Search Publications
Cluster observations and theoretical identification of broadband waves in the auroral region
André, M.; Stenberg, G.; Rème, H. +7 more
Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to t…
Solar cycle evolution of the contrast of small photospheric magnetic elements
Ortiz, Ada
Solar irradiance variations produced on the solar rotation time-scale are known to be driven by the passage of active regions while, during the last years, the origin of variations on the solar cycle time-scale has been under debate. Nowadays, there is an agreement that the magnetic network has an important contribution to these long-term variatio…
Metallicity of mono- and multiperiodic β Cephei stars
Niemczura, E.; Daszyńska-Daszkiewicz, J.
Analyzing IUE ultraviolet spectra of β Cep pulsating stars we noticed that multiperiodic variables have a larger mean metal abundance in the photosphere, [ m/H] , than monoperiodic ones. We apply statistical tests to verify this dichotomy. We obtain that, with a large probability, the multiperiodic β Cep stars have greater values of [ m/H] . This …
A solar active region loop compared with a 2D MHD model
Gontikakis, C.; Tsinganos, K.; Petrie, G. J. D. +1 more
We analyzed a coronal loop observed with the Normal Incidence Spectrometer (NIS), which is part of the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO). The measured Doppler shifts and proper motions along the selected loop strongly indicate unidirectional flows. Analysing the Emission Measure Curves of …
The First Optical Validation of an X-Ray Line-emitting Object: A Detection in the XMM-Newton Observation of the Chandra Deep Field-South
Braito, V.; Caccianiga, A.; Severgnini, P. +2 more
We present the first optical validation of an X-ray line-emitting object (XLEO) discovered in the XMM-Newton observation of the Chandra Deep Field-South. The object is an active galactic nucleus at zX~0.66. An optical spectrum of the source indeed confirms and refines (zo=0.665) the redshift obtained from the X-ray line. The …
The HST Cosmos Project: Contribution from the SUBARU Telescope
Aussel, H.; Sanders, D. B.; Murayama, T. +16 more
The Cosmic Evolution Survey (COSMOS) is a Hubble Space Telescope (HST) treasury project.The COSMOS aims to perform a 2 square degree imaging survey of an equatorial field in $I$(F814W) band, using the Advanced Camera for Surveys (ACS). Such a wide field survey, combined with ground-based photometric and spectroscopic data, is essential to understa…
Evolution of Barb Angle and Filament Eruption
Liu, Y.; Li, C.; Zhang, H. Q. +6 more
Hα observations of a quiescent U-shaped filament were obtained at Big Bear Solar Observatory and at Hida Observatory with the Flare Monitoring Telescope. The filament was located in the southern hemisphere on 1998 November 4. We study the evolution of the angle of a barb with respect to the axis of the filament and find the evolution can be divide…
Pre-Main Sequence Stars Seen by ISO
Lorenzetti, Dario
Observations of pre-main sequence objects (T Tauri, Herbig Ae/Be and FU Orionis stars) obtained with the instrumentation on board the Infrared Space Observatory (ISO) are reviewed. All the observations have been mainly carried out by using the two spectrographs SWS and LWS, adopting their low resolution modes and such data have been used both for …
Temporal variations in the magnetic network large-scale dynamics
Meunier, N.
The variation in the magnetic network large-scale dynamics is investigated using MDI magnetograms from 1996 to 2004. Cross-correlation and feature tracking techniques are used on pairs of magnetograms in order to derive the dynamics at the solar surface, including magnetic network regions. The variations for both methods are very different, the fe…
The extent of 3-min oscillations in regions other than sunspot plumes
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
The active region, AR0554, was observed with NIS/CDS on board SoHO to examine the extent and range of oscillations from a range of features. Among all the NIS spectral lines analysed, significant oscillations were found in Si xii 520 Å, Mg x 625 Å, O v 629 Å, and He i 522 Å. The periods of the strongest oscillations in these lines were ≈10-20 min.…