Analysis and interpretation of a fast limb CME with eruptive prominence, C-flare and EUV dimming

Coronal Mass ejections or CMEs are large dynamical solar-corona events. The mass balance and kinematics of a fast limb CME, including its prominence progenitor and the associated flare, will be compared with computed magnetic structures to look for their origin and effect. Multi-wavelength ground-based and space-borne observations are used to study a fast W-limb CME event of December 2, 2003, taking into account both on and off disk observations. Its erupting prominence is measured at high cadence with the Pic du Midi full H-alpha line-flux imaging coronagraph. EUV images from space instruments are processed including difference imaging. SOHO/LASCO images are used to study the mass excess and motions. A fast bright expanding coronal loop is identified in the region recorded slightly later by GOES as a C7.2 flare, followed by a brightening and an acceleration phase of the erupting material with both cool and hot components. The total coronal radiative flux dropped by 5 percent in the EUV channels, revealing a large dimming effect at and above the limb. The typical 3-part structure observed 1 hour later shows a core shaped similarly to the eruptive filament/prominence. The total measured mass of the escaping CME (1.5x10to16 g from C2 LASCO observations) definitely exceeds the estimated mass of the escaping cool prominence material although assumptions made to analyse the Ha erupting prominence, as well as the corresponding EUV darkening of the filament observed several days before, made this evaluation uncertain by a factor of 2. From the current free extrapolation we discuss the shape of the magnetic neutral surface and a possible scenario leading to an instability, including the small scale dynamics inside and around the filament.Comment: 11 pages, 9 figure

Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution

The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201

Three-Dimensional Views of the Nucleus of Comet 67P/Churyumov-Gerasimenko - Application to the Characterization of Active Pits

International audienceThe Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired approximately 25000 images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at various spatial scales down to centimeters per pixel. The bulk of these images have been obtained in sequences and the combined displacement of the Rosetta orbiter along its trajectory and the rotation of the nucleus allow associating many pairs of images appropriate to stereoscopic viewing. This is achieved by constructing anaglyphs after rotating the images so that the relative shift appears horizontal. The shift is set to limit the parallax to approximately 2° (with a maximum value of 4°) for the foreground so as to avoid image deformation. A time of writing, approximately 1100 anaglyphs have been produced. In addition to offering spectacular stereoscopic views of the nucleus, these anaglyphs allow studying the topography of the nucleus at spatial scales unachievable by DTMs. Further coupling with spectral images, we have been able to locate ice patches at the bottom of several narrow pits which indicate the presence of sub-surface ice at depths of a few meters. These narrow pits are most likely the sources of collimated jets widely seen in the coma of 67PC-G

A catalog of stereo anaglyphs of comet 67P/Churyumov- Gerasimenko - Application to the detection of deep ice pits

International audienceThe OSIRIS/NAC camera aboard the Rosetta spacecraft has acquired approximately 27000 images of comet 67P/Churyumov-Gerasimenko at spatial scales down to a few centimeters. We exploit the numerous sequences of images separated by a few minutes suitable for stereo reconstructions to produce anaglyphs offering three-dimensional views of the comet, complementary to other technics, as a tool to understand the topography of the nucleus. Each anaglyph is documented by a set of 17 parameters which provide the contextual information. Over 1400 anaglyphs have been produced and cataloged so far; they are available on a dedicated website and can be searched using the associated parameters. As a first application, we present direct evidences of sub-surface ice at the bottom of deep pits, so-called "ice pits" identified on high-resolution anaglyphs. Their geometry and size are obtained from stereographic reconstruction. Both their high reflectivity and their blue color substantiate the presence of ice

Homogenization of Composite Panels from a Near-Field Magnetic Shielding Effectiveness Measurement

International audienceA simple method permitting to obtain a homogeneous panel from a strongly inhomogeneous panel is presented. The method consists of determining the characteristics of a panel having an equivalent conductivity obtained from a near-field magnetic shielding effectiveness measurement. Thus, the method suitable for frequencies lower than 1 MHz does not require the knowledge of the detailed internal geometry of the sample. After the validation of the measurement setup on a copper plate of known conductivity, two space composite panels are characterized and homogenized

Analysis of broad-band H

Context.Daily broad-band full-limb Hα images of the inner corona were obtained during solar cycle 23 (1994–2005) using the 15 cm Pic-du-Midi coronagraph. Aims.We want to automatically extract the properties and evolutions of the observed cool HI coronal structures over a wide range of sizes and light fluxes, from small jets and/or spikes to large prominences. Methods.A tool was developed to process the complete set of stored images. This paper describes the recognition techniques implemented in our software and discusses its use. It includes the removal of the parasitic diffraction ring produced by the set of different occulting disks used throughout the year. Results.We present and discuss selected results from a statistical analysis of the occurrence of parameters characterizing the observed structures applied to a large sample of observations. It illustrates the capabilities of this software when applied to our database. Strong asymmetries of the activity level over the solar poles become evident, confirming similar results from previous works. We also discuss the distribution of relative light fluxes of these structures over a wide range of sizes. Conclusions.The complete series of FITS and calibrated images, the list of the detected structures, and their geometric and luminosity evolutions are stored in the BASS2000 solar database catalogue (http://bass2000.bagn.obs-mip.f

Améliorations de la méthodologie permettant le calcul du rayonnement électromagnétique parasite d'un panneau solaire réaliste

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Détermination du modèle électrique équivalent d'un panneau composite

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