Search Publications
High-resolution Imaging of the Solar Chromosphere/Corona Transition Region
Schrijver, C. J.; De Pontieu, B.; Title, A. M. +1 more
The properties of a previously unresolved extreme-ultraviolet (EUV) emission in solar active regions are examined using coordinated data sets from the Transition Region and Coronal Explorer (TRACE) satellite, the Michelson Doppler Imager on the Solar and Heliospheric Observatory satellite, the Soft X-Ray Telescope (SXT) on the Yohkoh satellite, an…
Dispersal of Magnetic Flux in the Quiet Solar Photosphere
Schrijver, C. J.; Shine, R. A.; Title, A. M. +1 more
We study the random walk of magnetic flux concentrations on two sequences of high-resolution magnetograms, observed with the Michelson Doppler Imager on board SOHO. The flux contained in the concentrations ranges from |Φ|=1018 Mx to |Φ|=1019 Mx, with an average of |Φ|=2.5×1018 Mx. Larger concentrations tend to move…
HST/NICMOS2 observations of the HD 141569 A circumstellar disk
Ménard, F.; Mouillet, D.; Augereau, J. C. +1 more
We report the first resolved scattered light images of the circumstellar dust disk around the old Pre-Main Sequence star da. The disk seen in HST/NICMOS2 images shapes a bright annulus inclined at 37.5degr +/- 4.5degr from edge-on. This ring peaks at 325+/-10 AU from the star with a characteristic width of ~ 150 AU. At 1.6 mu m, the dust grains sc…
HUBBLE SPACE TELESCOPE Near-infrared and Optical Imaging of Faint Radio Sources in the Distant Cluster CL 0939+4713
Kneib, J. -P.; Ivison, R. J.; Morrison, G. +4 more
We present deep Hubble Space Telescope Near-Infrared Camera and Multiobject Spectrograph (NICMOS) and Wide Field and Planetary Camera 2 (WFPC2) optical imaging of a small region in the core of the distant rich cluster Cl 0939+4713 (z=0.41). We compare the optical and near-infrared morphologies of cluster members and find apparent small-scale optic…
EUV Spectral Line Profiles in Polar Coronal Holes from 1.3 to 3.0 Rsolar
Cranmer, S. R.; Fineschi, S.; Noci, G. +7 more
Spectral line profiles have been measured for H I λ1216, O VI λλ1032, 1037, and Mg X λ625 in a polar coronal hole observed during 1997 September 15-29, at projected heliographic heights ρ between 1.34 and 2.0 Rsolar. Observations of H I λ1216 and the O VI doublet from 1997 January for ρ=1.5-3.0 Rsolar are provided for compari…
Heating and cooling of protons by turbulence-driven ion cyclotron waves in the fast solar wind
Li, Xing; Habbal, Shadia R.; Hollweg, Joseph V. +1 more
The effects of parallel propagating nondispersive ion cyclotron waves on the solar wind plasma are investigated in an attempt to reproduce the observed proton temperature anisotropy, namely, Tp⊥>>Tp∥ in the inner corona and Tp⊥<Tp∥ at 1 AU. Low-frequency Alfvén waves are assumed to carry most of…
Galactic globular cluster stars: From theory to observation
Salaris, M.; Weiss, A.; Cassisi, S. +2 more
We use evolutionary calculations presented in a recent paper \cite[(Cassisi et al. 1997a:]{C97a} hereinafter Paper I) to predict B, V, I magnitudes for stars in galactic globulars. The effect of the adopted mixing length on stellar magnitudes and colors is discussed, showing that the uncertainty on such a theoretical parameter prevents the use of …
Three-dimensional propagation of coronal mass ejections in a structured solar wind flow 2. CME launched adjacent to the streamer belt
Pizzo, V. J.; Odstrčil, D.
A three-dimensional (3-D) numerical hydrodynamic model is used to investigate the evolution of coronal mass ejections (CMEs) launched at several heliographic positions into a tilted-dipole ambient solar wind (SW) flow, which is appropriate around solar activity minimum and declining phase. The CME is injected as an overpressured plasma cloud. Resu…
Hubble Space Telescope Photometry of the Fornax Dwarf Spheroidal Galaxy: Cluster 4 and Its Field
Castellani, M.; Marconi, G.; Buonanno, R. +3 more
Using observations from the Hubble Space Telescope archive, color-magnitude diagrams (CMDs) have been constructed for globular cluster 4 in the Fornax dwarf spheroidal galaxy and its surrounding field. These diagrams extend below the main-sequence turnoffs and have yielded measurements of the ages of the populations. The most prominent features of…
Photospheric Magnetic Reconnection and Canceling Magnetic Features on the Sun
Litvinenko, Yuri E.
Parameters describing quasi-steady reconnecting current sheets in the plasma of the solar photosphere and chromosphere are computed using the VAL-C atmospheric model. In particular, the inflow speed for the Sweet-Parker magnetic reconnection is found for a sheet whose width is determined by the density scale height. The resulting speed of several …