941 research outputs found
Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences. II. Comparison with Observations
The full-phase infrared light curves of low-eccentricity hot Jupiters show a
trend of increasing fractional dayside-nightside brightness temperature
difference with increasing incident stellar flux, both averaged across the
infrared and in each individual wavelength band. The analytic theory of Komacek
& Showman (2016) shows that this trend is due to the decreasing ability with
increasing incident stellar flux of waves to propagate from day to night and
erase temperature differences. Here, we compare the predictions of this theory
to observations, showing that it explains well the shape of the trend of
increasing dayside-nightside temperature difference with increasing equilibrium
temperature. Applied to individual planets, the theory matches well with
observations at high equilibrium temperatures but, for a fixed photosphere
pressure of , systematically under-predicts the
dayside-nightside brightness temperature differences at equilibrium
temperatures less than . We interpret this as due to as the
effects of a process that moves the infrared photospheres of these cooler hot
Jupiters to lower pressures. We also utilize general circulation modeling with
double-grey radiative transfer to explore how the circulation changes with
equilibrium temperature and drag strengths. As expected from our theory, the
dayside-nightside temperature differences from our numerical simulations
increase with increasing incident stellar flux and drag strengths. We calculate
model phase curves using our general circulation models, from which we compare
the broadband infrared offset from the substellar point and dayside-nightside
brightness temperature differences against observations, finding that strong
drag or additional effects (e.g. clouds and/or supersolar metallicities) are
necessary to explain many observed phase curves.Comment: Accepted at ApJ, 16 pages, 11 figure
Vertical Tracer Mixing in Hot Jupiter Atmospheres
Aerosols appear to be ubiquitous in close-in gas giant atmospheres, and
disequilibrium chemistry likely impacts the emergent spectra of these planets.
Lofted aerosols and disequilibrium chemistry are caused by vigorous vertical
transport in these heavily irradiated atmospheres. Here we numerically and
analytically investigate how vertical transport should change over the
parameter space of spin-synchronized gas giants. In order to understand how
tracer transport depends on planetary parameters, we develop an analytic theory
to predict vertical velocities and mixing rates () and compare
the results to our numerical experiments. We find that both our theory and
numerical simulations predict that, if the vertical mixing rate is described by
an eddy diffusivity, then this eddy diffusivity should increase
with increasing equilibrium temperature, decreasing frictional drag strength,
and increasing chemical loss timescales. We find that the transition in our
numerical simulations between circulation dominated by a superrotating jet and
that with solely day-to-night flow causes a marked change in the vertical
velocity structure and tracer distribution. The mixing ratio of passive tracers
is greatest for intermediate drag strengths that corresponds to this transition
between a superrotating jet with columnar vertical velocity structure and
day-to-night flow with upwelling on the dayside and downwelling on the
nightside. Lastly, we present analytic solutions for as a
function of planetary effective temperature, chemical loss timescales, and
other parameters, for use as input to one-dimensional chemistry models of
spin-synchronized gas giant atmospheres.Comment: 25 pages, 12 figures, Accepted at Ap
Microwave observations of sea state from aircraft
Airborne microwave radiometer measurements of thermal radiances over sea surface
Attention Deficit Hyperactivity Disorder (ADHD) and Other Neurocognitive Factors Contributing to Road Traffic Accidents (RTA)
Road traffic accidents (RTAs) are among the leading causes of mortality worldwide. RTAs are multifactorial in origin, but neurocognitive function of drivers contributes about 25% of the variance of most accidents. This chapter reviews the commonest disorders that contribute to RTA. They are attention deficit hyperactivity disorder (ADHD), specific learning disabilities (e.g., dyslexia), autism spectrum disorder (ASD) in adolescents and young adult drivers, and mild cognitive impairment (MCI) and dementia in older drivers. The features of these disorders and how they impair driving along with evidence-based treatments and interventions are discussed. Increasing awareness of these disorders, screening for them, and offering treatment when appropriate can contribute to reducing the disease burden related to RTA, which is currently the eighth leading cause of death across all ages globally. The lack of attention to these disorders within the road safety disciplines constitutes a significant public health problem which requires attention
Star formation in Carina OB1: Observations of a giant molecular cloud associated with the eta Carinae Nebula
A giant molecular cloud associated with the eta Carinae nebula was fully mapped in CO with the Columbia Millimeter-Wave Telescope at Cerro Tololo. The cloud comples has a mass of roughly 700,000 solar mass and extends about 140 pc along the Galactic plane, with the giant Carina HII region situated at one end of the complex. Clear evidence of interaction between the HII region and the molecular cloud is found in the relative motions of the ionized gas, the molecular gas, and the dust; simple energy and momentum considerations suggest that the HII region is responsible for the observed motion of a cloud fragment. The molecular cloud complex appears to be the parent material of the entire Car OB1 Association which, in addition to the young clusters in the Carine nebula, includes the generally older cluster NGC 3325, NGC 3293, and IC 2581. The overall star formation efficiency in the cloud complex is estimated to be approximately 0.02
Rotational Spectroscopy of PAHs: Acenaphthene, Acenaphthylene and Fluorene
Pure rotational spectra of three polycyclic aromatic hydrocarbons -
acenaphthene, acenaphthylene and fluorene - have been obtained by Fourier
transform microwave spectroscopy of a molecular beam and subsequently by
millimeter wave absorption spectroscopy for acenaphthene and fluorene. The data
presented here will be useful for deep radio astronomical searches for PAHs
employing large radio telecopes.Comment: 2 pages, 1 figure (uses iaus.sty), to appear in IAU Symposium No.
231, Astrochemistry - Recent Successes and Current Challenges, eds. D. C.
Lis, G. A. Blake & E. Herbst (Cambridge Univ. Press
Indirect observation of unobservable interstellar molecules
It is suggested that the abundances of neutral non-polar interstellar molecules unobservable by radio astronomy can be systematically determined by radio observation of the protonated ions. As an example, observed N2H(+) column densities are analyzed to infer molecular nitrogen abundances in dense interstellar clouds. The chemistries and expected densities of the protonated ions of O2, C2, CO2, C2H2 and CH4 are then discussed. Microwave transition frequencies fo HCO2(+) and C2H3(+) are estimated, and a preliminary astronomical search for HCO2(+) is described
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