Generation of internal gravity waves by penetrative convection

The rich harvest of seismic observations over the past decade provides evidence of angular momentum redistribution in stellar interiors that is not reproduced by current evolution codes. In this context, transport by internal gravity waves can play a role and could explain discrepancies between theory and observations. The efficiency of the transport of angular momentum by waves depends on their driving mechanism. While excitation by turbulence throughout the convective zone has already been investigated, we know that penetrative convection into the stably stratified radiative zone can also generate internal gravity waves. Therefore, we aim at developing a semianalytical model to estimate the generation of IGW by penetrative plumes below an upper convective envelope. We derive the wave amplitude considering the pressure exerted by an ensemble of plumes on the interface between the radiative and convective zones as source term in the equation of momentum. We consider the effect of a thermal transition from a convective gradient to a radiative one on the transmission of the wave into the radiative zone. The plume-induced wave energy flux at the top of the radiative zone is computed for a solar model and is compared to the turbulence-induced one. We show that, for the solar case, penetrative convection generates waves more efficiently than turbulence and that plume-induced waves can modify the internal rotation rate on shorter time scales. We also show that a smooth thermal transition significatively enhances the wave transmission compared to the case of a steep transition. We conclude that driving by penetrative convection must be taken into account as much as turbulence-induced waves for the transport of internal angular momentum.Comment: Accepted for publication in A&A, 21 page

A simple representation of oscillation modes in stars: from mixed modes coupling to glitches

Analytical resonance conditions for oscillation modes in stars are very helpful both to predict and to examine their frequency spectra, as well as to make the link with their internal properties. In this short paper, we introduce a general quantization expression for oscillation modes accounting for the possible existence of a local sharp variation in the equilibrium structure, a so-called glitch. This representation is based on a direct adaptation of the progressive-wave picture of mixed modes proposed by Takata (2016b). In this formulation, a glitch turns out to be characterized by three parameters: its acoustic depth, the phase lags introduced after the wave reflection at the considered point, and a coupling factor. Such an expression has two main advantages. First, it can be easily applicable to a lot of different structural configurations. Second, it does not assume that the glitch is a small perturbation. Actually, we check that the obtained expression tends to the formulations previously derived when the glitch is weak. These research notes represent a preliminary step towards a more generalized description of multi-cavity oscillation modes, that was briefly addressed in the poster presented at the PHOST conference.Comment: Published 11 December 2018, 4 page

A Qualitative Exploration of the Japanese Public\u27s Response to the Fukushima Nuclear Disaster

This narrative content analysis was conducted to gain an understanding of the experiences and perspectives of the Japanese public and explore how individuals have responded to and been impacted by the Fukushima nuclear disaster. After application of selection criteria, content from one alternative media website - Fukushima Diary - became identified as a source of data in this study. In all, 841 single-spaced pages of data analyzed to further understanding of the public\u27s cognitive, affective, and behavioral responses to the health threat posed by the Fukushima nuclear catastrophe resulted in identification of six themes arranged according to two dimensions. The first dimension, when the impossible happens, consists of three themes centered on the public\u27s affective and cognitive responses: (a) a shock to the system, (b) increasing perception of threat, and (c) betrayal and systemic domination. The second dimension, we have to save ourselves, includes three themes highlighting the public\u27s behavioral responses: (a) the mosquito and the dinosaur, (b) two kinds of people, and (c) a butterfly trying to move a mountain. Collectively, these six themes reveal how this disaster has impacted the wellbeing of those living in Japan and illuminate the centrality of culture and communication to the Japanese public\u27s understanding of and response to this nuclear catastrophe. Findings confirm the heuristic value of the EPPM and the five cultural dimensions in Hofstede\u27s framework. As an emergent theory, Iori Mochizuki\u27s self-hypnosis model provided a valuable lens for furthering understanding of how this disaster impacted the Japanese public. As suggested by this research, the Japanese response to the Fukushima nuclear disaster remains highly heterogeneous. While statistics on overall releases of radiation provide an essential objective measure of the severity and potential impact of the disaster, this study illuminates the value of examining detailed narrative accounts when seeking to understand the human toll of this catastrophe

La métallurgie du fer : technique, symbolique et sémantique : symbolique obstétrique et dynamique de la contradiction en Afrique centrale

Les métallurgistes africains accordent une grande importance à ce qui est convenu d'appeler des procédures magiques. La variété des gestes symboliques révélée par notre inventaire bibliographique repose sur une base commune, l'activité sémantique, entendue comme production de sens pour orienter l'action. La métaphore obstétrique, toujours présente, ne doit pas occulter le travail sémantique dont elle est issue. L'efficacité technique apparaît sous-entendue par une dynamique de la contradiction qui rapproche temporairement des éléments définis comme distincts et opposés dans la vie ordinaire. (Résumé d'auteur

Angles-sur-l'Anglin – Le Roc-aux-Sorciers

Identifiant de l'opération archéologique : 204078 Date de l'opération : 2008 (RE) Inventeur(s) : Pinçon Geneviève (MCC) Le gisement magdalénien du Roc-aux-Sorciers à Angles-sur-l'Anglin (Vienne) est célèbre pour son ensemble pariétal sculpté, gravé et peint associé à des vestiges d’occupation . La configuration du site offre deux espaces, correspondants aux aires de fouilles de Suzanne de Saint-Mathurin qui a mis au jour ces œuvres dans les années 1950. Dans la partie amont, la cave Taille..

Norme et individualité au Roc-aux-Sorciers (Vienne, France) : approche des "mains" du registre animalier au travers de la forme

International audienceOccupé à diverses reprises au cours du Magdalénien moyen (18.000-16.000 cal. BP), l'abri du Roc-aux-Sorciers (Vienne, France) doit sa renommée à la richesse de son art pariétal, gravé, peint et sculpté, associant figurations humaines et animales. Au sein du registre sculpté, l'analyse stylistique des représentations animales met en évidence d'une part une forte homogénéité des codes graphiques, d'autre part de discrètes variations formelles affectant certains éléments anatomiques. Deux ensembles sculptés se succédant sur la paroi, une partie de cette variabilité résulterait d'une légère évolution des codes graphiques au cours de l'occupation du site. Cependant, à l'intérieur des deux ensembles sculptés, chaque animal s'individualise par des attributs formels spécifiques (oreilles, naseaux) qui pourraient alors illustrer la créativité de l'auteur. Cette analyse stylistique soulève ainsi la question de la part respective de l'expression individuelle et des normes collective dans l'iconographie de l'art pariétal au Magdalénien moyen. Elle est aussi l'occasion d'aborder le problème de l'identification de « mains » à travers des critères formels

Amplitude of solar gravity modes generated by penetrative plumes

The detection of gravity modes is expected to give us unprecedented insights into the inner dynamics of the Sun. Within this framework, predicting their amplitudes is essential to guide future observational strategies and seismic studies. In this work, we predict the amplitude of low-frequency asymptotic gravity modes generated by penetrative convection at the top of the radiative zone. The result is found to depend critically on the time evolution of the plumes inside the generation region. Using a solar model, we compute the GOLF apparent surface radial velocity of low-degree gravity modes in the frequency range $10~\mu H_z\le \nu \le 100~\mu H_z$. In case of a Gaussian plume time evolution, gravity modes turn out to be undetectable because of too small surface amplitudes. This holds true despite a wide range of values considered for the parameters of the model. In the other limiting case of an exponential time evolution, plumes are expected to drive gravity modes in a much more efficient way because of a much higher temporal coupling between the plumes and the modes than in the Gaussian case. Using reasonable values for the plume parameters based on semi-analytical models, the apparent surface velocities in this case turn out to be one order of magnitude smaller than the 22-years GOLF detection threshold and than the previous estimates considering turbulent pressure as the driving mechanism, with a maximum value of $0.05$ cm s${}^{-1}$ for $\ell =1$ and $\nu\approx 100~\mu H_z$. When accounting for uncertainties on the plume parameters, the apparent surface velocities in the most favorable plausible case become comparable to those predicted with turbulent pressure, and the GOLF observation time required for a detection at $\nu \approx100~\mu H_z$ and $\ell=1$ is reduced to about 50 yrs.Comment: 18 pages, Accepted for publication in A&