Solar wind turbulent spectrum at plasma kinetic scales

The description of the turbulent spectrum of magnetic fluctuations in the solar wind in the kinetic range of scales is not yet completely established. Here, we perform a statistical study of 100 spectra measured by the STAFF instrument on the Cluster mission, which allows to resolve turbulent fluctuations from ion scales down to a fraction of electron scales, i.e. from $\sim 10^2$ km to $\sim 300$ m. We show that for $k_{\perp}\rho_e \in[0.03,3]$ (that corresponds approximately to the frequency in the spacecraft frame $f\in [3,300]$ Hz), all the observed spectra can be described by a general law $E(k_\perp)\propto k_\perp^{-8/3}\exp{(-k_\perp \rho_e)}$, where $k_{\perp}$ is the wave-vector component normal to the background magnetic field and $\rho_e$ the electron Larmor radius. This exponential tail found in the solar wind seems compatible with the Landau damping of magnetic fluctuations onto electrons.Comment: published in APJ, 15 of November 2012 (with reduced "Discussion" section

Spectra and anisotropy of magnetic fluctuations in the Earth's magnetosheath: Cluster observations

We investigate the spectral shape, the anisotropy of the wave vector distributions and the anisotropy of the amplitudes of the magnetic fluctuations in the Earth's magnetosheath within a broad range of frequencies. We present the first observations of a Kolmogorov-like inertial range of Alfvenic fluctuations in the magnetosheath flanks, below fci. In the vicinity of fci, a spectral break is observed, like in solar wind turbulence. Above the break, the energy of compressive and Alfvenic fluctuations generally follow a power law with a spectral index between -3 and -2. Concerning the anisotropy of the wave vector distribution, we observe a change in its nature in the vicinity of ion characteristic scales: if at MHD scales there is no evidence for a dominance of a slab (k||>kperp) or 2D (kperp>k||) turbulence, above the spectral break, (f>fci, kc/wpi>1) the 2D turbulence dominates. This 2D turbulence is observed in six selected one-hour intervals among which the average proton beta varies from 0.8 to 9. It is observed for both the transverse and compressive magnetic fluctuations, independently on the presence of linearly unstable modes at low frequencies or Alfven vortices at the spectral break. We then analyse the anisotropy of the magnetic fluctuations in a time dependent reference frame based on the field B and the flow velocity V directions. Within the range of the 2D turbulence, at scales [1,30]kc/wpi, and for any beta we find that the magnetic fluctuations at a given frequency in the plane perpendicular to B have more energy along the BxV direction. This non-gyrotropy of the fluctuations is consistent with gyrotropic fluctuations at a given wave vector, with kperp>k||, which suffer a different Doppler shift along and perpendicular to V in the plane perpendicular to B.Comment: accepted for publication in Annales Geophysicae (ANGEO) at 29/09/200

Territorialisation sanitaire et décentralisation : état des lieux et enjeux à partir du cas français

Ces dernières décennies, les transformations des systèmes de santé dans le monde se traduisent par des processus de territorialisation, sous-tendus par trois tendances principales : la régulation financière, le développement des partenariats et le transfert des compétences. Dans ce papier, nous resituons tout d’abord le processus de territorialisation dans le cadre plus général des questions de décentralisation, de gouvernance et de gouvernement. En se focalisant sur le cas français, nous analysons ensuite l’articulation entre la décentralisation dite fonctionnelle en santé et les processus plus généraux de décentralisation des institutions. Pour conclure, nous questionnons les enjeux opérationnels et organisationnels qui en découlent.In this paper, we focus on the common trends of transformations of health care systems in the world. Based on the identification of three logics that root these evolutions (financial regulation, development of cooperation and skill/power transfers), we define territorialization as a process. It refers to projects of planning for which actors implement strategies to produce controlled and bounded spaces. In this process, scales, distances enacted through instruments are involved for putting public policy into practice and space. These actions give rise to different forms of territorialization in which different modes of governance, government and uses are embedded. In a second part, we focus on the case of France and the ways instruments have been used to develop public policies. We insist on the disconnections between the political and administrative decentralization with the evolution of the health sector. The general trend of decentralization of French administration during the eighties is characterized by a greater proximity of public decision with citizen, which involves more action for local authorities. A structured vision of decentralization appears only at the beginning of 2010s based on potential differentiation of standard on the territory and the possibility for regions to provide guidance to others local authorities. During these periods, health sector remains on the sidelines of the legislative evolution. Although regional level was defined as the structuring level of organization for health care in the hospital law of 1991, regionalization of public health policy really operated in 2009 with the Patients, Health and Territories Law (HPST) creating regional health agencies. These ones, with the legal personality are a type of functional decentralization, which are submitted to state monitoring. Concentrating the decision-making power at the regional level and breaking down barriers between sectoral policies, this law simplified local organization of health sector governance. It is operated in a regional health plan which relies on contractual partnerships with a lot of actors including local authorities which became a major actor to decline the plan at the local level. In a third part, we discuss the stakes, options and problems that actors have to face in the current stage of decentralization. Combined with deconcentration of others services, overlapping, cross-financing occurred and involved lower clarity of administrative organization. Two major stakes are identified. Firstly, the capabilities for actors to form a wide coalition sharing objectives and keeping up with changes in stakeholder’s dynamics, like political changeovers and budget cuts. Secondly, a better coordination of actors, in order to create favorable conditions for cooperation and complementarities

Whistler mode waves and the electron heat flux in the solar wind: Cluster observations

The nature of the magnetic field fluctuations in the solar wind between the ion and electron scales is still under debate. Using the Cluster/STAFF instrument, we make a survey of the power spectral density and of the polarization of these fluctuations at frequencies $f\in[1,400]$ Hz, during five years (2001-2005), when Cluster was in the free solar wind. In $\sim 10\%$ of the selected data, we observe narrow-band, right-handed, circularly polarized fluctuations, with wave vectors quasi-parallel to the mean magnetic field, superimposed on the spectrum of the permanent background turbulence. We interpret these coherent fluctuations as whistler mode waves. The life time of these waves varies between a few seconds and several hours. Here we present, for the first time, an analysis of long-lived whistler waves, i.e. lasting more than five minutes. We find several necessary (but not sufficient) conditions for the observation of whistler waves, mainly a low level of the background turbulence, a slow wind, a relatively large electron heat flux and a low electron collision frequency. When the electron parallel beta factor $\beta_{e\parallel}$ is larger than 3, the whistler waves are seen along the heat flux threshold of the whistler heat flux instability. The presence of such whistler waves confirms that the whistler heat flux instability contributes to the regulation of the solar wind heat flux, at least for $\beta_{e\parallel} \ge$ 3, in the slow wind, at 1 AU.Comment: The Astrophysical Journal, 2014, in pres

Rock fall photogrammetric monitoring in the active crater of Piton de la Fournaise volcano, la Reunion Island

International audienceThe collapse of the active crater at Piton de la Fournaise volcano, La Reunion Island, 5th April 2007, offers a rare opportunity to observe frequent rock fall and granular landslides, and test new monitoring techniques. Events concern volumes ranging from single blocks to more massive cliff collapse. The purpose of the presentation is two fold: first, we present a comparison between a Digital Terrain Model (DTM) obtained prior to crater collapse and a DTM extracted from aerial photographs shot in October 2010 (before the eruptive crisis of November 2009 and January 2010). This provides an assessment of morphological changes at the scale of the crater. The second purpose is to describe slope instabilities on the south-western flank of the crater observed since October 2009. These ground-based observations were obtained from a pair of photogrammetric stations deployed along the northern and eastern edges of the crater. These works were conducted within UNDERVOLC project. With this monitoring system we mapped zones affected by rockfalls (departure and accumulation areas) and propose a first estimate of volumes of lava produced by the eruption affecting the inside of the crater since January 2

Les déserts médicaux en Ile-de-France

Mangeney Catherine. Les déserts médicaux en Ile-de-France. In: Villes en parallèle. Documents, n°6,2018. Financiarisation de la ville et liberté du politique. Séminaire Analyse et Politique de la Ville - année 2018-2019. pp. 27-29

Enjeux et défis des zonages prescriptifs de l'action publique, l'exemple des zonages déficitaires en medecins généralistes en France

In France, as in other countries in the world, the difficulties of spatial accessibility to healthcare supply has been a central issue and a priority for public health policies for two decades. Since 2005, French legislation has provided that, in each region, areas considered to be in deficit in terms of medical provision must be identified. Doctors who practice or who come to settle there can benefit from a certain number of public aids, the objective being to promote a better geographical distribution of healthcare supply. Faced with the limited effectiveness of this public policy, the measures implemented are regularly called into question, as is the methodology for delimiting "doctor zoning". This thesis is devoted to questioning this zoning methodology. A preliminary socio-historical detour retracing the process of genesis of this instrument of public action allows us to understand that current physician zoning, in its purely incentive form, is a compromise tool shaped in part by pragmatic issues of which it cannot be disregard. I then demonstrate why, as an instrument of a public policy of positive discrimination, the issues of equity and social and/or spatial justice are essential to the instrument and I explain how current zoning methods are largely conditioned by a presupposition, more fantasized than proven, of a link between territories with difficulties in spatial accessibility to general practitioners and socially disadvantaged territories. So much so that current zoning methods are based on social criteria as much as on the measurement of levels of spatial accessibility to care, which distorts the very function of this zoning, which we no longer know if it targets areas in difficulty of access to care or if it only targets areas in social difficulty. In this thesis, I reintegrate the social dimension of needs into the measurement of levels of spatial accessibility to general practitioners in order to identify, based on the Ile-de-France case, the territories where populations have the most potential difficulties with spatial accessibility et general practitioners taking into account their social characteristics. I explain the underlying choices of the measurement method. Proceeding by scenarios, I show that in Île-de-France, the reality represented differs very significantly according to the parameters integrated into the measurement model, thus underlining the importance of "repoliticizing" the measurement (even before the selection stage) since the norms produced by the underlying choices draw implicitly (while they should translate explicitly) a specific vision of where we want to go. I also show that it is possible to re-politicize the step of selection of the "portions of spaces" that will be included - or excluded - from zoning by basing it, more than it is done today, on the characteristics of the populations concerned, on a desire to articulate public policies and on the constraints that are imposed on zoning today to establish its potential effectiveness (acceptability by health professionals). My modeling also illustrates that proceeding by scenarios makes it possible to propose several possibilities of the reality of which we seek to produce a representation. This makes it possible to mobilize quantification as a tool of government and not as an idealized tool of proof, by testing - in a dispassionate manner - the geographical and population impact of different intention or political claim. Thus, my modeling shows, for example, that beyond moral questions, feasibility or induced risks, making zoning coercive rather than simply incentive could have few operational effects in Île-de-France, especially if the zoning is retained in its current contours.En France, comme ailleurs dans le monde, la lutte contre les difficultés d'accessibilité spatiale aux soins constitue depuis deux décennies un enjeu central et une priorité des politiques publiques de santé. Depuis 2005, la législation française prévoit que, dans chaque région, soient délimitées des zones considérées comme en déficit en matière d'offre médicale. Les médecins qui y exercent ou qui viennent s'y installer peuvent bénéficier d'un certain nombre d'aides publiques, l'objectif étant de favoriser une meilleure répartition géographique des professionnels de santé de ville. Face au constat d'efficacité limitée de cette politique publique, les mesures mises en œuvre sont régulièrement remises en cause de même que la méthodologie de délimitation du « zonage médecins ». Cette thèse est consacrée à questionner cette méthodologie de zonage. Un détour socio-historique préalable retraçant le processus de genèse de cet instrument d'action publique permet de comprendre que le zonage médecins actuel, dans sa forme purement incitative, est un outil de compromis façonné en partie par des enjeux pragmatiques dont il ne peut être fait abstraction. Je démontre ensuite pourquoi, en tant qu'instrument d'une politique publique de discrimination positive, les enjeux d'équité et de justice sociale et/ou spatiale s'imposent à l'instrument et j'explicite en quoi les méthodes de zonage actuelles sont largement conditionnées par un présupposé plus fantasmé qu'avéré d'un lien entre territoires en difficulté d'accessibilité spatiale aux médecins généralistes et territoires socialement défavorisés. A tel point que les méthodes de zonage actuelles reposent sur des critères sociaux autant que sur la mesure des niveaux d'accessibilité spatiale aux soins ce qui dénature la fonction même de ce zonage dont on ne sait plus s'il cible des territoires en difficulté d'accès aux soins ou bien s'il ne cible plus que des territoires en difficulté sociale. Dans cette thèse, je réintègre la dimension sociale des besoins au sein de la mesure des niveaux d'accessibilité spatiale aux médecins afin d'identifier, à partir du cas francilien, les territoires où les populations ont le plus de difficultés potentielles d'accessibilité spatiale aux médecins généralistes compte tenu de leurs caractéristiques sociales. J'explicite les choix sous-jacents de la méthode de mesure. En procédant par scénarios, je montre qu'en Île-de-France, la réalité représentée diffère très sensiblement selon les paramètres intégrés au modèle de mesure, soulignant ainsi l'importance à « repolitiser » la mesure (avant même l'étape de sélection) puisque les normes produites par les choix opérés dessinent implicitement (alors qu'ils devraient traduire explicitement) une vision spécifique de là où l'on souhaite aller. Je montre également qu'il est possible de repolitiser l'étape de sélection des « portions d'espaces » qui seront intégrées - ou exclues - du zonage en la fondant, plus que cela n'est fait aujourd'hui, sur les caractéristiques des populations concernées, sur une volonté d'articulation des différentes politiques publiques et sur les contraintes qui s'imposent aujourd'hui au zonage pour asseoir son efficacité potentielle (acceptabilité par les professionnels de santé). Mes modélisations illustrent également que procéder par scénarios permet de proposer plusieurs possibles de la réalité dont on cherche à produire une représentation. Cela permet de mobiliser la quantification bien comme un outil de gouvernement et non pas comme un outil de preuve idéalisé, en testant - de manière dépassionnée - l'impact géographique et populationnel de telle ou telle intention ou revendication politique. Ainsi, mes modélisations montrent par exemple, qu'au-delà des questions morales, de faisabilité ou de risques induits, rendre le zonage coercitif pourrait n'avoir que peu d'effets opérationnels en Île-de-France, surtout si le zonage est conservé dans ses contours actuels

Le zonage médecins en France : genèse d’un instrument d’action publique à dimension territoriale

En France, comme ailleurs, la lutte contre les difficultés d’accès aux soins constitue depuis plusieurs années une priorité des politiques publiques de santé. Depuis 2005, un « zonage médecins » réglementaire cible les territoires déficitaires en médecins généralistes, où les médecins sont éligibles à différentes aides publiques. Dans une approche socio-historique, cet article vise à décrire la genèse de cet instrument d’action publique et à en retracer le processus d’émergence lente et hésitante dans un paysage d’intérêts complexes et contradictoires. Dans un contexte de refonte du zonage médecins et de remise en question récurrente de sa pertinence, ce détour historique permet mieux comprendre que le zonage actuel, dans sa forme purement incitative, est un outil de compromis façonné en partie par des enjeux pragmatiques dont il ne peut être fait abstraction

Politiques de rationalisation de l’offre de soins et mobilité: Chapitre 7

International audienceLes politiques de rationalisation de l’offre de soins reposent largement sur la mesure de l’accessibilité spatiale aux soins. Cette dernière, au fil des évolutions méthodologiques et technologiques, considère de manière de plus en plus intégrée le concept de mobilité. Celui-ci reste néanmoins insuffisamment mobilisé pour questionner l’approche domo-centrée des mesures et tenir compte des différentiels sociaux de mobilité des populations