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Alpha/proton magnetosonic instability in the solar wind
Gary, S. Peter; Winske, Dan; Reisenfeld, Daniel B. +1 more
The average relative flow velocity between protons and alpha particles in collisionless plasmas can excite several distinct alpha/proton instabilities. Here linear theory and two-dimensional hybrid simulations in a homogeneous plasma model are used to study one such mode, the alpha/proton magnetosonic instability, using plasma parameters character…
The Hubble Space Telescope Survey of BL Lacertae Objects. III. Morphological Properties of Low-Redshift Host Galaxies
Urry, C. Megan; Scarpa, Riccardo; Treves, Aldo +1 more
We report on the optical properties of a sample of 30 BL Lac host galaxies in the redshift range 0.03<z<0.2, as derived from Hubble Space Telescope observations. All galaxies are fully resolved in the WFPC2 (F702W filter) images, allowing a quantitative analysis in two dimensions. Most and possibly all of these galaxies have characteristics …
Space Telescope Imaging Spectrograph Long-Slit Spectroscopy of the Narrow-Line Region of NGC 4151. I. Kinematics and Emission-Line Ratios
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +5 more
Long-slit spectra of the Seyfert galaxy NGC 4151 from the UV to the near-infrared have been obtained with the Space Telescope Imaging Spectrograph (STIS) to study the kinematics and physical conditions in the narrow-line region (NLR). The kinematics shows evidence for three components, a low-velocity system in normal disk rotation, a high-velocity…
Molecular Gas Properties of the Starburst Nucleus of IC 342: High-Resolution 13CO (2-1) Imaging
Meier, David S.; Turner, Jean L.; Hurt, Robert L.
We present a map of the J=2-1 transition of 13CO in the starburst nucleus of IC 342 made with the Owens Valley Millimeter Array. The interferometric 13CO map allows us to directly compare with 12CO (1-0), 12CO (2-1), and 13CO (1-0) maps of nearly identical (~4.5") resolution. While all four tr…
Theoretical models for classical Cepheids. VII. Metallicity effects on the Cepheid distance scale
Marconi, M.; Musella, I.; Caputo, F. +1 more
We use theoretical Period-Luminosity and Period-Luminosity-Color relations in the VI passbands, as based on nonlinear, nonlocal and time-dependent convective pulsating models, to predict the reddening and true distance modulus of distant Cepheids observed with the Hubble Space Telescope. By relying on the pulsating models with metal content Z=0.00…
Elementary heating events - Magnetic interactions between two flux sources
Parnell, C. E.; Galsgaard, K.; Blaizot, J.
Observations taken by the SoHO MDI instrument have revealed that the quiet photospheric magnetic flux is, on average, recycled within a few days. As new flux emerges from the convection zone into the photosphere it is moved around by horizontal motions resulting from overshoots of convection cells. These motions cause the magnetic fields extending…
η Carinae: Testing a Binary Orbit Model with the Hubble Space Telescope/Space Telescope Imaging Spectrograph
Smith, Nathan; Gull, Theodore R.; Humphreys, Roberta M. +2 more
Ground-based spectroscopy of η Car shows periodic changes in some emission-line wavelengths. These variations have been cited as strong evidence that this object is a 5.5 yr binary system and have been used to produce specific orbit models. High spatial resolution data obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph, …
Ulysses observations of the irregularly structured mid-latitude solar wind during the approach to solar maximum
McComas, D. J.; Gosling, J. T.; Skoug, R. M.
The Ulysses spacecraft reached 45°S heliolatitude in its second polar orbit on 5 February 2000. Solar wind observations over the first portion of Ulysses' second orbit have been remarkably different from those taken at mid-latitudes throughout its first orbit. During these portions of its first orbit, Ulysses crossed back and forth between the fas…
Detection of mid-infrared aromatic hydrocarbon emission features from the Small Magellanic Cloud
Boulanger, F.; Reach, W. T.; Contursi, A. +1 more
The mid-infrared (5-16 mu m) spectral energy distribution for an individual quiescent molecular cloud in the Small Magellanic Cloud (SMC) was observed using ISOCAM. The spectrum is dominated by broad emission bands at 6.2, 7.7, and 11.3 mu m, with weaker bands at 8.6 and 12.7 mu m. As these are the same bands, with similar shape and relative stren…
Magnetic structure of overexpanding coronal mass ejections: Numerical models
Cargill, Peter J.; Schmidt, Joachim; Spicer, D. S. +1 more
Numerical simulations are presented of the evolution of overexpanding coronal mass ejections (OCMEs), which are also magnetic clouds. The OCME is assumed to arise from the evolution of a magnetic flux rope with high plasma and magnetic pressure and high plasma density near the Sun in a high-speed solar wind. It is shown that the flux rope maintain…