Search Publications
Cassini CIRS retrievals of ammonia in Jupiter's upper troposphere
Achterberg, Richard K.; Conrath, Barney J.; Gierasch, Peter J.
The zonal mean ammonia abundance on Jupiter between the 400- and 500-mbar pressure levels is inferred as a function of latitude from Cassini Composite Infrared Spectrometer data. Near the Great Red Spot, the ammonia abundance is mapped as a function of latitude and longitude. The Equatorial Zone is rich in ammonia, with a relative humidity near un…
What is the spatial distribution of magnetic helicity injected in a solar active region?
Démoulin, P.; Pariat, E.; Nindos, A. +1 more
Context: .Magnetic helicity is suspected to play a key role in solar phenomena such as flares and coronal mass ejections. Several investigations have recently computed the photospheric flux of magnetic helicity in active regions. The derived spatial maps of the helicity flux density, called G_A, have an intrinsic mixed-sign patchy distribution.
Dynamical Evolution of the TW Hydrae Association
Ortega, V. G.; de la Reza, R.; Jilinski, E.
Using Galactic dynamics we have determined the age of the low-mass post-T Tauri stars in the TW Hya Association (TWA). To do so we applied the method of Ortega and coworkers to five stars of the association with Hipparcos-measured distances (TWA 1, TWA 4, TWA 9, TWA 11, and TWA 19). The method is based on the calculation of the past three-dimensio…
Seismic Emission from A M9.5-Class Solar Flare
Cally, P. S.; Lindsey, C.; Donea, A. -C. +2 more
Following the discovery of a few significant seismic sources at 6.0 mHz from the large solar flares of October 28 and 29, 2003, we have extended SOHO/MDI helioseismic observations to moderate M-class flares. We report the detection of seismic waves emitted from the β γ δ active region NOAA 9608 on September 9, 2001. A quite impulsive solar flare o…
Microquasars as sources of positron annihilation radiation
Guessoum, N.; Jean, P.; Prantzos, N.
We consider the production of positrons in microquasars, i.e. X-ray binary systems that exhibit jets frequently, but not continuously. We estimate the production rate of positrons in microquasars, both by simple energy considerations and in the framework of various proposed models. We then evaluate the collective emissivity of the annihilation rad…
Morphology of the ultraviolet Io footprint emission and its control by Io's location
Clarke, John T.; Grodent, Denis; GéRard, Jean-Claude +1 more
A total of 74 images of the ultraviolet footprint of the Io flux tube (IFT) on Jupiter's upper atmosphere made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope have been analyzed to characterize their location, morphology, and brightness distribution. The observations cover a wide range of central meridian Jovian l…
Enceladus: A significant plasma source for Saturn's magnetosphere
Hill, T. W.; Pontius, D. H.
The Cassini Plasma Spectrometer has reported dramatic perturbations of the magnetospheric plasma flow in a region extending at least 30 satellite radii away from Saturn's small but active icy satellite Enceladus. We interpret these observations here by means of a steady state model of the electrodynamic coupling between Enceladus and Saturn. Neutr…
Ulysses observations of very different heliospheric structure during the declining phase of solar activity cycle 23
McComas, D. J.; Gosling, J. T.; Elliott, H. A. +1 more
This study examines the most recent observations from the solar wind experiment (SWOOPS) on the Ulysses spacecraft. In contrast to observations over the same locations in the declining phase of the previous solar activity cycle, these data show a more complicated heliospheric structure. Around the start of 2003, a band of slow solar wind resided a…
The clustering evolution of distant red galaxies in the GOODS-MUSIC sample
Fontana, A.; Vanzella, E.; Grazian, A. +8 more
Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies.
Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~µm) and …
Measuring supermassive black holes with gas kinematics: the active S0 galaxy NGC 3998
Marconi, A.; Capetti, A.; de Francesco, G.
Context: .We present results from a kinematical study of the gas in the nucleus of the active S0 galaxy NGC 3998 obtained from archival HST/STIS long-slit spectra.
Aims: .We analyzed the emission lines profiles and derived the map of the gas velocity field. The observed velocity curves are consistent with gas in regular rotation around the gal…