Modeling the Local Interstellar Medium

The state of our observational and theoretical knowledge of the localinterstellar medium (LISM) is reviewed. The LISM stretches out from thelocal Cloud, surrounding the solar system to the boundary of the LocalBubble, which is a region of distinct anticorrelation between HI (N _H< 10²⁰ cm^-2) and 1/4 keV diffuse soft X-rays. After discussingsome key observations in soft X-rays, obtained by ROSAT and DXS, and inthe EUV by the EUVE satellite and the EURD instrument onboard Minisat, Iwill critically review models of the LISM. Since we cannot determine theplasma state (temperature, density, etc.) directly, the best plasmadiagnostic tool is high resolution spectroscopy. The interpretationof the data then has to rely heavily on plasma emission models. I willpoint out several caveats in the standard procedure. Preference is givento dynamical models of the Local Bubble in general and to non-equilibriumplasma emission models in particular, which have to be calculatedself-consistently. Such a model can explain (i) the deficiency of EUVlines as observed by EUVE, (ii) the dispersion measure and scintillationproperties of a nearby pulsar, (iii) the existence of local neutral HIclouds, and (iv) OVI absorption line widths. New model spectra of theLISM will be presented and briefly compared with DXS, EUVE and preliminaryEURD results.     

Using scintillation measurements to achieve high spatial resolution in photometric solar observations

The RISE/PSPT (Radiative Inputs from the Sun to the Earth/Precision Solar Photometric Telescopes) experiment will attain high differential photometric precision in full-disk solar images with 1 arc sec pixels. To achieve this spatial resolution it will be necessary to use frame selection techniques to minimize the effects of atmospheric seeing. We report here on experiments to use a simple scintillation monitor as a trigger or veto for imaging observations.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.     

The solar O i λ 7773 triplet

The reduction of observations of the O i 7773 triplet obtained at high spatial resolution (0.5) at two disk positions is described. Two sets of triplet profile data are presented at each disk position. One set represents data taken from 0.5 regions centered on the brightest granules, while the other set represents data taken from 0.5 regions centered on the cooler infalling intergranular material.     

The Science Operations Centre of MINISAT-01

The Scientific Operations Centre (C.O.C.) takes care of all aspects of theMinisat-01 Mission related to the payload and its scientific instruments. Operations planning, preparation of commands, monitoring of the scientific instruments and data processing and distribution are the daily tasks carried out at the COC. We review these tasks along the operational life of Minisat-01 and we present a summary of the science operations andsome statistics on the usage of the satellite.     

The blanketing in the rocket ultraviolet from 225.2 to 319.6 nm

The blanketing effect for the solar disc center and its value near the limb (cos = 0.23) are obtained for the rocket ultraviolet region using the Harvard center and limb spectra. The value of for the disc center appears to be 0.67 (on average) relative to the quasicontinuum. The essential decrease of towards the limb is also revealed.     

Orbite de l'etoile double visuelle ADS 1538 = Σ 186

The physical and orbital elements of the binary star ADS 1538 = Σ 168 (α₁₉₀₀ = 01^h50^m.7, δ₁₉₀₀ = +01°21'; α₂₀₀₀ = 01^h55^m·8, δ₂₀₀₀ = +01°51') are determined. The absolute visual magnitudes of the two components are 4^m.04 resp. 4^m.17, the masses 1.34 M_⊙ resp. 1.29 M_⊙.     

Magnetic field measurements on four yellow supergiants. I

Multiyear high precision measurements of the longitudinal component of the magnetic field (B_e) of four supergiants are reported: Aqr (G0 Ib), Aqr (G2 Ib), Gem (G8 Ib), and Peg (K2 Ib). The best measurement accuracy, =0.8 G, was achieved for Peg. A Monte Carlo method was used to test the reliability of the derived measurement errors. The differences between the observational errors and the calculated Monte Carlo errors were 3.2%. For Aqr and Aqr no statistically significant value of the magnetic field was recorded when averaged over a night. For eGem the following overnight average values of the magnetic field were recorded on five nights: 11.1±2.7 G, 9.8±2.5 G, –10.5±3.0 G, 38.1±7.4 G, and 5.3±1.5 G. For Peg the magnetic field recorded over two nights was –5.3±0.9 G and – 2.7±0.8 G.Translated from Astrofizika, Vol. 48, No. 1, pp. 15–28 (February 2005).     

Three gamma-ray sources with large angular sizes

From an analysis of the data from the gamma-ray satellite COS-B and from radio measurements of CO molecules, it appears probable that the three gamma-ray sources 2CG 036+01, 218-00, 235-01 are either isolated giant molecular clouds or superpositions of clouds unresolved by the detector.     

The influence of spectral resolution on line blending and wavelength positions in the solar UV spectrum

For representative sections of the solar UV spectrum ( 2765 Å– 2790 Å, 2765 Å– 2805 Å) the line density and the accuracy of wavelength positions of absorption features are derived as function of the spectral resolution. In low resolution spectrograms unresolved blends may shift intrinsic wavelength positions of absorption lines by amounts up to a few tenths of the spectral resolution.The results obtained for the solar spectrum are applied to the flux spectrogram of CMi.Guest Investigator in the BUSS Program jointly performed by the Space Research Laboratory, Utrecht, The Netherlands, and the NASA L. B. Johnson Space Center, Houston, U.S.A.     

Variation of the profiles of medium-strong photospheric lines with heliographic latitude

The asymmetric profiles of 11 metallic lines are studied, at = 0.3, as functions of . Their variations cannot be interpreted as due to temperature effects, but might imply a dependence on of the photospheric velocity field.This work has been supported by the CNR through the Gruppo Nazionale di Astronomia.     

Long-range coherence of the radar field scattered by a rotating mercury

We consider the spatial-temporal properties of the speckle patterns formed when coherent radio waves are scattered by planets. At a speckle diameter of only a few kilometers, the speckle patterns are shown to be displaced in frozen form by distances larger than the Earths diameter due to the spin-orbital motion; i.e., long-range coherence of the radar field takes place. We estimate the coherence losses of the echo signals from Mercury due to the decorrelation of the patterns, which do not exceed or comparable to 10^-4 in order of magnitude for ground-based interferometers. Such small losses imply a high degree of frozenness of the speckle pattern everywhere within the Earth, i.e., on a global scale. This allows us to formulate and solve the unprecedented problems of precision measurements of the instantaneous spin vector components for terrestrial planets by using radars distributed all over the globe.Translated from Astronomicheskii Vestnik, Vol. 38, No. 6, 2004, pp. 513–518.Original Russian Text Copyright © 2004 by Kholin.     

Spatial correlation of Hα filaments and photospheric velocity

The location of H filaments is compared with maps of the photospheric line of sight velocity V and the magnetic field H . It is found that (1) H filaments are associated with regions of ¦V ¦ 300m s^–1, (2) always both positive as well as negative velocities are present under H structures, (3) stable (long lasting) portion of filaments frequently occur at the position of H = 0 as well as V = 0 lines, (4) this association remains valid for the longitudes less than 50° from central meridian.     

Current sheet model of a normal prominence in which the background magnetic lines show a ‘dip structure’

We propose a simple 2D current sheet model of a normal prominence, in which the lines of the background magnetic field have the dip structure which seems to be required for such an object to form and to be stably supported.     

Hα profiles from electron-heated solar flares

We briefly review the status of models of optical flare heating by electron bombardment. We recompute Brown's (1973a) flare model atmospheres using considerably revised radiative loss rates, based on Canfield's (1974b) method applied to , L, and H^–. Profiles of are computed and compared with observation. The computed profiles agree satisfactorily with those observed during the large 1972 August 7 flare, if spatial and velocity inhomogeneities are assumed. The electron injection rate inferred from is one order of magnitude less than that inferred from hard X-rays, for this event. This may be due to either (1) the neglect of a mechanism that reduces the thick-target electron injection rate or (2) failure to incorporate important radiative loss terms.     

Development of MINISAT 01 Scientific Payload

The MINISAT design is a modular concept, and accordingly the ScientificPayload of Mission 01 is a self-contained Payload Module (PLM). Thisphilosophy offers the advantage that the Payload and the Platform may beassembled independently and coupled together at a later stage. Themechanical, thermal, power and data interfaces have to be secured alongthe design and development phases. The MINISAT 01 PLM with threeinstruments, EURD, LEGRI and CPLM, integrates on a structural tray adozen of equipment supplied by more than ten participant Institutions. TheAssembly, Integration and Verifications (AIV) of the PLM, was performedat INTA, providing the common structural, harnessing and thermal controlsubsystems. In this paper an overview is presented of the PLM layout of thedifferent models and the qualification and acceptance testing.     

Impulsive EUV bursts observed in Civ with OSO-8

Time sequences of profiles of the 1548 line of C iv containing 51 EUV bursts observed in or near active regions are analyzed to determine the brightness, Doppler shift and line broadening characteristics of the bursts. The bursts have mean lifetimes of approximately 150s, and mean increases in brightness at burst maximum of four-fold as observed with a field of view of 2 × 20. Mean burst diameters are estimated to be 3, or smaller. All but three of the bursts show Doppler shifts with velocities sometimes exceeding 75 km s^–1; 31 are dominated by red shifts and 17 are dominated by blue shifts. Approximately half of the latter group have red-shifted precursors. We interpret the bursts as prominence material, such as surges and coronal rain, moving through the field of view of the spectrometer.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

关于RSC(IERS)88 C01实现中的几个问题的讨论

本文讨论了IERS的RSC 88C01实现过程中在有关基本源选取和参考架定向确定等方面存在的问题,分析了它们对IERS天球参考架的影响,提出了建立和维持高精度天球参考架的几点建议。     

Theory of solar radio pulsation

We show that the observed modulation of some coronal microwave, X-ray and Type III emission into pulses of 10 sec intervals is a consequence of the stimulation of electron cyclotron waves propagated in the whistler mode in dipole-like bipolar regions of dimension 0.2 R . Assuming that a power law spectrum of 10 keV electrons with a slope similar to solar flare protons can be trapped in a bipolar region, we show that whistlers can be generated by pitch angle instability. The resultant 10 sec bounce motion of whistler wave trains leads to enhanced, modulated emission in microwave and X-ray frequencies by pitch angle scattering of MeV electrons, and to modulated Type III emission by scattering with coherent plasma waves. A direct prediction of the theory is the existence of sympathetic pulsations at two sources a fraction of a solar radius apart. A second test of the theory is that modulated Type III emission should show strong polarization.This work was conducted under U.S. Air Force Space and Missile Systems Organization (SAMSO) Contract No. F04701-69-C-0066.     

An empirical approach to cosmology

A two-component model of the universe is proposed, based on the observations of discrete extragalactic sources and the microwave background radiation. The large scale dynamics of the universe is determined by the radiation component and it leads to a characteristic size of the universe 6×10⁵ Mpc and an age 10¹² yr. The second component, that of matter, occurs in discrete sources which group together in super-superclusters of characteristic size 6×10³ Mpc and age 10¹⁰ yr. It is suggested that our Galaxy belongs to one of these super-superclusters and that observations of discrete sources are confined to this unit. A reasonable agreement with the cosmological tests is obtained on the assumption that the geometry within a typical super-supercluster is Euclidean and that the redshifts of galaxies arise from Doppler effect due to motions originating in a local explosion which gave birth to the super-supercluster. Further observational checks on this model are proposed.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation     

Identification of the donor in GRS 1915+105

This paper describes the results of the MINISAT-01mission after two year in orbit since the launch on April 21^st of1997. It also describes the MINISAT-01 behavior during these years anddescribes, the evolution of the Satellite, by subsystems. Graphics of themost important parameters will be shown to display the difference betweenthe beginning of life and two years after.The paper details the most important events during the Satellite's life suchas the battery overcharge, temperature evolution, onboard computer reset,software updating, and communication failures.