Understanding tidal dissipation in gaseous giant planets from their core to their surface

Tidal dissipation in planetary interiors is one of the key physical mechanisms that drive the evolution of star-planet and planet-moon systems. Tidal dissipation in planets is intrinsically related to their internal structure. In particular, fluid and solid layers behave differently under tidal forcing. Therefore, their respective dissipation reservoirs have to be compared. In this work, we compute separately the contributions of the potential dense rocky/icy core and of the convective fluid envelope of gaseous giant planets, as a function of core size and mass. We demonstrate that in general both mechanisms must be taken into account.Comment: 2 pages, 2 figures, CoRoT Symposium 3 / Kepler KASC-7 joint meeting, Toulouse, July 2014; To be published by EPJ Web of Conference

The 2D dynamics of radiative zones of low-mass stars

In the context of secular evolution, we describe the dynamics of the radiative core of low-mass stars to understand the internal transport of angular momentum in such stars which results in a solid rotation in the Sun from 0.7R_sun to 0.2R_sun and a weak radial core-envelope differential rotation in solar-type stars. This study requires at least a 2D description to capture the latitudinal variations of the differential rotation. We build 2D numerical models of a radiative core on the top of which we impose a latitudinal shear so as to reproduce a cylindrical differential rotation in a convective envelope. We perform a systematic study over the Rossby number measuring the latitudinal differential rotation at the radiative-convective interface. The imposed shear generates a geostrophic flow implying a cylindrical differential rotation. When compared to the baroclinic flow that arises from the stable stratification, we find that the geostrophic flow is dominant when the Rossby number is high enough with a cylindrical rotation profile. For low Rossby numbers, the baroclinic solution dominates with a quasi-shellular rotation profile. Using scaling laws from 3D simulations, we show that slow rotators are expected to have a cylindrical rotation profile. Fast rotators may have a shellular profile at the beginning of the main-sequence in stellar radiative zones. This study enables us to predict different types of differential rotation and emphasizes the need of a new generation of 2D rotating stellar models developed in synergy with 3D numerical simulations. The shear induced by a surface convective zone has a strong impact on the dynamics of the underlying radiative zone in low-mass stars. But, it cannot produce a flat internal rotation profile in a solar configuration calling for additional processes for the transport of angular momentum in both radial and latitudinal directions.Comment: 12 pages, 7 figures, accepted for publication in A&

Tidal inertial waves in the differentially rotating convective envelopes of low-mass stars - I. Free oscillation modes

Star-planet tidal interactions may result in the excitation of inertial waves in the convective region of stars. In low-mass stars, their dissipation plays a prominent role in the long-term orbital evolution of short-period planets. Turbulent convection can sustain differential rotation in their envelope, with an equatorial acceleration (as in the Sun) or deceleration, which can modify the waves' propagation properties. We explore in this first paper the general propagation properties of free linear inertial waves in a differentially rotating homogeneous fluid inside a spherical shell. We assume that the angular velocity background flow depends on the latitudinal coordinate only, close to what is expected in the external convective envelope of low-mass stars. We use i) an analytical approach in the inviscid case to get the dispersion relation, from which we compute the characteristic trajectories along which energy propagates. This allows us to study the existence of attractor cycles and infer the different families of inertial modes; ii) high-resolution numerical calculations based on a spectral method for the viscous problem. We find that modes that propagate in the whole shell (D modes) behave the same way as with solid-body rotation. However, another family of inertial modes exists (DT modes), which can propagate only in a restricted part of the convective zone. Our study shows that they are less common than D modes and that the characteristic rays and shear layers often focus towards a wedge - or point-like attractor. More importantly, we find that for non-axisymmetric oscillation modes, shear layers may cross a corotation resonance with a local accumulation of kinetic energy. Their damping rate scales very differently from what we obtain for standard D modes and we show an example where it is independent of viscosity (Ekman number) in the astrophysical regime in which it is small.Comment: 17 pages, 15 figures, accepted for publication in A&

Prescription Drug Abuse and Provider-Patient Communication: A Qualitative Analysis of the Perspectives of Prescribers and Patients

Prescription drug abuse is a public health problem of epidemic proportions in the United States. Provider-patient communication underpins many initiatives aimed at preventing and reducing the public health burden of prescription drug abuse. The characteristics of and factors contributing to this interpersonal process, however, have not been fully explored. The purpose of this research was to examine: 1) the overall problem of prescription drug abuse and provider-patient communication about prescription drug abuse from the patient perspective; and 2) provider-patient communication about prescription drug abuse from the prescriber perspective. In 2014-2015, semi-structured interviews were conducted with 20 patients from primary care and addiction medicine and 10 prescribers from multiple health professions and medical fields in Central and South Central Appalachia. The interviews were audio-recorded and transcribed verbatim. Thematic analysis, facilitated by qualitative data analysis software, was used to generate themes. Patients perceived prescription drug abuse as a problem, both in terms of its prevalence and contribution to negative consequences. Patients connected abuse to accessibility, identifying routes of access, routine practices, and rationales involved in the acquisition and distribution of prescription drugs for abuse. With regard to provider-patient communication, patients reported different levels of engagement in prescription drug abuse-related communication with healthcare providers—active, passive, and no/limited. Prescribers likewise reported different patterns of prescription drug abuse-related communication with patients—informative, counteractive, and supportive. Collectively, patients and prescribers described a range of factors—personal and environmental—that positively and negatively influence provider-patient communication and, by association, prescriber delivery and patient receipt of healthcare related to prescription drug abuse. When comparing the perspectives of patients and prescribers, multiple similarities in their prescription drug abuse-related communication perceptions and behaviors were identified. The findings of this research have implications for: 1) clinical practice to mitigate prescription drug abuse and improve patient prescription drug abuse-related communication behaviors; 2) patient- and prescriber-targeted interventions to improve provider-patient communication about prescription drug abuse; and 3) future research to continue to advance understanding of provider-patient communication about prescription drug abuse