA magnetic field observations

The ROSETTA mission to comet 67P/Churyumov-Gerasimenko presents us for the first time the opportunity to study the interior of a cometary nucleus. Information about the electrical conductivity and its distribution inside the nucleus can be derived by measuring the magnetic fields induced in the nucleus by variations of the interplanetary magnetic field. Due to the relatively small size of the nucleus, this task is not trivial and requires very precise magnetic field measurements. e analyze the response of a conductive nucleus to transient step-like magnetic field changes as well as the response in frequency domain to electromagnetic waves. For the nucleus we use a spherical model with either uniform conductivity or consisting of a core and an outer layer with different conductivities. The space outside of the nucleus is modeled either by highly conductive solar wind plasma or by zero conductivity void. s combinations of conductivities, radii of the nucleus and of the core, and properties of the space outside the nucleus result in different inductive responses. Several such combinations which could be encountered by ROSETTA are studied in detail in order to estimate which conductivity ranges and core radii can be determined using the ROSETTA instruments and which mission operations would facilitate such measurements.