Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

The use of neutral and non-neutral SSRs to analyse the genetic structure of a Tunisian collection of Medicago truncatula lines and to reveal associations with eco-environmental variables

Contact :[email protected] audienceIn this study, we investigated the genetic diversity of a collection of 136 Medicago truncatula lines from 10 Tunisian natural populations collected in well-defined locations and in various ecological conditions of soil, salinity and water availability. The genetic diversity was evaluated using a set of 18 microsatellites (SSRs), representing the 8 chromosomes of M. truncatula. A neutrality test showed that 7 SSRs were non-neutral with evidence of balancing selection. The 11 neutral SSRs revealed a geographical pooling with the Tunisian Dorsale axis restricting migration of alleles. The 7 non-neutral alleles demonstrate a correlation with rainfall, altitude and salinity environmental variables suggesting that these SSRs are linked to genes involved in water use efficiency, resistance to salinity or adaptation to altitude, and that there is local adaptation of M. truncatula to these variables. This demonstrates that the choice of so-called neutral markers should be carefully evaluated in population genetic studies. This study illustrates the genetic diversity occurring in natural Tunisian populations of M. truncatula and describes the first collection of this species dedicated to natural variation involved in adaptation to the environmen

The first optical characterization of the Oukaïmeden site with the Generalized Seeing Monitor (GSM)

The main atmospheric optical parameters (AOP) have been measured during 10 nights in April 1998 with the GSM instrument at the Moroccan site of Oukaïmeden. These parameters are of interest for the optimization of high angular resolution techniques. During this campaign the temporal evolution of the AOP and their distributions have been studied. The outer scale presents a log-normal histogram with a median value of 31 m which is rather similar to the values obtained at other sites visited with GSM. The selection of the Oukaïmeden site is the result of several topographical and meteorological studies on the Atlas mountain chain. Since 1988 this site has been chosen for the installation of one of the IRIS (International Research of the Interior of the Sun) stations. Here, we present the whole AOP data measured with GSM during this campaign. The main photometric and meteorological conditions of this site are also presented

THE SOLAR ACOUSTIC SPECTRUM AS SEEN BY GOLF. III. ASYMMETRIES, RESONANT FREQUENCIES AND SPLITTINGS T. Roca Cort'es

The definition of the model to fit to the observed spectra depends on the physics we are assuming is present in the phenomena we are observing. Here we present the results obtained following the fit of several models (described in poster GOLF.II, Roca Cort'es et al.). Therefore the effects of asymmetrical line shapes, a common background for all modes, fixed relative power in the components of a multiplet and a constant splitting between the components of each multiplet on the resonant frequencies (and their errors) of the modes will be evaluated. Finally, a table of frequencies and splittings will be given. Key words: helioseismology; low degreemodes; frequencies; splittings. 1. INTRODUCTION The data displayed in this work has been achieved after the analysis of two series mainly, one with ß14 months of data and a second one with ß21 months of GOLF data with the methods and strategy fits described in more detail in poster GOLF.II and summarized here: ffl AvFFT. Average of FFT of subse..

First statistics of the isopistonic angle for long baseline interferometry

International audienceTo reach a suitable limiting magnitude with a multi-aperture interferometer, we need tocophase the different telescopes using a reference source. The latter should be located in thesame isopistonic domain as the science source. We developed a direct analytical expressionof deducing the isopistonic angle from atmospheric optical parameters as seeing, isoplanaticangle and outer scale. All of these atmospheric turbulence parameters are measured by theGeneralized Seeing Monitor (GSM). The first statistics of the isopistonic angle obtained fromthe GSM data are presented and comparison between the major sites over the world arediscussed (La Silla, Cerro Pachon, Paranal, San Pedro, Mt Palomar, Mauna Kea, La Palma,Ouka ̈ımeden, Maydanak, Dome C). Implications of these isopistonic angle statistics on largeinterferometers cophasing in terms of sky coverage and limiting magnitude are discussed

Solar

With the GOLF instrument onboard the SoHO observatory, 1979 days of full-disc Doppler velocity observations have been compiled into a study of p-mode properties. We develop a multi-step iterative method (MSIM) algorithm to access all p-mode parameters while minimizing any perturbating effect or cross-talk between parameters during their determination. We present frequency and splitting tables, amplitudes, linewidths, line asymmetries, pseudo-modes, and background noise determinations. We have a first look at the changes induced by the transition from the low-activity to the high-activity part of solar cycle 23: we have recorded frequency shifts with a downturn at 3.7 mHz followed by a possible higher upturn, and linewidth changes to a good accuracy. We detect an effect on the noise background at 3 mHz possibly related to an interaction between noise and the modes and connected to the asymmetry of the profiles