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The important role played by hard X-ray radiation as a diagnostic of impulsive phase energy transport mechanism is reviewed. It is argued that the sub-arc second resolution offered by an instrument such as the Pinhole/Occulter Facility (P/OF) can greatly increase our understanding of such mechanisms.
Contents include the detailed index for 1985; data for June 1985 (solar flares, solar radio bursts at fixed frequencies, solar X-ray radiation from GOES satellite graphs, mass ejections from the sun, and active prominences and filaments); data for January to May 1985 (solar flares January 1985, solar flares February 1985, solar flares March 1985, solar flares April 1985, solar flares May 1985, and number of flares August 1966 to June 1985); and the international geophysical calendar 1986.
Solar-Geophysical Data Number 498, February 1986, Part 2 (Comprehensive Reports), Data for August 1985, and Miscellenea contains the following: detailed index for 1985-86; data for August 1985--(Solar flares, Solar radio bursts at fixed frequencies, Solar X-ray radiation from GOES satellite, Mass ejections from the Sun, Active prominences and filaments); miscellaneous data--Meudon carte synoptique 13 May - 7 July 1985.
Solar-Geophysical Data Number 497, January 1986. Part 2: (Comprehensive Reports); Data for July 1985, and Miscellanea contains the following: a detailed index for 1985; data for July 1985-(solar flares, solar radio bursts at fixed frequencies, solar x-ray radiation from GOES satellite, mass ejections from the sun, active prominences and filaments); and miscellaneous data-(Meudon carte synoptique 16 April - 13 May 1985, number of solar flares August 1966 - July 1985).
The possibility is examined that in the course of its dynamical evolution, a single mass of interstellar gas would exhibit properties of diffuse clouds, dense clouds and finally also of clouds perturbed by shocks or intense UV or X-ray radiation generated by a star of its own creation. This concept provides a common thread through the bewildering diversity of physical and chemical compositional properties shown by interstellar clouds. From this perspective, instead of being static objects, interstellar clouds are possibly incessantly evolving from initially diffuse to later dense state and then to star formation which ultimately restructures or disperses the remaining cloud material to begin the whole evolutionary process once again. Based on a simplified study of interstellar chemistry from a dynamical perspective, the ideas are presented as an heuristic: to encourage thought on the future direction of molecular astrophysics and the need to consider the chemical behavior of interstellar clouds in conjunction with, rather than in isolation from, their dynamical behavior. A physical basis must be sought for the semiempirical temperature formula which has been given a critical role in the collapse of diffuse clouds. Self-shielding effects in the chemistry of CO were neglected and this drawback should be removed; the ability of the model to explain the fractional abundances of more complex molecules, such as cyanopolyynes, should be examined.
Solar-Geophysical Data Number 499, March 1986, Part 2 (Comprehensive Reports); Data for September 1985, and Miscellanea, contains the following: Detailed index for 1985 to 1986; Data for September 1985--(Solar flares, Solar radio bursts at fixed frequencies; Solar X-ray radiation from GOES satellite; Mass ejections from the Sun; Active prominences and filaments); (Meudon carte synoptique 7 July - 26 September 1985, Solar irradiance).
A model of the galactic X-ray source Cygnus X-3 (Cyg X-3) is presented which deviates from previous models by positing that the X-rays originate in a jet rather than a binary system consiting of an ordinary star and a collapsed object. In the new model, the 4.8 hour period of Cyg X-3 is caused by variable absorption which occurs as the jet precesses. The primary role of the accretion disk corona (ADC) in modulating Cyg X-3 radiation is to make the observed intensity of a blob of material in a jet appear dimmer by absorption. The needed derivation of the positional dependence of the density of the ADC is freed of some complications by assuming that only the inner regions of the disk are precessing, with a period shorter than 4.8 hours. This model permits the secondary star to be a supergiant, as indicated by the luminosity of the system. The model is especially helpful in interpreting production of radio outbursts and very high energy gamma rays.
Diffraction effects of X-ray optical systems are often (justifiably) ignored due to the small wavelength of the X-ray radiation. However, the extremely large obscuration ratio inherent to grazing incidence optical systems produces a profound degradation of the diffraction image over that produced by a moderately obscured aperture of the same diameter. The contradictory requirements of large collecting area and relatively short length of optical elements has tended to result in proposed designs containing many concentric shells with increasingly higher obscuration ratios. In this paper it is shown that diffraction effects in such systems can significantly affect the achievable optical performance at the low energy (long wavelength) end of the intended operating spectral range. Parametric diffraction-limited performance predictions for both imaging and spectrographic applications will be presented and compared to AXAF performance goals and/or BBXRT fabrication techniques.
The IUE observations were used to determine the composition of the ejecta (especially C and Si abundances) and to test models for the ionization and excitation of the ejecta of two oxygen-rich supernova remnants (N132D in the Large Magellanic Cloud and 1E 0102-7219 in the Small Magellanic Cloud). Time-dependent photoionization by the EUV and X-ray radiation from 1E 0102-7219 can qualitatively explain its UV and optical line emission, but the density and ionization structures are complex and prevent a unique model from being specified. Many model parameters are poorly constrained, including the time dependence and shape of the ionizing spectrum. Moreover, the models presented are not self-consistent in that the volumes and densities of the optically emitting gas imply optical depths of order unity in the EUV, but absorption of the ionizing radiation was ignored. It is possible that these shortcomings reflect a more fundamental limitation of the model assumptions. It is assumed that the electron velocity distribution is Maxwellian and that the energy deposited by photoionization heats the electrons directly. The 500 eV electrons produced by the Auger process may excite or ionize other ions before they slow down enough to share their energy with other electrons. Many of the excitations would produce photons that could ionize lower ionization stages.
According to results of Earth based observations and in situ measurements cometary nuclei are intensive sources of both the gaseous and the dusty matter. Investigations of the interaction between gas-dust cometary atmospheres and dust grains of the Zodiacal dust cloud reveals the presence of two principally possible mechanisms: meteor-like and explosive-type ones. The meteor-like mechanism is connected with bombardment of zodiacal dust particles by cometary molecules when the temperatures T = 2000 to 3000 K are developed. This mechanism can create over-saturated vapors of refractory elements (Fe, Si, C etc.) in cometary heads. The explosion-type mechanism is connected with high-velocity impacts between cometary and zodiacal dust particles resulting in the generation of high-temperature plasma (T = 10(exp 5) to 10(exp 7) K) and, hence, of x ray radiation and multicharged ions, i.e., with the processes not yet realized in the laboratory conditions.
The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.
The solar millisecond radio 'spikes' have been explained in terms of X-mode radiation generated by a maser near the electron gyrofrequency, acting on fast coronal electrons with a loss cone. This maser is a phenomenon described by quasi-linear theory. It is sensitive to the small first-relativistic correction to the gyrofrequency. Thus, it might be disrupted rather easily by nonlinear effects. The maximum radiation density that can be reached before the radiation entrains (phase-locks) the electrons and saturates the maser is discussed. If the observed durations of solar radio spikes are a measure of the rate of scattering into the loss-cone, then the inferred energy density is at least two orders of magnitude less than the energy density at which entrainment sets in. Also, maser emission from auroral kilometric radiation does not reach wave energies critical for electron entrainment. Maser emissions from flare stars, however, show 3-4 orders of magnitude higher radio fluxes and brightness temperatures than for the solar case and are likely to be saturated by entrainment.
The detailed predictions of a photoionization model previously outlined in Voit and Donahue (1990) to explain the optical line emission associated with cooling flows in X-ray emitting clusters of galaxies are presented. In this model, EUV/soft X-ray radiation from condensing gas photoionizes clouds that have already cooled. The energetics and specific consequences of such a model, as compared to other models put forth in the literature is discussed. Also discussed are the consequences of magnetic fields and cloud-cloud shielding. The results illustrate how varying the individual column densities of the ionized clouds can reproduce the range of line ratios observed and strongly suggest that the emission-line nebulae are self-irradiated condensing regions at the centers of cooling flows.
The Orbiter Stability Experiment (OSE) was developed to evaluate the steadiness of the STS Orbiter as a potential platform for instrumentation that would image the Sun in its extreme ultraviolet and soft X-ray radiations. We were interested in any high frequency motions of the Orbiter's orientation due to normal operations and manned activities. Preliminary results are presented of the observations. Other than the expected slow motion of the Orbiter within the specified angular deadband of 0.1 degrees during the observations, it was found that high frequency (above 1 Hz) angular motions (jitter) were not detectable at the 0.25 arc sec detection limit of the most sensitive detector, for most of the period of observation. No high frequency motions were recorded during intervals that were identified with vernier thruster firings. However, one short interval with detectable spectral power to a frequency of 10 Hz has been found to date. It has not yet been correlated with a particular activity going on at the time. The results of the observations may also be of value in assessing perturbations to the Orbiter's micro-gravity environment produced by normal operations.
By comparing the light curves in optical, hard X-ray, and soft X-ray wavelengths for eight well-observed flares, we confirm previous results indicating that the white light flare (WLF) is associated with the flare impulsive phase. The WLF emission peaks within seconds after the associated hard X-ray peak, and nearly two minutes before the 1-8 A soft X-ray peak. It is further shown that the peak power in nonthermal electrons above 50 keV is typically an order of magnitude larger, and the power in 1-8 A soft X-rays radiated over 2pi sr, at the time of the WLF peak, is an order of magnitude smaller than the peak WLF power.
An X-ray technique for the measurement of internal residual strain gradients near the continuous reinforcements of metal matrix composites has been investigated. The technique utilizes high intensity white X-ray radiation from a synchrotron radiation source to obtain energy spectra from small (0.001 cu mm) volumes deep within composite samples. The viability of the technique was tested using a model system with 800 micron Al203 fibers and a commercial purity titanium matrix. Good agreement was observed between the measured residual radial and hoop strain gradients and those estimated from a simple elastic concentric cylinders model. The technique was then used to assess the strains near (SCS-6) silicon carbide fibers in a Ti-14Al-21Nb matrix after consolidation processing. Reasonable agreement between measured and calculated strains was seen provided the probe volume was located 50 microns or more from the fiber/matrix interface.
We have used the High Resolution Imager (HRI) on ROSAT to image PSR 0656 + 14 at soft X-ray energies. With a net observing time of 10,326 s, we obtained a source event rate of 0.382 +/- 0.007 counts/s. Comparing the radial distribution of these counts between 15 and 100 arcsec to an empirically derived point spread function for HRI soft sources, we find no evidence of a spatially extended X-ray nebula to a limiting surface brightness of 1.67 x 10 exp -6 counts/s/sq arcsec, corresponding to a limit of 14 percent of the observed flux out to a radius of 100 arcsec. The X-ray emission of the pulsar is pulsed at the 0.385 s period of the radio pulsar, with a pulse fraction of 7 +/- 2.2 percent and a FWHM of 0.10 s. We discuss some models of the X-ray radiation of PSR 0656 + 14 compatible with both the HRI and PSPC results.
An important use of silicate glasses doped with terbium oxide (Tb2O3) is their use as fiber optic sensors for high-resolution imaging applications requiring the detection of x-rays (e.g. tomography and radiography). The x-ray radiation is absorbed by the glass, producing electron-hole pairs (excitons). The excitons migrate through the glass matrix and then recombine, emitting characteristic Tb(3+) luminescence in the optical wavelength region. This emission is due to forbidden transitions of 4f electrons and therefore has a long decay time. Long decay time is undesirable when imaging transient events since it results in blurring in time of the images. It has been reported elsewhere that in crystals Tb(3+) ions can act both as luminescence centers and as fluorescence traps. These traps can capture excitons and delay their recombination. This delayed fluorescence is seen as a long lived, secondary component to the luminescence decay curve, or afterglow. Such a secondary decay component to the luminescence decay of Tb(3+) has been observed before in soda glass following pulsed optical excitation. In order to determine the conditions under which afterglow occurs, an understanding of the material's luminescent properties is required.