New models of Jupiter in the context of Juno and Galileo. (arXiv:1901.05697v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Debras_F/0/1/0/all/0/1">Florian Debras</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chabrier_G/0/1/0/all/0/1">Gilles Chabrier</a>
Observations of Jupiter’s gravity field by Juno have revealed surprisingly
small values for the high order gravitational moments, considering the
abundances of heavy elements measured by Galileo 20 years ago. The derivation
of recent equations of state for hydrogen and helium, much denser in the Mbar
region, worsen the conflict between these two observations. In order to
circumvent this puzzle, current Jupiter model studies either ignore the
constraint from Galileo or invoke an ad hoc modification of the equations of
state. In this paper, we derive Jupiter models which satisfy both Juno and
Galileo constraints. We confirm that Jupiter’s structure must encompass at
least four different regions: an outer convective envelope, a region of
compositional, thus entropy change, an inner convective envelope and an
extended diluted core enriched in heavy elements, and potentially a central
compact core. We show that, in order to reproduce Juno and Galileo
observations, one needs a significant entropy increase between the outer and
inner envelopes and a smaller density than for an isentropic profile,
associated with some external differential rotation. The best way to fulfill
this latter condition is an inward decreasing abundance of heavy elements in
this region. We examine in details the three physical mechanisms able to yield
such a change of entropy and composition: a first order molecular-metallic
hydrogen transition, immiscibility between hydrogen and helium or a region of
layered convection. Given our present knowledge of hydrogen pressure
ionization, combination of the two latter mechanisms seems to be the most
favoured solution.
Observations of Jupiter’s gravity field by Juno have revealed surprisingly
small values for the high order gravitational moments, considering the
abundances of heavy elements measured by Galileo 20 years ago. The derivation
of recent equations of state for hydrogen and helium, much denser in the Mbar
region, worsen the conflict between these two observations. In order to
circumvent this puzzle, current Jupiter model studies either ignore the
constraint from Galileo or invoke an ad hoc modification of the equations of
state. In this paper, we derive Jupiter models which satisfy both Juno and
Galileo constraints. We confirm that Jupiter’s structure must encompass at
least four different regions: an outer convective envelope, a region of
compositional, thus entropy change, an inner convective envelope and an
extended diluted core enriched in heavy elements, and potentially a central
compact core. We show that, in order to reproduce Juno and Galileo
observations, one needs a significant entropy increase between the outer and
inner envelopes and a smaller density than for an isentropic profile,
associated with some external differential rotation. The best way to fulfill
this latter condition is an inward decreasing abundance of heavy elements in
this region. We examine in details the three physical mechanisms able to yield
such a change of entropy and composition: a first order molecular-metallic
hydrogen transition, immiscibility between hydrogen and helium or a region of
layered convection. Given our present knowledge of hydrogen pressure
ionization, combination of the two latter mechanisms seems to be the most
favoured solution.
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