J/A+A/661/A101 Magnetic moments of rocky planets (Rodriguez-Mozos+, 2022)
Internal structures and magnetic moments of rocky planets.
Application to the first exoplanets discovered by TESS.
Rodriguez-Mozos J.M., Moya A.
<Astron. Astrophys., 661, A101 (2022)>
=2022A&A...661A.101R 2022A&A...661A.101R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Magnetic fields
Keywords: planets and satellites: fundamental parameters -
planets and satellites: interiors -
planets and satellites: magnetic fields -
planets and satellites: terrestrial planets
Abstract:
For a planet to be considered habitable on its surface, it is an
important advantage for it to have a magnetic field that protects its
atmosphere from stellar winds as well as cosmic rays. The magnetic
protection of potentially habitable planets plays a key role in
determining the chances of detecting atmospheric biosignatures. In
making an estimate of a planet's magnetic field, its internal
structure must first be known.
This study proposes to use the Preliminary Reference Earth Model
(PREM) internal structure as the base of a numerical model, as it is
considered the best available option for estimating the internal
structure of rocky exoplanets. With this model, we estimate the
magnetic properties of dry and water-rich Earth-like and
Super-Earth-like planets and we apply it to the first 176 planets of
this kind confirmed by the Transiting Exoplanet Survey Satellite
exoplanet mission (TESS).
Using PREM as a reference, we estimated the internal structure of dry
and water-rich rocky planets. This model provides an estimation of the
average density and core size of the planet, which are the key
ingredients for estimating its magnetic moment, depending on whether
it is tidally locked or not. Our model estimates the thermodynamic
variables as a function of pressure and including saltwater as a
component of water-rich exoplanets. In addition, we did not use the
perfect layer differentiation approximation. We validated our model
based on the selection of planets and satellites in the Solar System
with similar characteristics.
Using our model, we estimated the internal structure and magnetic
moment of selected dry and water-rich rocky planets and satellites in
the Solar system. The differences with the observed values in the
internal structure characteristics, mass, average density, moment of
inertia factor, and local Rossby number are remarkably low or even
negligible. The estimated magnetic moments are also very similar to
the observed ones. We applied the model to the first dry and
water-rich rocky planets confirmed by TESS, 176 in total, and we find,
from an astrobiological perspective, that TOI-700 d and TOI-2257 b are
the most interesting examples, as they are located in the habitable
zone. However, we note that their magnetic moments are only about 0.01
of the Earth's magnetic moment.
Description:
We determine an internal structure model for rocky planets. We propose
three reference models: Earth's internal structure defined by PREM
to be used for medium-high density dry rocky exoplanets; Mars assuming
an Earth-like mantle composition for low-density dry rocky exoplanets;
and Ganymede for water-rich rocky exoplanets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb3.dat 143 25 Results for dry rocky planets observed by TESS
after 30,000 runs (Monte Carlo method)
tableb4.dat 143 41 Results for water-rich rocky planets observed by
TESS after 30,000 runs (Monte Carlo method)
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Byte-by-byte Description of file: tableb3.dat tableb4.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Exoplanet designation
13- 18 F6.3 Mgeo Mp Planetary mass normalized to the Earth mass
20- 24 F5.3 Mgeo e_Mp Planetary mass normalized to the Earth mass error
25 A1 --- n_Mp [*] Note on Mp (1)
27- 31 F5.3 Rgeo Rp Planetary radius normalized to the Earth radius
33- 37 F5.3 Rgeo e_Rp Planetary radius normalized to the Earth radius
error
39- 41 A3 --- S:O Spin:Orbit resonance
43- 48 F6.3 d Prot Planetary rotational period (2)
50- 54 F5.3 au a Semi-major axis
56- 60 F5.3 au D2 Inner boundary of the HZ
62- 66 F5.3 au D3 Outer boundary of the HZ
68- 74 F7.2 --- Seff Normalized mean effective flux considering
orbital eccentricity
76- 79 F4.2 d Prob [0/1] Probability of being rocky planet
81- 84 F4.2 --- CMF Core mass fraction
86- 90 F5.3 --- e_CMF Core mass fraction error
92- 95 F4.2 --- MMF Mantle mass fraction
97-101 F5.3 --- e_MMF Mantle mass fraction error
103-106 F4.2 --- IMF ? Ice mass fraction (only in tableb4.dat)
108-111 F4.2 --- e_IMF ? Ice mass fraction error (only in tableb4.dat)
113-117 F5.2 --- Rol local Rossby number
119-123 F5.3 --- e_Rol local Rossby number error
125-131 A7 --- Regime Regime (Dipolar or Multiple)
133-137 F5.2 Earth M Magnetic moment (in Earth magnetic moment unit)
139-143 F5.3 Earth e_M Magnetic moment error
(in Earth magnetic moment unit)
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Note (1): * for Mp estimated following (Chen & Kipping, 2017ApJ...834...17C 2017ApJ...834...17C,
Cat. J/ApJ/834/17)
Note (2): All the planets are tidally locked. Errors in the rotational period
have not been included because they are so small that they have no impact on
the magnetic properties of exoplanets.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Aug-2022