Evaluation of gas production rates in some comets

Emission fluxes of CN, C₂ and C₃ carbon-bearing molecular species observed in the coma of comets Bennett (1969i 1970II), West (1975n 1976VI), P Halley (1982i), Hartley-Good (19851) and Bradfield (1987s) are analysed in the framework of Haser model. CN, C₂ and C₃ production rates are determined using recently derived fluorescence efficiencies. The dependence of CN, C₂ and C₃ production rates on the heliocentric distance and the possible correlations among these radicals is studied and briefly discussed.     

The impulsive phase of a large solar limb flare of June 20, 1989

On 1989 June 20, we observed in H the impulsive phase of a 3B/X1.6 limb flare with high temporal resolution. Line profiles have been acquired every 2.3 s with an imaging spectrograph. During the eruption of a filament we observed in H a moving plasma blob from what we believe to be a second loop which correlated spatially and temporally with a microwave source at 1.4 GHz observed by VLA. A magnetodynamic model is used to understand the development of the moving plasma blob.     

An analysis of 1983 observations of facular contrast with an extreme limb photometer

Analysis of facular contrast I/I _qs from Extreme Limb Photometer (ELP) data of the summer of 1983 yield a mean contrast of 0.91 ± 0.19% and 1.57 ± 0.16% for apertures 1 and 2 located at = 0.198 and at = 0.111, respectively. The ratio of the mean contrast in the outer aperture (closer to the limb) to that of the inner one is 1.71 ± 0.40, indicating an increase in the mean facular contrast toward the limb. This result is in agreement with observations made in 1975, 1979, and 1982. The errors are dominated by the random presence of solar active regions. The combined results from all seasons follow an approximately ^–1 curve. Facular excess solar oblateness signals for 1983 are 33.8 ± 6.6 arc ms and 16.5 ± 2.1 arc ms for ELP apertures 1 and 2, respectively, in reasonable agreement with the 1983 excess solar oblateness results of Dicke, Kuhn, and Libbrecht (1985).     

Propagation of solar cosmic rays: Diffusion versus focused diffusion

This paper is designed to bring to the attention the fact that the effect of focusing of solar energetic particles is always essential as compared with scattering, no matter how small the value of the mean free path may be. That is why, an ordinary (focusing-free) diffusion approach can not be applied to the solar cosmic ray transport. In the case of high-energy solar particles, the focused diffusion is demonstrated to lead to a power law decay of energetic particle intensity much like an ordinary diffusion. However, the power law index of the decay is renormalized by the focusing.     

On solving Kepler's equation for nearly parabolic orbits

We deal here with the efficient starting points for Kepler's equation in the special case of nearly parabolic orbits. Our approach provides with very simple formulas that allow calculating these points on a scientific vest-pocket calculator. Moreover, srtarting with these points in the Newton's method we can calculate a root of Kepler's equation with an accuracy greater than 0.001 in 0–2 iterations. This accuracy holds for the true anomaly || 135° and |e – 1| 0.01. We explain the reason for this effect also.Dedicated to the memory of Professor G.N. Duboshin (1903–1986).     

A filament eruption and accompanying coronal field changes on November 5, 1992

An H filament eruption on November 5, 1992 was fully observed in H with the Hida Flare Monitoring Telescope, while Yohkoh's Soft X-ray Telescope observed the pre- and post-eruption evolution of the coronal magnetic fields. From the H data, including the red and blue wings, we have reconstructed the rise of the filament, including trajectory, velocity, and acceleration. In combination with the Yohkoh data this reconstruction suggests that the filament had several interactions with other coronal magnetic fields during the eruption. The Yohkoh data also shows pre-eruption changes in the coronal fields and several post-eruption bright coronal structures. The pre-eruption changes are interpreted as a partial opening of the corona, indicating that it is not necessary to have a complete opening of the corona in order for a filament to erupt and we discuss the several possible contributions from emerging flux. The post-event bright coronal structures are compared with theory and with a cleaner filament eruption event on July 31, 1992. These comparisons suggest that, although there are many similarities, it is hard to completely reconcile the observations with the existing theory.     

Singular points of the polarization tensor

The problem to compute the magnetic field above the chromosphere using data of the vector = B _t/Bt that gives the projected field direction can be solved with different approximations. The field of direction vectors is, however, not the only field accessible to observations. The Stokes parameters, which are components of the radiation tensor, can be measured at each point of the image plane. The directions of the eigenvectors of the radiation tensor define two mutually orthogonal systems of integral curves in the image plane. These families of curves have singular points, which are generally of different type than those of the vector field. When the morphology of H chromospheric fibrils are used to infer the topology of the magnetic field, a similar problem is met, suggesting that singular points should also be present there.     

Connection between X-ray and optical variability in NGC 4151

We have used long light curves in the X-ray (ARIEL V, EXOSAT, Ginga and others), UV (IUE), and optical (data of intensive ground-based monitoring) ranges of NGC 4151 to investigate connections between variations in these spectral fields. Applying Fourier (CLEAN algorithm) and modern cross-correlation analysis, we revealed the different character of the variability and the cross-correlation between high and low states of the nucleus. In contrast to earlier results, we found that X-ray and optical fluxes correlate in the active state without any apparent delay.In the power spectrum of the optical and X-ray light curves in the high state we found the existence of the same period of about 65 days, which disappeared in the low state.We confirmed previous data that X-ray variations correlate more strongly with UV and optical continuum variability during the low state, but it is possible that the optical variations appear to lag behind those involving X-rays by several tens of days.Strong variations in H line profile and [Fe X]6374 line intensity variations correlate with the observed X-ray covering dip in 1990 (Yaqoobet al., 1993).We discuss briefly the implications of these results.