Planetary magnetism and the thermal evolution of planetary cores

1981 ◽  
pp. 105-109 ◽  
Author(s):  
David Gubbins
Keyword(s):  
Thermal Evolution ◽  
Planetary Cores ◽  
Planetary Magnetism

scholarly journals Sculpting the valley in the radius distribution of small exoplanets as a by-product of planet formation: the core-powered mass-loss mechanism

2019 ◽  
Vol 487 (1) ◽  
pp. 24-33 ◽  
Author(s):  
Akash Gupta ◽  
Hilke E Schlichting
Keyword(s):  
Mass Loss ◽  
Thermal Evolution ◽  
Relative Magnitude ◽  
Occurrence Rate ◽  
Loss Mechanism ◽  
Water Ice ◽  
The Core ◽  
Planetary Cores ◽  
Short Period ◽  
Atmospheric Mass

ABSTRACT Recent observations revealed a bimodal radius distribution of small, short-period exoplanets with a paucity in their occurrence, a radius ‘valley’, around 1.5–2.0 R⊕. In this work, we investigate the effect of a planet’s own cooling luminosity on its thermal evolution and atmospheric mass loss (core-powered mass-loss) and determine its observational consequences for the radius distribution of small, close-in exoplanets. Using simple analytical descriptions and numerical simulations, we demonstrate that planetary evolution based on the core-powered mass-loss mechanism alone (i.e. without any photoevaporation) can produce the observed valley in the radius distribution. Our results match the valley’s location, shape and slope in planet radius–orbital period parameter space, and the relative magnitudes of the planet occurrence rate above and below the valley. We find that the slope of the valley is, to first order, dictated by the atmospheric mass-loss time-scale at the Bondi radius and given by d logRp/d logP ≃ 1/(3(1 − β)) that evaluates to −0.11 for β ≃ 4, where Mc/M⊕ = (Rc/R⊕)β(ρc∗/ρ⊕)β/3 is the mass–radius relation of the core. This choice for β yields good agreement with observations and attests to the significance of internal compression for massive planetary cores. We further find that the location of the valley scales as $\rho _{\rm c*}^{-4/9}$ and that the observed planet population must have predominantly rocky cores with typical water–ice fractions of less than ${\sim } 20{{\, \rm per\, cent}}$. Furthermore, we show that the relative magnitude of the planet occurrence rate above and below the valley is sensitive to the details of the planet-mass distribution but that the location of the valley is not.

Dynamos in the Inner Solar System

2021 ◽  
Vol 50 (1) ◽  
Author(s):  
Sonia M. Tikoo ◽  
Alexander J. Evans
Keyword(s):  
Solar System ◽  
Magnetic Fields ◽  
Thermal Evolution ◽  
Annual Review ◽  
Publication Date ◽  
The Moon ◽  
Conductive Liquid ◽  
Mechanical Stirring ◽  
Planetary Cores ◽  
Thermochemical Convection

Dynamo magnetic fields are primarily generated by thermochemical convection of electrically conductive liquid metal within planetary cores. Convection can be sustained by secular cooling and may be bolstered by compositional buoyancy associated with core solidification. Additionally, mechanical stirring of core fluids and external perturbations by large impact events, tidal effects, and orbital precession can also contribute to sustaining dynamo fields. Convective dynamos cease when the core-mantle heat flux becomes subadiabatic or if specific crystallization regimes inhibit core fluid flows. Therefore, exploring the histories of magnetic fields across the Solar System provides a window into the thermal and chemical evolution of planetary interiors. Here we review how recent spacecraft-based studies of remanent crustal magnetism, paleomagnetic studies of rock samples, and planetary interior models have revealed the magnetic and evolutionary histories of Mercury, Earth, Mars, the Moon, and several planetesimals, as well as discuss avenues for future exploration and discovery. ▪ Paleomagnetism and remanent crustal magnetism studies elucidate the magnetic histories of rocky planetary bodies. ▪ Records of ancient dynamo fields have been obtained from 3 out of 4 terrestrial planets, the Moon, and several planetesimals. ▪ The geometries, intensities, and longevities of dynamo fields can provide information on core processes and planetary thermal evolution. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

THE THERMAL EVOLUTION OF METAPELITIC GRANULITES FROM JUBRIQUE SEQUENCE (BETIC CORDILLERA, S SPAIN)

2016 ◽  
Author(s):  
Marco Crivellaro ◽  
◽  
Omar Bartoli ◽  
Bernardo Cesare ◽  
Antonio Acosta-Vigil ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Betic Cordillera ◽  
Metapelitic Granulites

THERMAL EVOLUTION OF ULTRAMAFIC BODIES IN THE EASTERN BLUE RIDGE MOUNTAINS, NC

2018 ◽  
Author(s):  
Anna VanDusen ◽  
◽  
Katharine Johanesen ◽  
Kaylee Pennell ◽  
Adam J. Ianno ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Blue Ridge ◽  
Blue Ridge Mountains
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