scholarly journals Baroclinic generation of potential vorticity in an embedded planet-disk system

2007 ◽  
Vol 3 (S249) ◽  
pp. 407-412
Author(s):  
Jianghui JI ◽  
Shangli OU ◽  
Lin LIU
Keyword(s):  
Potential Vorticity ◽  
Gravitational Interaction ◽  
Baroclinic Instability ◽  
Giant Planet ◽  
Time Behavior ◽  
Habitable Zone ◽  
Local Minima ◽  
Disk System ◽  
Earth Like Planets ◽  
Orbital Migration

AbstractWe use a multi-dimensional hydrodynamics code to study the gravitational interaction between an embedded planet and a protoplanetary disk with emphasis on the generation of vortensity (Potential Vorticity or PV) through a Baroclinic Instability. We show that the generation of PV is very common and effective in non-barotropic disks through the Baroclinic Instability, especially within the coorbital region. Our results also complement previous work that non-axisymmetric Rossby-Wave Instabilities (RWIs) are likely to develop at local minima of PV distribution that are generated by the interaction between a planet and an inviscid barotropic disk. The development of RWIs results in non-axisymmetric density blobs, which exert stronger torques onto the planet when they move to the vicinity of the planet. Hence, large amplitude oscillations are introduced to the time behavior of the total torque acted on the planet by the disk. In current simulations, RWIs do not change the overall picture of inward orbital migration but cause a non-monotonic behavior to the migration speed. As a side effect, RWIs also introduce interesting structures into the disk. These structures may help the formation of Earth-like planets in the Habitable Zone or Hot Earths interior to a close-in giant planet.

scholarly journals Resilient habitability of nearby exoplanet systems

2019 ◽  
Vol 492 (1) ◽  
pp. 352-368 ◽  
Author(s):  
Giorgi Kokaia ◽  
Melvyn B Davies ◽  
Alexander J Mustill
Keyword(s):  
Giant Planet ◽  
Planetary Systems ◽  
Observational Constraints ◽  
Habitable Zone ◽  
Habitable Zones ◽  
Test Particles ◽  
Planetary Orbits ◽  
Two Systems ◽  
Earth Like Planets ◽  
Exoplanet Systems

ABSTRACT We investigate the possibility of finding Earth-like planets in the habitable zone of 34 nearby FGK-dwarfs, each known to host one giant planet exterior to their habitable zone detected by RV. First we simulate the dynamics of the planetary systems in their present day configurations and determine the fraction of stable planetary orbits within their habitable zones. Then, we postulate that the eccentricity of the giant planet is a result of an instability in their past during which one or more other planets were ejected from the system. We simulate these scenarios and investigate whether planets orbiting in the habitable zone survive the instability. Explicitly we determine the fraction of test particles, originally found in the habitable zone, which remain in the habitable zone today. We label this fraction the resilient habitability of a system. We find that for most systems the probability of planets existing [or surviving] on stable orbits in the habitable zone becomes significantly smaller when we include a phase of instability in their history. We present a list of candidate systems with high resilient habitability for future observations. These are: HD 95872, HD 154345, HD 102843, HD 25015, GJ 328, HD 6718, and HD 150706. The known planets in the last two systems have large observational uncertainties on their eccentricities, which propagate into large uncertainties on their resilient habitability. Further observational constraints of these two eccentricities will allow us to better constrain the survivability of Earth-like planets in these systems.

scholarly journals Late Time Attractors of Some Varying Chaplygin Gas Cosmological Models

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 769
Author(s):  
Martiros Khurshudyan ◽  
Ratbay Myrzakulov
Keyword(s):  
Dark Energy ◽  
Gravitational Interaction ◽  
Chaplygin Gas ◽  
Cosmological Models ◽  
Late Time ◽  
Time Behavior ◽  
Coincidence Problem ◽  
Energy Models ◽  
Non Linear ◽  
Bayesian Machine Learning

The goal of this paper is to study new cosmological models where the dark energy is a varying Chaplygin gas. This specific dark energy model with non-linear EoS had been often discussed in modern cosmology. Contrary to previous studies, we consider new forms of non-linear non-gravitational interaction between dark matter and assumed dark energy models. We applied the phase space analysis allowing understanding the late time behavior of the models. It allows demonstrating that considered non-gravitational interactions can solve the cosmological coincidence problem. On the other hand, we applied Bayesian Machine Learning technique to learn the constraints on the free parameters. In this way, we gained a better understanding of the models providing a hint which of them can be ruled out. Moreover, the learning based on the simulated expansion rate data shows that the models cannot solve the H0 tension problem.

scholarly journals Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

The habitable zone of Earth-mass planets around 47 UMa: results for land and water worlds

2003 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
S. Franck ◽  
M. Cuntz ◽  
W. von Bloh ◽  
C. Bounama
Keyword(s):  
Surface Water ◽  
System Approach ◽  
Distinct Type ◽  
Integrated System ◽  
Habitable Zone ◽  
Stable Orbit ◽  
The Earth ◽  
Earth Like Planets ◽  
Very High

In a previous paper, we showed that Earth-type habitable planets around 47 UMa are in principle possible if a distinct set of conditions is warranted. These conditions include that the Earth-type planets have successfully formed and are orbitally stable and, in addition, that the 47 UMa star–planet system is relatively young ([lsim ]6 Gyr). We now extend this study by considering Earth-like planets with different land/ocean coverages. This study is again based on the so-called integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical and geodynamical processes. This approach implies a special characterization of the habitable zone defined for a distinct type of planet. We show that the likelihood of finding a habitable Earth-like planet on a stable orbit around 47 UMa critically depends on the percentage of the planetary land/ocean coverage. The likelihood is significantly increased for planets with a very high percentage of ocean surface (‘water worlds’).

scholarly journals Jet Formation and Evolution in Baroclinic Turbulence with Simple Topography

2010 ◽  
Vol 40 (2) ◽  
pp. 257-278 ◽  
Author(s):  
Andrew F. Thompson
Keyword(s):  
Southern Ocean ◽  
Potential Vorticity ◽  
Baroclinic Instability ◽  
Length Scale ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Jet Formation ◽  
Meridional Transport ◽  
Jet Behavior ◽  
Jet Variability

Abstract Satellite altimetry and high-resolution ocean models indicate that the Southern Ocean comprises an intricate web of narrow, meandering jets that undergo spontaneous formation, merger, and splitting events, as well as rapid latitude shifts over periods of weeks to months. The role of topography in controlling jet variability is explored using over 100 simulations from a doubly periodic, forced-dissipative, two-layer quasigeostrophic model. The system is forced by a baroclinically unstable, vertically sheared mean flow in a domain that is large enough to accommodate multiple jets. The dependence of (i) meridional jet spacing, (ii) jet variability, and (iii) domain-averaged meridional transport on changes in the length scale and steepness of simple sinusoidal topographical features is analyzed. The Rhines scale, ℓβ = 2πVe/β, where Ve is an eddy velocity scale and β is the barotropic potential vorticity gradient, measures the meridional extent of eddy mixing by a single jet. The ratio ℓβ /ℓT, where ℓT is the topographic length scale, governs jet behavior. Multiple, steady jets with fixed meridional spacing are observed when ℓβ ≫ ℓT or when ℓβ ≈ ℓT. When ℓβ < ℓT, a pattern of perpetual jet formation and jet merger dominates the time evolution of the system. Zonal ridges systematically reduce the domain-averaged meridional transport, while two-dimensional, sinusoidal bumps can increase transport by an order of magnitude or more. For certain parameters, bumpy topography gives rise to periodic oscillations in the jet structure between purely zonal and topographically steered states. In these cases, transport is dominated by bursts of mixing associated with the transition between the two regimes. Topography modifies local potential vorticity (PV) gradients and mean flows; this can generate asymmetric Reynolds stresses about the jet core and can feed back on the conversion of potential energy to kinetic energy through baroclinic instability. Both processes contribute to unsteady jet behavior. It is likely that these processes play a role in the dynamic nature of Southern Ocean jets.

scholarly journals Potential Vorticity Diagnostics to Quantify Effects of Latent Heating in Extratropical Cyclones. Part I: Methodology

2017 ◽  
Vol 74 (11) ◽  
pp. 3567-3590 ◽  
Author(s):  
Dominik Büeler ◽  
Stephan Pfahl
Keyword(s):  
Potential Vorticity ◽  
Weather Prediction ◽  
Baroclinic Instability ◽  
Numerical Weather Prediction Model ◽  
Cloud Formation ◽  
Extratropical Cyclones ◽  
Latent Heating ◽  
Strongly Coupled ◽  
Cyclone Intensity ◽  
Diabatic Processes

Abstract Extratropical cyclones develop because of baroclinic instability, but their intensification is often substantially amplified by diabatic processes, most importantly, latent heating (LH) through cloud formation. Although this amplification is well understood for individual cyclones, there is still need for a systematic and quantitative investigation of how LH affects cyclone intensification in different, particularly warmer and moister, climates. For this purpose, the authors introduce a simple diagnostic to quantify the contribution of LH to cyclone intensification within the potential vorticity (PV) framework. The two leading terms in the PV tendency equation, diabatic PV modification and vertical advection, are used to derive a diagnostic equation to explicitly calculate the fraction of a cyclone’s positive lower-tropospheric PV anomaly caused by LH. The strength of this anomaly is strongly coupled to cyclone intensity and the associated impacts in terms of surface weather. To evaluate the performance of the diagnostic, sensitivity simulations of 12 Northern Hemisphere cyclones with artificially modified LH are carried out with a numerical weather prediction model. Based on these simulations, it is demonstrated that the PV diagnostic captures the mean sensitivity of the cyclones’ PV structure to LH as well as parts of the strong case-to-case variability. The simple and versatile PV diagnostic will be the basis for future climatological studies of LH effects on cyclone intensification.

scholarly journals Marginal Sea Overflows and the Upper Ocean Interaction

2009 ◽  
Vol 39 (2) ◽  
pp. 387-403 ◽  
Author(s):  
Shinichiro Kida ◽  
Jiayan Yang ◽  
James F. Price
Keyword(s):  
Ocean Circulation ◽  
Potential Vorticity ◽  
Baroclinic Instability ◽  
Upper Ocean ◽  
Marginal Sea ◽  
The Mediterranean ◽  
The Difference ◽  
Set Up ◽  
Numerical Model Experiments ◽  
Gyre Circulation

Abstract Marginal sea overflows and the overlying upper ocean are coupled in the vertical by two distinct mechanisms—by an interfacial mass flux from the upper ocean to the overflow layer that accompanies entrainment and by a divergent eddy flux associated with baroclinic instability. Because both mechanisms tend to be localized in space, the resulting upper ocean circulation can be characterized as a β plume for which the relevant background potential vorticity is set by the slope of the topography, that is, a topographic β plume. The entrainment-driven topographic β plume consists of a single gyre that is aligned along isobaths. The circulation is cyclonic within the upper ocean (water columns are stretched). The transport within one branch of the topographic β plume may exceed the entrainment flux by a factor of 2 or more. Overflows are likely to be baroclinically unstable, especially near the strait. This creates eddy variability in both the upper ocean and overflow layers and a flux of momentum and energy in the vertical. In the time mean, the eddies accompanying baroclinic instability set up a double-gyre circulation in the upper ocean, an eddy-driven topographic β plume. In regions where baroclinic instability is growing, the momentum flux from the overflow into the upper ocean acts as a drag on the overflow and causes the overflow to descend the slope at a steeper angle than what would arise from bottom friction alone. Numerical model experiments suggest that the Faroe Bank Channel overflow should be the most prominent example of an eddy-driven topographic β plume and that the resulting upper-layer transport should be comparable to that of the overflow. The overflow-layer eddies that accompany baroclinic instability are analogous to those observed in moored array data. In contrast, the upper layer of the Mediterranean overflow is likely to be dominated more by an entrainment-driven topographic β plume. The difference arises because entrainment occurs at a much shallower location for the Mediterranean case and the background potential vorticity gradient of the upper ocean is much larger.

scholarly journals Formation of single-moon systems around gas giants

2020 ◽  
Vol 635 ◽  
pp. L4 ◽  
Author(s):  
Yuri I. Fujii ◽  
Masahiro Ogihara
Keyword(s):  
Giant Planet ◽  
Orbital Evolution ◽  
Effect Of Temperature ◽  
Temperature Structure ◽  
Satellite Formation ◽  
Satellite Systems ◽  
Evolution Stage ◽  
First Time ◽  
Final Evolution ◽  
Orbital Migration

Context. Several mechanisms have been proposed to explain the formation process of satellite systems, and relatively large moons are thought to be born in circumplanetary disks. Making a single-moon system is known to be more difficult than multiple-moon or moonless systems. Aims. We aim to find a way to form a system with a single large moon, such as Titan around Saturn. We examine the orbital migration of moons, which change their direction and speed depending on the properties of circumplanetary disks. Methods. We modeled dissipating circumplanetary disks with taking the effect of temperature structures into account and calculated the orbital evolution of Titan-mass satellites in the final evolution stage of various circumplanetary disks. We also performed N-body simulations of systems that initially had multiple satellites to see whether single-moon systems remained at the end. Results. The radial slope of the disk-temperature structure characterized by the dust opacity produces a patch of orbits in which the Titan-mass moons cease inward migration and even migrate outward in a certain range of the disk viscosity. The patch assists moons initially located in the outer orbits to remain in the disk, while those in the inner orbits fall onto the planet. Conclusions. We demonstrate for the first time that systems can form that have only one large moon around giant planet. Our N-body simulations suggest satellite formation was not efficient in the outer radii of circumplanetary disks.

Interactions between Water Vapor and Potential Vorticity in Synoptic-Scale Monsoonal Disturbances: Moisture Vortex Instability

2018 ◽  
Vol 75 (6) ◽  
pp. 2083-2106 ◽  
Author(s):  
Ángel F. Adames ◽  
Yi Ming
Keyword(s):  
Potential Vorticity ◽  
Baroclinic Instability ◽  
Relative Role ◽  
Synoptic Scale ◽  
Vortex Instability ◽  
Tropical Variability ◽  
Moisture Advection ◽  
Energy Gradient ◽  
Gross Moist Stability ◽  
Static Energy

AbstractSouth Asian monsoon low pressure systems, referred to as synoptic-scale monsoonal disturbances (SMDs), are convectively coupled cyclonic disturbances that are responsible for up to half of the total monsoon rainfall. In spite of their importance, the mechanisms that lead to the growth of these systems have remained elusive. It has long been thought that SMDs grow because of a variant of baroclinic instability that includes the effects of convection. Recent work, however, has shown that this framework is inconsistent with the observed structure and dynamics of SMDs. Here, we present an alternative framework that may explain the growth of SMDs and may also be applicable to other modes of tropical variability. Moisture is prognostic and is coupled to precipitation through a simplified Betts–Miller scheme. Interactions between moisture and potential vorticity (PV) in the presence of a moist static energy gradient can be understood in terms of a “gross” PV (qG) equation. The qG summarizes the dynamics of SMDs and reveals the relative role that moist and dry dynamics play in these disturbances, which is largely determined by the gross moist stability. Linear solutions to the coupled PV and moisture equations reveal Rossby-like modes that grow because of a moisture vortex instability. Meridional temperature and moisture advection to the west of the PV maximum moisten and destabilize the column, which results in enhanced convection and SMD intensification through vortex stretching. This instability occurs only if the moistening is in the direction of propagation of the SMD and is strongest at the synoptic scale.

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