Dynamics of the Nuclear Outflow in NGC 1068

A short survey is presented of dynamical (and thermodynamical) issues relevant to outflows in Seyfert galaxies like NGC 1068. Numerical simulations incorporating both realistic radiative heating and cooling, and angular momentum, show that the fraction of injected gas which escapes in a wind is very sensitive to both the injection pressure and the gas's angular momentum. Radiation pressure acting through a variety of atomic opacity processes may also be important. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectral Study of Ionized Xenon Using a Capillary Pulsed Discharge

This work presents preliminaries spectroscopic results about ionized xenon and xenon-helium mixture using a capillary pulsed discharge under several experimental results.     

Near-Infrared Imaging Spectrophotometry Of Comet C/1995 O1 (Hale-Bopp) Near Perihelion

We present 1- to 5-μm broadband and CVF images of comet Hale-Bopp taken 1997 February 10.5 UT, 50 days before perihelion. All the images exhibit a nonspherical coma with a bright “ridge” in the direction of the dust tail approximately 10″ from the coma. Synthetic aperture spectrophotometry implies that the optically important grains are of a radius ≤0.4 μm; smallest radius for any comet seen to date. The variation of the integrated surface brightness with radial distance from the coma (ρ) in all the images closely follows the “steady state” ρ⁻¹ model for comet dust ablation (Gehrz and Ney, 1992). The near-infrared colors taken along the dust tail are not constant implying the dust grain properties vary with coma distance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of a Wavefront Sensing Concept for a Full Solar Disk Adaptive Optics System

Solar scintillations were investigated as a method of detecting seeing-dependent wavefront curvature variations for solar adaptive optics. The method is applicable to full-disk averaged, adaptive corrections of large-scale near-field seeing distortions. As a test case, seeing measurements were carried out on a single small adaptive mirror, representing one element of what would be a large multielement adaptive array. All observations showed a greater than 5× reduction of seeing distortions as a result of this wavefront correction.     

Magnetic field and differential rotation in the radiative zone of the Sun

The problem of the interaction between magnetic fields and differential rotation in the radiative zone of the Sun is investigated. It is demonstrated that effects of magnetic buoyancy can be neglected in the analysis of this interaction. It is shown that hydromagnetic torsional waves propagating from the solar core cannot be responsible for the 22-year solar cycle. A possible geometry of the magnetic field that conforms with stationary differential rotation is considered. A verifying method for hypotheses on the structure of the magnetic field and torsional oscillations in the radiative zone of the Sun is proposed based on helioseismic data.     

Arbitrary amplitude double layers in a multi-species electron-positron plasma

The existence and properties of arbitrary amplitude double layers in a four-component electron-positron plasma, consisting of two species of hot electrons, a hot and a cold positron species, are investigated as functions of plasma properties such as density and temperature ratios. Their behaviour for other plasma models is also discussed. Applications to the polar-cusp region of pulsars is considered.     

The Chromospheric Radiation on the Circumstellar Shell of Tx Piscium

Using the chromospheric UV flux based on IUE data, we have undertaken a wavelength calculation of the rates of photodissociation and the a abundances of the relevant molecules CO, SiS, HCN and C₂H₂ for the inner region of the circumstellar shell of the carbon-rich star TX Psc. Shielding by heavy elements and dust was taken into account. Further, for CO, the line self-shielding as an additional shielding process was included. We find that the large influence of the shielding prevents the molecules from photodissociation in the internal layer of the shell of TX Psc. The possibility of detecting C₂H₂ via the equivalent widths of the infrared lines in the circumstellar shell is discussed. Finally, we estimate the antenna temperature and the luminosity of the fine-structure lines of [CI]609µ and [CII]158µ of the envelope of TX Psc, respectively.     

Comparison of the Variations of CMEs and ICMEs with those of other Solar and Interplanetary Parameters During Solar Cycle 23

This paper examines the variations of coronal mass ejections (CMEs) and interplanetary CMEs (ICMEs) during solar cycle 23 and compares these with those of several other indices. During cycle 23, solar and interplanetary parameters had an increase from 1996 (sunspot minimum) to ∼2000, but the interval 1998–2002 had short-term fluctuations. Sunspot numbers had peaks in 1998, 1999, 2000 (largest), 2001 (second largest), and 2002. Other solar indices had matching peaks, but the peak in 2000 was larger than the peak in 2001 only for a few indices, and smaller or equal for other solar indices. The solar open magnetic flux had very different characteristics for different solar latitudes. The high solar latitudes (45^∘–90^∘) in both N and S hemispheres had flux evolutions anti-parallel to sunspot activity. Fluxes in low solar latitudes (0^∘–45^∘) evolved roughly parallel to sunspot activity, but the finer structures (peaks etc. during sunspot maximum years) did not match with sunspot peaks. Also, the low latitude fluxes had considerable N–S asymmetry. For CMEs and ICMEs, there were increases similar to sunspots during 1996–2000, and during 2000–2002, there was good matching of peaks. But the peaks in 2000 and 2001 for CMEs and ICMEs had similar sizes, in contrast to the 2000 peak being greater than the 2001 peak for sunspots. Whereas ICMEs started decreasing from 2001 onwards, CMEs continued to remain high in 2002, probably due to extra contribution from high-latitude prominences, which had no equivalent interplanetary ICMEs or shocks. Cosmic ray intensity had features matching with those of sunspots during 2000–2001, with the 2000 peak (on a reverse scale, actually a cosmic ray decrease or trough) larger than the 2001 peak. However, cosmic ray decreases started with a delay and ended with a delay with respect to sunspot activity.     

The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data

The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in 1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec. Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument. We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray observations, and dynamic radio spectra.