232 research outputs found
Electromagnetic induction heating as a driver of volcanic activity on massive rocky planets
Aims. We investigate possible driving mechanisms of volcanic activity on
rocky super-Earths with masses exceeding 3-4 Mearth. Due to high gravity and
pressures in the mantles of these planets, melting in deep mantle layers can be
suppressed, even if the energy releae due to tidal heating and radioactive
decay is substantial. Here we investigate whether a newly identified heating
mechanism, namely induction heating by the star's magnetic field, can drive
volcanic activity on these planets due to its unique heating pattern in the
very upper part of the mantle. In this region the pressure is not yet high
enough to preclude the melt formation. Methods. Using the super-Earth HD 3167b
as an example, we calculate induction heating in the planet's interiors
assuming an electrical conductivity profile typical of a hot rocky planet and a
moderate stellar magnetic field typical of an old inactive star. Then we use a
mantle convection code (CHIC) to simulate the evolution of volcanic outgassing
with time. Results. We show that although in most cases volcanic outgassing on
HD 3167b is not very significant in the absence of induction heating, including
this heating mechanism changes the picture and leads to a substantial increase
in the outgassing from the planet's mantle. This result shows that induction
heating combined with a high surface temperature is capable of driving
volcanism on massive super-Earths, which has important observational
implications.Comment: Five pages, three figures, accepted for publication in A&A letter
The Upper Atmospheres of Terrestrial Planets: Carbon Dioxide Cooling and the Earth's Thermospheric Evolution
Context: The thermal and chemical structures of the upper atmospheres of
planets crucially influence losses to space and must be understood to constrain
the effects of losses on atmospheric evolution.
Aims: We develop a 1D first-principles hydrodynamic atmosphere model that
calculates atmospheric thermal and chemical structures for arbitrary planetary
parameters, chemical compositions, and stellar inputs. We apply the model to
study the reaction of the Earth's upper atmosphere to large changes in the
CO abundance and to changes in the input solar XUV field due to the Sun's
activity evolution from 3~Gyr in the past to 2.5~Gyr in the future.
Methods: For the thermal atmosphere structure, we consider heating from the
absorption of stellar X-ray, UV, and IR radiation, heating from exothermic
chemical reactions, electron heating from collisions with non-thermal
photoelectrons, Joule heating, cooling from IR emission by several species,
thermal conduction, and energy exchanges between the neutral, ion, and electron
gases. For the chemical structure, we consider 500 chemical reactions,
including 56 photoreactions, eddy and molecular diffusion, and advection. In
addition, we calculate the atmospheric structure by solving the hydrodynamic
equations. To solve the equations in our model, we develop the Kompot code and
provide detailed descriptions of the numerical methods used in the appendices.
Results: We verify our model by calculating the structures of the upper
atmospheres of the modern Earth and Venus. By varying the CO abundances at
the lower boundary (65~km) of our Earth model, we show that the atmospheric
thermal structure is significantly altered. [Abstract Truncated]Comment: 37 pages, 14 figures, to be published in A&
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