Search Publications
Characterization of Solar Coronal Holes and Plumes Using Spectroscopic Diagnostic Techniques Applied to SOHO/CDS Observations
Del Zanna, G.; Bromage, B. J. I.
Results from a series of SOHO/Coronal Diagnostic Spectrometer (CDS) observations of coronal holes and plumes are presented, including analysis of a low-latitude plume observed in August 1996. Spectroscopic diagnostic techniques using the CHIANTI atomic database are applied to derive the plasma parameters: electron density, temperature, and element…
Interacting and Interplanetary Protons Accelerated on Diverging Magnetic Field Lines: Stochastic Acceleration
Laitinen, T.; Torsti, J.; Mäkelä, P. +2 more
We study the ratio of the numbers of interplanetary to interacting protons, Γ, using a model of stochastic acceleration on open magnetic field lines in solar corona. The impact of diverging coronal magnetic field lines is incorporated into the particle transport operator and shown to be unavoidable, no matter how small the mean free path may be. W…
Implications of the heliospheric modulation of cosmic ray electrons observed by ulysses
Ferreira, S. E. S.; Potgieter, M. S.; Heber, B. +2 more
The results of a moderate drift model with anisotropic perpendicular diffusion for the heliospheric modulation of galactic cosmic rays were compared with electron spectra observed by the Kiel Electron Telescope on board the Ulysses spacecraft for four distinctive periods, 1992, 1995, 1996, and 1997, respectively, for relative large solar activity …
Hubble Space Telescope Faint Object Spectrograph Observations of a Unique Grouping of Five QSOs: The Sizes and Shapes of Low-z Lyα Forest Absorbers
Turnshek, David A.; Monier, Eric M.; Hazard, Cyril
Observations of QSO pairs suggest that the structures responsible for Lyα forest absorption lines must have radii of hundreds of kiloparsecs if they are spherical or disklike in shape. However, only observations of groups of three or more QSOs closely spaced on the sky provide a way to measure their transverse sizes/characteristic clustering lengt…
The correspondence of EUV and white light observations of coronal mass ejections with SOHO EIT and LASCO
St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J. +6 more
For over two years of operation, the LASCO coronagraph and the EIT imaging telescope have conducted observing campaigns intending to provide continuous coverage of global coronal dynamic phemonena. These compatible observations, which we call the "CME Watch," have been used to further our understanding of CME initiation and propagation, and to pro…
Sputtering efficiency of LiF surfaces on impact of low energy neutral helium (20-80 eV): Calibration of the interstellar neutral helium instrument on ULYSSES
Rosenbauer, H.; Witte, M.; Banaszkiewicz, M. +1 more
For the detection of interstellar neutral helium particles entering the inner solar system, a novel detection technique has been developed using sputtering of secondary ions from lithium-fluoride (LiF) surfaces on the impact of He particles. In order to be able to determine the interstellar He fluxes, the detection efficiency had to be determined …
Hubble Space Telescope NICMOS Observations of Rest-Frame Optical Continuum and Hα+[N I] Emission In FSC 10214+4724
Armus, L.; Scoville, N. Z.; Soifer, B. T. +4 more
High-resolution 1.10, 2.05, 2.12, and 2.15 µm imaging of the gravitationally lensed system FSC 10214+4724 are presented. These data extend Hubble Space Telescope (HST) observations of the lens system to redder wavelengths, thus providing the highest resolution images to date of the rest-frame optical and narrow-line (i.e., Hα+[N II]) regions…
Compact Nuclei in Galaxies at Moderate Redshift. I. Imaging and Spectroscopy
Green, Richard F.; Griffiths, Richard E.; Ratnatunga, Kavan +1 more
This study explores the space density and properties of active galaxies to z~=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as active galactic nuclei (AGNs) or starbursts. Candidates are selected by fitting imaged galaxies with multicomponent models u…
Absorption/Emission of Solar p-Modes: Michelson Doppler Interferometer/SOHO Observations
Zweibel, Ellen G.; Jain, Rekha; Haber, Deborah
We search for sources and sinks of solar p-mode waves by creating absorption maps from Dopplergrams taken by the Michelson Doppler Interferometer instrument on board SOHO. Although the maps are noisy, we present evidence for sources and sinks, of duration ~0.5-1 hour or less, based on an autocorrelation analysis of maps made from sequential interv…
Disk Winds of B[e] Supergiants
Zickgraf, Franz-Josef
The class of B[e] supegiants is characterized by a two-component stellar wind consisting of a normal hot star wind in the polar zone and a slow and dense disk-like wind in the equatorial region. The properties of the disk wind are discussed using satellite UV spectra of stars seen edge-on, i.e. through the equatorial disk. These observations show …