THE INFLUENCE OF MAGNETIC FIELD GEOMETRY ON THE FORMATION OF CLOSE-IN EXOPLANETS

Journal Article · Sat Aug 20 00:00:00 EDT 2016 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8205/827/2/L37· OSTI ID:22654240

Simon, Jacob B., E-mail: [e-mail] ^[1]

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1. Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States)

Approximately half of Sun-like stars harbor exoplanets packed within a radius of ∼0.3 au, but the formation of these planets and why they form in only half of known systems are still not well understood. We employ a one-dimensional steady-state model to gain physical insight into the origin of these close-in exoplanets. We use Shakura and Sunyaev α values extracted from recent numerical simulations of protoplanetary disk accretion processes in which the magnitude of α , and thus the steady-state gas surface density, depend on the orientation of large-scale magnetic fields with respect to the disk’s rotation axis. Solving for the metallicity as a function of radius, we find that for fields anti-aligned with the rotation axis, the inner regions of our model disk often fall within a region of parameter space that is not suitable for planetesimal formation, whereas in the aligned case, the inner disk regions are likely to produce planetesimals through some combination of streaming instability and gravitational collapse, though the degree to which this is true depends on the assumed parameters of our model. More robustly, the aligned field case always produces higher concentrations of solids at small radii compared to the anti-aligned case. In the in situ formation model, this bimodal distribution of solid enhancement leads directly to the observed dichotomy in exoplanet orbital distances.

• OSTI ID: 22654240
• Journal Information: Astrophysical Journal Letters, Vol. 827, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ACCRETION DISKS
APPROXIMATIONS
COMPUTERIZED SIMULATION
CONCENTRATION RATIO
DENSITY
DISTRIBUTION
GRAVITATIONAL COLLAPSE
INSTABILITY
MAGNETIC FIELDS
METALLICITY
ONE-DIMENSIONAL CALCULATIONS
PLANETS
PROTOPLANETS
ROTATION
SATELLITES
SPACE
STEADY-STATE CONDITIONS
SUN
SURFACES