Bastian Gundlach, Jürgen Blum
In this work, we present a new model for the heat conductivity of porous dust
layers in vacuum, based on an existing solution of the heat transfer equation
of single spheres in contact. This model is capable to distinguish between two
different types of dust layers: dust layers composed of single particles
(simple model) and dust layers consisting of individual aggregates (complex
model). Additionally, we describe laboratory experiments, which were used to
measure the heat conductivity of porous dust layers, in order to test the
model. We found that the model predictions are in an excellent agreement with
the experimental results. Furthermore, the implications of this new model on
the modeling of cometary activity are discussed. Finally, the two variants of
the model are used to calculate the H2O ice outgassing rate of comets as a
function of the thickness of the ice-free dust layer. Therewith, the pressure
inside the dust layer is derived and compared with the tensile strength of the
material in order to distinguish if dust particles can be released by gas drag.
The gas pressure is only capable to release dust particles at ~1AU, if the dust
layers are composed of individual dust aggregates (complex model). At larger
heliocentric distances, more volatile species are necessary to release dust
particles due to sublimation.
View original:
http://arxiv.org/abs/1111.0535
No comments:
Post a Comment