Classifications of elliptic fibrations of a singular K3 surface

We classify, up to automorphisms, the elliptic fibrations on the singular K3 surface $X$ whose transcendental lattice is isometric to $\langle 6\rangle\oplus \langle 2\rangle$.Comment: 28 page

Understanding CME and associated shock in the solar corona by merging multi wavelengths observation

Using multi-wavelength imaging observations, in EUV, white light and radio, and radio spectral data over a large frequency range, we analyzed the triggering and development of a complex eruptive event. This one includes two components, an eruptive jet and a CME which interact during more than 30 min, and can be considered as physically linked. This was an unusual event. The jet is generated above a typical complex magnetic configuration which has been investigated in many former studies related to the build-up of eruptive jets; this configuration includes fan-field lines originating from a corona null point above a parasitic polarity, which is embedded in one polarity region of large Active Region (AR). The initiation and development of the CME, observed first in EUV, does not show usual signatures. In this case, the eruptive jet is the main actor of this event. The CME appears first as a simple loop system which becomes destabilized by magnetic reconnection between the outer part of the jet and the ambient medium. The progression of the CME is closely associated with the occurrence of two successive types II bursts from distinct origin. An important part of this study is the first radio type II burst for which the joint spectral and imaging observations allowed: i) to follow, step by step, the evolution of the spectrum and of the trajectory of the radio burst, in relationship with the CME evolution; ii) to obtain, without introducing an electronic density model, the B-field and the Alfven speed.Comment: 17 pages, 13 figure

Radio Jupiter after Voyager: An overview of the Planetary Radio Astronomy observations

Jupiter's low frequency radio emission morphology as observed by the Planetary Radio Astronomy (PRA) instrument onboard the Voyager spacecraft is reviewed. The PRA measurement capabilities and limitations are summarized following over two years of experience with the instrument. As a direct consequence of the PRA spacecraft observations, unprecedented in terms of their sensitivity and frequency coverage, at least three previous unrecognized emission components were discovered: broadband and narrow band kilometric emission and the lesser arc decametric emission. Their properties are reviewed. In addition, the fundamental structure of the decameter and hectometer wavelength emission, which is believed to be almost exclusively in the form of complex but repeating arc structures in the frequency time domain, is described. Dramatic changes in the emission morphology of some components as a function of Sun-Jupiter-spacecraft angle (local time) are described. Finally, the PRA in suit measurements of the Io plasma torus hot to cold electron density and temperature ratios are summarized

Voyager spacecraft radio observations of Jupiter: Initial cruise results

Jupiter's low-frequency radio emission were detected by the planetary radio astronomy instruments onboard the two Voyager spacecraft. The emission is surprisingly similar in morphology but opposite in polarization to the high-frequency Jovian radio noise that were observed with ground-based telescopes for more than two decades. Several possible explanations for the behavior of the low-frequency emission are examined, but none of them is completely satisfactory

Reply to comment by B. Cecconi on "Spectral features of SKR observed by Cassini/RPWS: Frequency bandwidth, flux density and polarization"

International audienceThe main purpose of the paper by Galopeau et al.[2007] was to classify the spectral features of the Saturniankilometric radiation (SKR) starting from three physicalobserved parameters: the frequency bandwidth, the fluxdensity, and the pol arization. We show in the presentresponse that an unsupervised application of arbitrary auto-matic criteria during the data processing (such as a signal-to-noise ratio greater than 23 dB) can totally judge a weaknatural emission as a background noise. As a consequence,such a situation may lead to consideration of only the datapresenting a degree of circular polarization close to 100%and neglect a huge part of the data. Galopeau et al. [2007]considered a phenomenological aspect and gave an estima-tion of the Stokes parameters. This approach leads to firstrecognizing spectral components (flux density and band-width) in the frequency range from 3.5 kHz to 1200 kHz,and then deriving the Stokes parameters for each compo-nent. The Cassini/RPWS instrument provides long-lastingcoverage of radio emissions at Saturn with unprecedentedinstrumental capabilities

In-flight calibration of STEREO-B/WAVES antenna system

The STEREO/WAVES (SWAVES) experiment on board the two STEREO spacecraft (Solar Terrestrial Relations Observatory) launched on 25 October 2006 is dedicated to the measurement of the radio spectrum at frequencies between a few kilohertz and 16 MHz. The SWAVES antenna system consists of 6 m long orthogonal monopoles designed to measure the electric component of the radio waves. With this configuration direction finding of radio sources and polarimetry (analysis of the polarization state) of incident radio waves is possible. For the evaluation of the SWAVES data the receiving properties of the antennas, distorted by the radiation coupling with the spacecraft body and other onboard devices, have to be known accurately. In the present context, these properties are described by the antenna effective length vectors. We present the results of an in-flight calibration of the SWAVES antennas using the observations of the nonthermal terrestrial auroral kilometric radiation (AKR) during STEREO roll maneuvers in an early stage of the mission. A least squares method combined with a genetic algorithm was applied to find the effective length vectors of the STEREO Behind (STEREO-B)/WAVES antennas in a quasi-static frequency range ($L_{antenna} \ll \lambda_{wave}$) which fit best to the model and observed AKR intensity profiles. The obtained results confirm the former SWAVES antenna analysis by rheometry and numerical simulations. A final set of antenna parameters is recommended as a basis for evaluations of the SWAVES data