Proper orthogonal decomposition of solar photospheric motions

The spatio-temporal dynamics of the solar photosphere is studied by performing a Proper Orthogonal Decomposition (POD) of line of sight velocity fields computed from high resolution data coming from the MDI/SOHO instrument. Using this technique, we are able to identify and characterize the different dynamical regimes acting in the system. Low frequency oscillations, with frequencies in the range 20-130 microHz, dominate the most energetic POD modes (excluding solar rotation), and are characterized by spatial patterns with typical scales of about 3 Mm. Patterns with larger typical scales of 10 Mm, are associated to p-modes oscillations at frequencies of about 3000 microHz.Comment: 8 figures in jpg in press on PR

On Landau damping

Going beyond the linearized study has been a longstanding problem in the theory of Landau damping. In this paper we establish exponential Landau damping in analytic regularity. The damping phenomenon is reinterpreted in terms of transfer of regularity between kinetic and spatial variables, rather than exchanges of energy; phase mixing is the driving mechanism. The analysis involves new families of analytic norms, measuring regularity by comparison with solutions of the free transport equation; new functional inequalities; a control of nonlinear echoes; sharp scattering estimates; and a Newton approximation scheme. Our results hold for any potential no more singular than Coulomb or Newton interaction; the limit cases are included with specific technical effort. As a side result, the stability of homogeneous equilibria of the nonlinear Vlasov equation is established under sharp assumptions. We point out the strong analogy with the KAM theory, and discuss physical implications.Comment: News: (1) the main result now covers Coulomb and Newton potentials, and (2) some classes of Gevrey data; (3) as a corollary this implies new results of stability of homogeneous nonmonotone equilibria for the gravitational Vlasov-Poisson equatio

Concentration urbaine des spores dans les pays de la Communauté Économique Européenne. III. - Les urticacées

The authors report, here, a comparative study of Urticaceae pollen rains in the European Economic Community. This family takes a great part in the annuel amount of pollen grains in the five countries of the E.E.C. but, its clinical influence seems to be minor, except in the Mediterranean area of France, where Parietaria is responsible of many cases of asthma. © 1977 Expansion Scientifique Française.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

SPORENKONZENTRATIONEN IN STÄDTEN DER EUROPÄISCHEN GEMEINSCHAFT (EG): II. Cladosporium‐ und Alternaria‐Sporen

SCOPUS: ar.jinfo:eu-repo/semantics/publishe