Other
Scientific paper
Sep 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.4008t&link_type=abstract
American Astronomical Society, DPS meeting #41, #40.08
Other
Scientific paper
Magnetic field of Super-Earths is one of important key-factors for a planet to be habitable. Because Earth is shielded by the strong and stable magnetic field from the solar wind that is hazardous for the life. The magnetic field also plays an important role to prevent atmospheric escape. Magnetic field of terrestrial planet is thought to be generated by the dynamo action within its metallic core. The action also requires vigorous convection of the metallic core, and whether the convection occurs or not depends on the thermal transfer efficiency of the mantle. Thus, the generation of magnetic field of Super-Earths is highly related to its internal thermal evolution.
Based on this standpoint, we conducted a series of numerical simulations on thermal evolution of super-Earths of which mass are 1 to 10 Earth mass and examined how long their magnetic field is sustained based on the results of the simulations. In our model, 1 dimensional density structure of planetary interior is calculated taking into account the compressibility of rock and metal by using Birch-Murnaghan equation of state. The thermal transfer through the rocky mantle is calculated by using mixing length theory modified for the mantle convection taking into account the temperature- and pressure-dependency of mantle viscosity.
According to our numerical results, if we assumed that the initial temperature of core surface is sufficiently high, the life-time of magnetic field is monotonically increased with planetary mass and thermal evolution is independent of initial conditions. On the other hand, if we adopt the same initial conditions for planets with different mass, the life-time of planetary magnetic field have the maximum value at some mass.
These results are due to strong temperature- and pressure-dependency of mantle viscosity.
Ida Shigeru
Senshu Hiroki
Tachinami Chihiro
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