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Moore, R. L.

Publications and source records attributed to Moore, R. L..

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Structure of the sunspot penumbra

An exceptionally highly resolved sunspot photograph is presented which reveals the fine-scale structure of the photospheric penumbra down to 0.2 arcsec. The photograph was taken through a glass filter in a 170-A FWHM band centered on 4660 A on the 65-cm vacuum Gregorian telescope at Big Bear Solar Observatory during practically perfect seeing. The photograph reveals the penumbra to be full of extremely fine-scale fibril structures, with apparent widths near the resolution limit. The three-dimensional structure of the photospheric penumbra is seen to be similar to that of the chromospheric penumbra and superpenumbra, with dark fibrils arching above a lower brighter structure and many of the bright fibrils representing portions of wider bright structures shining through the narrow spaces between the elevated dark fibrils. Thus, in contrast to previous pictures, much of the dark component of the photospheric penumbra is not physically analogous to the intergranular dark lanes in the normal photosphere.

Moore, R. L.↗
NASA NTRS1981

X-ray and H-alpha observations of a filament-disappearance flare - An empirical analysis of the magnetic field configuration

On August, 29, 1973, a flare event occurred that involved the disappearance of a filament near central meridian. The event, well-observed in X-rays on Skylab and in H-alpha, was a four-ribbon flare involving both new and old magnetic inversion lines which were roughly parallel. The H-alpha, X-ray, and magnetic field data are used to deduce the magnetic polarities of the H-alpha brightening at the footpoints of the brightest X-ray loops. It is suggested that the event involved a reconnection of magnetic field lines rather than a brightening in place of preexisting loops. The simultaneity of the H-alpha brightening onsets in the four ribbons and the apparent lack of an eruption of the filament are consistent with this interpretation.

Kahler, S. W.↗
NASA NTRS1981

Dynamic phenomena in the visible layers of sunspots

The empirical properties of the various dynamic phenomena are reviewed and interrelated, with emphasis placed on recent observational results. On the basis of the observations, it is proposed that umbral dots and penumbral grains are essentially the same phenomenon and that the observational goal of highest priority with respect to both the origin of the periodic phenomena and the problem of the missing heat flux is to better determine the nature of these elementary bright features. The dynamic phenomena discussed are features or events that display spectral evidence for mass motion or that change appreciably in brightness or position on time scales less than approximately one hour. It is also concluded that nonoscillatory convection in umbral dots may well contribute strongly to umbral turbulence as presently observed.

Moore, R. L.↗
NASA NTRS1981

Dynamic phenomena in sunspots

A detailed summary of observed dynamic phenomena associated with sunspots is presented, together with a description of the observational techniques and available analytical formulations for the processes under study. The phenomena detected thus far are grouped into aperiodic events and oscillations and waves. Aperiodic phenomena comprise umbral flares, the superpenumbra, and inverse Evershed flow. Internal, aperiodic manifestations include penumbral grains, the photospheric penumbral dark fibrils, Evershed flow, umbral dots, the inhomogeneity of the umbral magnetic field, and umbral turbulence. Oscillations and flashes are seen in the umbra, while running waves and dark puffs have been detected in the penumbra, and oscillations are located in the photosphere. All the observed features are evidence of mass motion and change on time scales of less than an hour.

Moore, R. L.↗
NASA NTRS1980

Coronal holes, the height of the chromosphere, and the origin of spicules

Analysis of 650 microphotometric scans across the solar limb reveals that the H(alpha) chromosphere is slightly taller inside coronal holes than in quiet regions outside holes. The change in height occurs as a step at the hole boundaries; this suggests that the increase with latitude in the average height of spicules found by Lippincott and by Athay was the average result of upward steps at the polar hole boundaries rather than a gradual latitude trend. It is estimated that the power consumed by spicules is of the same order as that returning by conduction from the corona, but the bulk of the spicules (which sets the height of the chromosphere) shows almost no response. It is concluded that spicules are not caused by heat conduction from the corona but are driven from below, suggesting that spicules are more closely connected with the heating of the corona than with its cooling.

Rabin, D.↗
NASA NTRS1980

A continuum bright point at the penumbral edge

A small continuum bright point, observed at the outer edge of the penumbra of a small spot in a large complex spot group, is related to an occurrence beneath the suns's surface. The characteristics of the point appear to be unique, and the name 'penumbra-periphery bright point' is proposed.

Zirin, H.↗
NASA NTRS1980

Optical and infrared variability of B2 1308+326

Optical and infrared polarimetric and photometric observations of the BL Lacertae object B2 1308+326 during its high-luminosity outburst in the spring of 1978 are reported. The energy distribution, polarization at 0.6 and 2.2 microns, flux and polarization variability and position angle and strength of polarization variations of B2 1308+326, which has a luminosity greater than 10 to the 48th ergs/sec, are observed to be similar to those of BL Lac objects of much lower luminosity, suggesting the same emission process. Models of BL Lac object emission accounting for the high luminosity of B2 1308+326 are examined, and the isotropic synchrotron model is found to be more applicable to the optical and infrared emission of BL Lac objects than a model invoking relativistically enhanced emission.

Moore, R. L.↗
NASA NTRS1980

The filament eruption in the 3B flare of July 29, 1973 - Onset and magnetic field configuration

The filament eruption in the large expanding two-ribbon solar flare which occurred July 29, 1973 is discussed. Observational evidence is presented for the preflare magnetic field configuration, the nature of the filament destabilization and triggering of the flare, and the magnetic field configuration after the filament eruption. The observations show that the filament is under an arcade of closed magnetic field lines prior to the eruption. The eruption of the filament and the onset of the two-ribbon H-alpha flare are preceded by precursor activity in the form of small H-alpha brightenings and mass motion along the neutral line and well below the bottom edge of the filament. The precursor H-alpha brightenings and the first brightenings in the flare ribbons are in the vicinity of the steepest magnetic field gradient in the flare region.

Moore, R. L.↗
NASA NTRS1979

Empirical studies of solar flares: Comparison of X-ray and H alpha filtergrams and analysis of the energy balance of the X-ray plasma

The physics of solar flares was investigated through a combined analysis of X-ray filtergrams of the high temperature coronal component of flares and H alpha filtergrams of the low temperature chromospheric component. The data were used to study the magnetic field configuration and its changes in solar flares, and to examine the chromospheric location and structure of X-ray bright points (XPB) and XPB flares. Each topic and the germane data are discussed. The energy balance of the thermal X-ray plasma in flares, while not studied, is addressed.

Moore, R. L.↗
NASA NTRS1979

Composite properties for S-2 glass in a room-temperature-curable epoxy matrix

The authors have measured thermal and mechanical properties of several composites of S-2 glass fiber in a room-temperature-curable epoxy matrix. The filament-wound composites ranged from 50 to 70 vol% fiber. The composites had generally good to excellent mechanical properties, particularly in view of the moderate cost of the material. However, the composites showed rapid increases in transverse thermal expansion above 50 C, and this property must be carefully considered if any use above that temperature is contemplated.

Clements, L. L.↗
NASA NTRS1977

H-alpha macrospicules - Identification with EUV macrospicules and with flares in X-ray bright points

The paper presents observational evidence that two newly observed transient solar phenomena, EUV macrospicules and X-ray bright-point flares, are closely related. Time-lapse H-alpha filtergram observations of the limb in quiet regions show small surgelike eruptions called H-alpha macrospicules. From the similarity of H-alpha macrospicules and EUV macrospicules, and from comparison of simultaneous H-alpha and He II 304 A observations, we conclude that H-alpha macrospicules are EUV macrospicules viewed in H-alpha, although most EUV macrospicules are too faint in H-alpha to appear on H-alpha filtergrams of normal exposure. From comparison of simultaneous X-ray and H-alpha observations of flares in X-ray bright points situated on the limb, we show that flares in X-ray bright points often produce H-alpha macrospicules.

Moore, R. L.↗
NASA NTRS1975

Heating and cooling of the thermal X-ray plasma in solar flares

Characteristic times for the heating and cooling of thermal plasma in X-ray flares are estimated from the time profile of the flare and from the temperature, emission measure and length scale of the flare-heated plasma. It is implied from the empirical values for the characteristic times that flares are produced by magnetic field reconnection; that conductive cooling of the plasma dominates radiative cooling; and that reconnection heating and conductive cooling are approximately in balance at thermal X-ray maximum.

Moore, R. L.↗
NASA NTRS1975

Umbral oscillations and penumbral waves in H alpha

Examples are presented of umbral oscillations observed on Big Bear H-alpha filtergram movies, and the relation between umbral oscillations and running penumbral waves occurring in the same sunspot is investigated. Umbral oscillations near the center of the umbra are probably physically independent of the penumbral waves because the period of these umbral oscillations (150 sec) is shorter than the penumbral wave period (270 sec), but not a harmonic. Dark puffs emerge from the edge of the umbra and move outward across the penumbra, and have the same period as the running penumbral waves. These dark puffs are interpreted to be the extension of chromospheric umbral oscillations at the edge of the umbra. It is suggested that the dark puffs and the running penumbral waves have a common source: photospheric oscillations just inside the umbra.

Moore, R. L.↗
NASA NTRS1975

Analysis of OGO-5 and OSO-7 X-ray data

The physical nature of solar flares implied by the data was studied. The empirical results were obtained primarily from the OGO-5 and OSO-7 X-ray data in combination with optical data. The principal conclusions regarding the physics of flares are the following. (1) Flares are produced by magnetic field reconnection. (2) The resulting thermal X-ray plasma is cooled primarily by heat conduction rather than by radiative cooling. (3) The heating and cooling of the thermal X-ray plasma are approximately in balance during the maximum phase of the flare.

Moore, R. L.↗
NASA NTRS1973

On the generation of umbral flashes and running penumbral waves.

From a review of the observed properties of umbral flashes and running penumbral waves it is proposed that the source of these periodic phenomena is the oscillatory convection which Danielson and Savage (1968) and Savage (1969) have shown is likely to occur in the superadiabatic subphotospheric layers of sunspot umbras. Periods and growth rates are computed for oscillatory modes arising in a simple two-layer model umbra. The results suggest that umbral flashes result from disturbances produced by oscillatory convection occurring in the upper subphotospheric layer of the umbra, where the superadiabatic temperature gradient is much enhanced over that in lower layers, while running penumbral waves are due to oscillations in a layer just below this upper layer.

Moore, R. L.↗
NASA NTRS1972

Tensile properties of PRD-49 fiber in epoxy matrix.

Recently a high-modulus and high-strength organic fiber, identified as PRD-49-III by the manufacturer, became commercially available. To assess the fiber performance and its potential as a reinforcement for fiber composites, the tensile properties of the fiber in an epoxy matrix were determined. During this study over 6000 fiber/epoxy strands were made using the filament winding process; these strands were representative samples taken from over 60 lb of single-end fiber. The fiber uniformity, its strength distribution at room and LN2 temperature, stress-strain characteristics, and the strain rate effect on the fiber strength were evaluated.

Chiao, T. T.↗