956 research outputs found
Ocean Dynamics and the Inner Edge of the Habitable Zone for Tidally Locked Terrestrial Planets
Recent studies have shown that ocean dynamics can have a significant warming
effect on the permanent night sides of 1 to 1 tidally locked terrestrial
exoplanets with Earth-like atmospheres and oceans in the middle of the
habitable zone. However, the impact of ocean dynamics on the habitable zone's
boundaries (inner edge and outer edge) is still unknown and represents a major
gap in our understanding of this type of planets. Here we use a coupled
atmosphere-ocean global climate model to show that planetary heat transport
from the day to night side is dominated by the ocean at lower stellar fluxes
and by the atmosphere near the inner edge of the habitable zone. This decrease
in oceanic heat transport (OHT) at high stellar fluxes is mainly due to
weakening of surface wind stress and a decrease in surface shortwave energy
deposition. We further show that ocean dynamics have almost no effect on the
observational thermal phase curves of planets near the inner edge of the
habitable zone. For planets in the habitable zone's middle range, ocean
dynamics moves the hottest spot on the surface eastward from the substellar
point. These results suggest that future studies of the inner edge may devote
computational resources to atmosphere-only processes such as clouds and
radiation. For studies of the middle range and outer edge of the habitable
zone, however, fully coupled ocean-atmosphere modeling will be necessary. Note
that due to computational resource limitations, only one rotation period (60
Earth days) has been systematically examined in this study; future work varying
rotation period as well as other parameters such as atmospheric mass and
composition is required.Comment: 34 pages, 13 figures, and 1 tabl
Semileptonic decays of baryons in a relativistic quark model
We calculate semileptonic decays of light and heavy baryons in a
relativistically covariant constituent quark model. The model is based on the
Bethe-Salpeter-equation in instantaneous approximation. It generates
satisfactory mass spectra for mesons and baryons up to the highest observable
energies. Without introducing additional free parameters we compute on this
basis helicity amplitudes of electronic and muonic semileptonic decays of
baryons. We thus obtain form factor ratios and decay rates in good agreement
with experiment.Comment: 8 pages, 10 figures, 2 tables, typos remove
Demarcating circulation regimes of synchronously rotating terrestrial planets within the habitable zone
We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model (CAM). The surface temperature contrast between day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen on gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from day to night side, with both the Rossby deformation radius and the Rhines length exceeding planetary radius, which occurs for planets around stars with effective temperatures of 3300 K to 4500 K (rotation period > 20 days). Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, with the Rossby deformation radius is less than planetary radius, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period < 5 days). In between is the Rhines rotation regime, which retains a thermally-direct circulation from day to night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000 K to 3300 K (rotation period ∼ 5 to 20 days), where the Rhines length is greater than planetary radius but the Rossby deformation radius is less than planetary radius. The dynamical state can be observationally inferred from comparing the morphology of the thermal emission phase curves of synchronously rotating planets
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