Thermal state and gas production rate of rotating cometary nuclei

We formulate a completely three-dimensional nonstationary model of the thermal state and gas production rate of rotating spherical cometary nuclei moving in circular and elliptical orbits around the Sun. We perform a thermophysical analysis of the problem and formulate a system of similarity criteria. The possible thermal regimes of cometary nuclei are analyzed in the space of suggested similarity criteria. Only one criterion dependent on the nucleus spin period is shown to play a dominant role for rotating nuclei at a given heliocentric distance. This simplifies greatly a parametric study of the gas production rate of real cometary nuclei under conditions of uncertainty in their parameters. Based on the developed model, we numerically investigate the thermal state and gas production rate of rotating nuclei. The results of our calculations are in complete agreement with those of the similarity analysis for the problem. We perform a comparative analysis of the currently used simplified thermal models for cometary nuclei and determine the range of their applicability.