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NASA NTRS1977

Studies of Transient X-Ray Sources with the Ariel 5 All-Sky Monitor

The All-Sky Monitor, an imaging X-ray detector launched aboard the Ariel 5 satellite, was used to obtain detailed light curves of three new sources. Additional data essential to the determination of the characteristic luminosities, rates of occurrence (and possible recurrence), and spatial distribution of these objects was also obtained. The observations are consistent with a roughly uniform galactic disk population consisting of at least two source sub-classes, with the second group (Type 2) at least an order of magnitude less luminous and correspondingly more frequent than the first (Type 1). While both subtypes are probably unrelated to the classical optical novae (or supernovae), they are most readily interpreted within the standard mass exchange X-ray binary model, with outbursts triggered by Roche-lobe overflow (Type 1) or enhancements in the stellar wind density of the companion (Type 2), respectively.

Kaluzienski, L. J.↗
NASA NTRS1976

Prolongation structures of nonlinear evolution equations. II

The prolongation structure of a closed ideal of exterior differential forms is further discussed, and its use illustrated by application to an ideal (in six dimensions) representing the cubically nonlinear Schroedinger equation. The prolongation structure in this case is explicitly given, and recurrence relations derived which support the conjecture that the structure is open - i.e., does not terminate as a set of structure relations of a finite-dimensional Lie group. We introduce the use of multiple pseudopotentials to generate multiple Baecklund transformation, and derive the double Baecklund transformation. This symmetric transformation concisely expresses the (usually conjectured) theorem of permutability, which must consequently apply to all solutions irrespective of asymptotic constraints.

Estabrook, F. B.↗
NASA NTRS1977

Acceleration of nucleons in interplanetary space and modulation of Jovian electrons at distances of 1 to 10 AU by corotating regions of solar origin

Corotating interaction regions (CIRs) are formed in interplanetary space when a fast solar-plasma flow overtakes a slow solar-wind stream. This paper shows that CIRs are closely related to two unusual phenomena observed during the flights of Pioneers 10 and 11. These include corotating periodic nucleon fluxes with energies of several MeV and variations in the intensity of relativistic Jovian electrons. Observational evidence is presented in favor of the idea that the nucleons are accelerated in CIRs located in interplanetary space at heliocentric distances of 1 to at least 10 AU, and a model is analyzed in which the acceleration takes place at the leading edge of a CIR. Pioneer data are cited which demonstrate that modulation by recurrent CIRs can explain the large-scale variations in Jovian electron intensity observed in interplanetary space.

Barnes, C. W.↗
NASA NTRS1977

Galactic distribution of X-ray burst sources

Data on X-ray bursts recorded by the OSO-8 and SAS-3 satellites and criteria (rise time, duration, recurrence) for X-ray bursts are examined in a study of possible correlation between the galactic longitude distribution of X-ray burst sources and globular clusters. Correlations are weak, with only two X-ray bursts sources (NGC6624 and the rapid burster) coinciding with globular clusters, another seven possibly coinciding, most not correlated. Ad hoc explanations (globular clusters obscured by dust clouds, bursts associated with remnants of disrupted globular clusters evolved into supermassive black holes) are considered briefly.

Lewin, W. H. G.↗
NASA NTRS1977

A comparison of solar wind streams and coronal structure near solar minimum

Solar wind data from the MIT detectors on the IMP 7 and 8 satellites and the SOLRAD 11B satellite for the solar-minimum period September-December, 1976, were compared with X-ray images of the solar corona taken by rocket-borne telescopes on September 16 and November 17, 1976. There was no compelling evidence that a coronal hole was the source of any high speed stream. Thus it is possible that either coronal holes were not the sources of all recurrent high-speed solar wind streams during the declining phase of the solar cycle, as might be inferred from the Skylab period, or there was a change in the appearance of some magnetic field regions near the time of solar minimum.

Nolte, J. T.↗
NASA NTRS1976

The physical properties of coronal holes

Coronal hole data obtained by Skylab during the period May 1973 to February 1974 are reviewed for the region from the photosphere out through the low corona. Coronal holes have a significantly lower density and temperature than the typical background corona, possess an open divergent magnetic field structure, and are the source of the high-speed solar wind stream which give rise to recurrent geomagnetic storms. The photospheric, chromospheric, and coronal signatures of coronal holes are described, and the evolution of coronal holes is examined, with attention to the lifetimes, the differential rotation, and the areas covered by the holes. The association of coronal holes to large-scale magnetic fields and to disk activity is considered.

Bohlin, J. D.↗
NASA NTRS1976

Solar particle emission

A variety of flare-associated and recurrent solar particle events are analyzed using the technique of 'mapping' the fluxes back to the estimated high coronal longitude of the interplanetary field line passing through the spacecraft. Often it is possible to separate temporal from spatial effects as well as those of coronal and interplanetary propagation. Considerable regularity appears in the coronal injection profiles deduced during events in 1969, 1972 and 1973, implying extended acceleration of protons about 0.3-7.5 MeV, helium and medium nuclei about 1 MeV/nuc and relativistic electrons. Clear associations are found in 1973 among energetic particle injection profiles, solar wind stream sources, and low coronal magnetic structure.

Roelof, E. C.↗
NASA NTRS1977

Office of university affairs management information system: Users guide and documentation

Data on the NASA-University relationship are reported that encompass research in over 600 schools through several thousand grants and contracts. This user-driven system is capable of producing a variety of cyclical and query-type reports describing the total NASA-University profile. The capabilities, designed as part of the system, require a minimum of user maintenance in order to ensure system efficiency and data validity to meet the recurrent Statutory and Executive Branch information requirements as well as ad hoc inquiries from NASA general management, Congress, other Federal agencies, private sector organizations, universities and individuals. The data base contains information on each university, the individual projects and the financial details, current and historic, on all contracts and grants. Complete details are given on the system from its unique design features to the actual steps required for daily operation.

Distin, J.↗
NASA NTRS1978

Critical issues in viscous flow computations

In developing computer programs to numerically solve the Navier-Stokes equations, the purpose of the computation must be clearly kept in mind. In the Air Force, the purpose is to provide design information on non-linear aerodynamic phenomenon for aircraft that perform throughout the flight corridor. This translates into the requirement for a computer program which can solve the time averaged compressible Navier-Stokes equations (with a turbulence model) in three dimensions for generalized geometries. The intended application of the results then controls the priorities in addressing critical issues. Recurrent problem areas encountered in the study of viscous flow include: (1) grid generation for arbitrary geometry; (2) numerical difficulties; (3) turbulence models; (4) accuracy and efficiency; and (5) smearing of discontinuities.

Hankey, W. L., Jr.↗
NASA NTRS1978

Long-term studies with the Ariel-5 asm. 1: Her X-1, Vela X-1 and Cen X-3

Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1 and Cen X-3 accumulated with the Ariel-5 all-sky monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the approximately 35-d variation of Her X-1, for which we can refine the period to 34.875 plus or minus .030-d. No such longer-term periodicity less than 200-d is observed from Vela X-1. The 26.6-d low-state recurrence period for Cen X-3 previously suggested is not observed, but a 43.0-d candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

Holt, S. S.↗
NASA NTRS1978

NASA aviation safety reporting system

An analytical study of reports relating to cockpit altitude alert systems was performed. A recent change in the Federal Air Regulation permits the system to be modified so that the alerting signal approaching altitude has only a visual component; the auditory signal would continue to be heard if a deviation from an assigned altitude occurred. Failure to observe altitude alert signals and failure to reset the system were the commonest cause of altitude deviations related to this system. Cockpit crew distraction was the most frequent reason for these failures. It was noted by numerous reporters that the presence of altitude alert system made them less aware of altitude; this lack of altitude awareness is discussed. Failures of crew coordination were also noted. It is suggested that although modification of the altitude alert system may be highly desirable in short-haul aircraft, it may not be desirable for long-haul aircraft in which cockpit workloads are much lower for long periods of time. In these cockpits, the aural alert approaching altitudes is perceived as useful and helpful. If the systems are to be modified, it appears that additional emphasis on altitude awareness during recurrent training will be necessary; it is also possible that flight crew operating procedures during climb and descent may need examination with respect to monitoring responsibilities. A selection of alert bulletins and responses to them is presented.

Source record↗
NASA NTRS1977

Long-term behavior of MXB 1730-335

The rapid burster MXB 1730-335 was detected on at least two occasions in 1971 and 1972 by Uhuru, and coverage is available from late 1970 to early 1973. Combined with ANS coverage in 1975 and 1976, as well as published SAS-3 and Ariel-5 observations (1976-1977), a unique record of long-term burst activity is now available for this source. There appear to be burst-active states of approximately one to two months' duration that occur with a duty cycle of about 15%. The burst activity appears to be recurrent with a time scale of roughly 0.5 to 1 year. Implications for burster models are discussed.

Grindlay, J. E.↗
NASA NTRS1978

Positions of galactic X-ray sources - l/II/ between 320 and 340 deg

The precise (20-40 sec) positions of seven X-ray sources in the celestial region corresponding to the galactic longitude range from 320 to 340 deg are reported. The sources include a recurrent transient X-ray source (MX1608-52) and a source 2S1553-542 coincident with a gamma-ray source within the given errors of position. The positions reported reduce the previously reported areas of the error region for six of the sources by factors ranging from 10 to 100. The presented results add confidence to the proposed radio candidates for 4U1624-49 and 4U1642-45 considered by Sanduleak and Dolan (1974) and Seaquist (1977).

Apparao, K. M. V.↗
NASA NTRS1977

Temporal evolution of the equatorial K-corona

Variation of the equatorial K-corona radiance at 2.5 solar radii from the sun center was studied on a daily basis during the Skylab mission (May 1973 to February 1974). The radiance data may be divided into three periods, the first characterized by a smooth variation in time, the second by a signal that is neither persistent in the short term nor recurrent from one limb passage to the next, and the third (and longest period) by a signal exhibiting an orderly, periodically increasing intensity. The data may be interpreted as indicating a general simplification of the coronal magnetic field; harmonic analysis of the surface field provides additional information on the evolution of the equatorial K-corona structures.

Macqueen, R. M.↗
NASA NTRS1978

The behavior of a convergent plate boundary - Crustal deformation in the South Kanto district, Japan

The northwesternmost part of the Sagami trough, a part of the Philippine Sea-Eurasian plate boundary, was ruptured during the great South Kanto earthquake in 1923. Very extensive and frequent geodetic measurements of crustal deformation have been made in the South Kanto district since the 1890's, and these constitute the most complete data set on crustal movements in the world. These data were reanalyzed and interpreted and according to our interpretation indicate the following sequence of events. The coseismic movements were due to oblique thrust and right lateral slip of about 8 m on a fault outcropping at the base of the Sagami trough. This was followed by postseismic deformation resulting from reversed afterslip of 20-60 cm that occurred at an exponentially decaying rate in time. The interseismic deformation is produced by steady subduction at a rate of about 1.8 cm/yr. During subduction the top 10-15 km of the plate boundary is apparently locked, while deeper parts slip aseismically at an irregular rate. No significant precursory deformation was observed. The recurrence time for 1923 type earthquakes is 200-300 years. The Boso and Miura peninsulas are broken into a series of fault-bound blocks that move semi-independently of the surrounding region. The subduction zone itself, where it is exposed on land, is shown to be a wide zone encompassing several faults that are active at different times.

Scholz, C. H.↗
NASA NTRS1978

Optical identification of 4U 1608-52

Analysis of astronomical plates obtained with a CTIO 4m telescope has revealed the probable optical counterpart of the recurrent flaring (or transient) X-ray source 4U 1608-52. Since the object is most probably a galactic source, it is not a typical galactic nova. An error box evaluation of the hypothesis is presented, and compared to other large burster error boxes, notably Aql X-1. Limits on the reddening and extinction of the object are set, permitting an estimation (89 kpc) of the object's distance.

Grindlay, J. E.↗
NASA NTRS1978

Thermal limit for spherical accretion and X-ray bursts

A mechanism is described whereby the rate of spherical accretion on a collapsed object and the resulting X-ray luminosity can be limited by thermal heating and evaporation of the accreting gas. The luminosity limit can be a factor of the order of 100 below the corresponding Eddington limit. Steady accretion flow is not possible within a range above this limit, and X-ray bursts can be produced by accretion surges resulting from the cooling and collapse of a heated gas shell above a critical optical depth. The luminosity and approximate recurrence rate of the bursts from NGC 6624 and other burst sources may then be understood. A general model for bursters is proposed in which massive (about 10 to 100 solar masses) black holes, from massive stars and the cores of disrupted globular clusters, undergo supercritical spherical accretion in interstellar clouds. Both X-ray and gamma-ray bursts are predicted to have similar hard X-ray (about 200 keV) spectra, though high average accretion rates and central optical depths also yield a comparable luminosity at around 5 keV from a Comptonized blackbody spectrum in the X-ray bursts and associated steady sources.

Grindlay, J. E.↗
NASA NTRS1978

Interplanetary gas. XXII - Interaction of comet Kohoutek's ion tail with the compression region of a solar-wind corotating stream

An apparently successful identification of a comet-tail feature with a solar-wind event is presented. Photographs of comet Kohoutek 1973f show a large-scale disturbance in the middle and outer regions of the ion tail early on January 20 of 1974. On the previous and succeeding days the comet had, however, a 'normal' and less active appearance. The peculiar tail structure is linked to an encounter with rapidly changing solar-wind conditions on the forward edge of the high-velocity solar-wind stream which encountered the earth late on January 24. The stream produced a geomagnetic storm of the recurrent type. The high-speed stream appears to have been associated with a large near-equatorial coronal hole which underwent central meridian passage on January 22. It is proposed that the comet was in the compression region on the stream forward edge at the time of formation of the tail disturbance. The accuracy of the time delays is actually tested by an application of the wind shock theory of ionic tail orientations.

Niedner, M. B., Jr.↗