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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Optical and radio observations for the BL Lacertae objects 1219 + 28, 0851 + 202, and 1400 + 162

Radio- and visible-wavelength observations for the BL Lac object 1219 + 28 (ON 231, W Com) are reported along with optical observations of 0851 + 202 (OJ 287), and radio data for 1400 + 162 (4C 16.39, OQ 100). The obtained data consist of imaging and surface photometry for both 1219 + 28 and 0851 + 202, as well as spectra for 1219 + 28, and Very Long Baseline Interferometry (VLBI) observations for 1219 + 28 and 1400 + 162. Two emission features have been observed in the spectrum of 1219 + 28. Radio observations of 1219 + 28 in three frequencies reveal the presence of a radio jet with at least three components. The obtained results for 1219 + 28 support previous conclusions that at least some BL Lac objects are located at the center of elliptical galaxies.

Weistrop, D.↗
NASA NTRS1971

A discussion of the ground-based radio observations

It is reasserted that the Gum nebula is not a single nebula but appears to be composed of several different entities. All the surveys of the southern sky in the continuum, recombination line, H I, and OH were considered. The large amount of high frequency radio emission from the small nebula is noted. The outer part of the Gum nebula has not been seen in any radio observations so far. Only the inner part has been observed to date. It is not justifiable to work out any parameters for the whole nebula by taking an average over the whole solid angle subtended by the big nebula. There appears to be a large difference in density between the small nebula and the big one.

Kerr, F. J.↗
NASA NTRS1977

A study of filament transition sheath from radio observations

An H-alpha dark filament has been observed at 8, 15 and 22 GHz, and its radio spectrum derived. It is suggested that the filament may be optically thick at radio frequencies and that the observed spectrum may be due to the presence of a transition sheath surrounding the filament. A model is developed for the transition sheath in which the energy radiated away is balanced by the conduction of heat from the corona; the radio observations indicate that little or no thermal energy is conducted into the main body of the filament. The model is compared with ultraviolet observations of filaments.

Rao, A. P.↗
NASA NTRS1988

Radio observations of SN 1987A

The study of radio emission from SN 1987A after the neutrino burst is reviewed. The observed maximum flux density of the burst at radio wavelengths was about 140 mJy and occurred at 1.4 GHz. The radio light curves for SN 1987A at four frequencies are compared with data for SN 1979C and SN 1980K. VLBI observations of SN 1987A at 2.3 GHz and other radio monitoring programs are examined.

Bartel, N.↗
NASA NTRS1987

Radio observations of carbon monoxide toward Zeta Ophiuchi - Velocity structure, isotopic abundances, and physical properties

This paper presents a small-scale map of the molecular gas around the line of sight toward Zeta Oph made with measurements of the (C-12)O (1-0) emission obtained at high signal-to-noise ratio and high velocity resolution. In addition, a measurement of the (C-12)O (2-1) line emission and a detection of (C-13)O along the line of sight to the star are reported. The results show that the CO emission toward the star is composed from at least four components with peak velocities at -2.0, -0.7, 0.0, and +0.6 km/s. The radio observations yield a total CO column density of 1.4 x 10 to the 15th/sq cm, with about one-half of the total CO column density being in the main component at -0.7 km/s. The main cmponent is uniform over the map, but the other components are variable, suggesting that the cloud is clumpy. The data on the two CO transitions imply that the excitation temperature and the density of the main component are about 7 K and 800/cu cm, respectively.

Langer, William D.↗
NASA NTRS1978

X-ray and radio observations of GX 17+2 and GX 13+1

X-ray data on the sources 3U 1813-14 (GX 17+2) and 3U 1811-17 (GX 13+1), obtained by Copernicus between 1975 and 1977, are examined. These reveal correlated intensity and spectral-slope variations in GX 17+2 similar to those seen in Sco X-1 and four other galactic sources, 3U 0614+09, 3U 1702-36, 3U 1728-16, and 3U 1758-25. The data on GX 17+2 have been unsuccessfully searched for further evidence of a shallow 31.9-minute modulation. In the case of GX 13+1 no significant variability was seen in either intensity or spectrum. A simultaneous search made from the NRAO simultaneously with some of the X-ray observations revealed no significant radio emission from either source.

White, N. E.↗
NASA NTRS1976

Earth-based radio observations of Jupiter - Millimeter to meter wavelengths

The historical development of the study of Jupiter radio emission is considered and a description of the observational data is presented, taking into account the spectrum of the continuous microwave radiation, the polarization of the microwave radiation, the brightness distribution, the rotation-related variability, variations related to the zenocentric declination of the earth, and other time variations. The separation of radio emission into thermal and nonthermal components is discussed and interpretations of the two components are provided. A comparison of earth-based radio measurements with Pioneer 10 and 11 data is conducted and the future of earth-based radio observations is evaluated.

Berge, G. L.↗
NASA NTRS1989

Evidence of CO2-induced progressive cooling of the middle atmosphere derived from radio observations

Reflection heights of low frequency radio waves in midlatitude summer, which are closely associated with the neutral atmosphere isobaric level of 0.0052 hPa, exhibit a statistically significant downgoing trend from 1962 to 1987. This indicates a systematic decrease of air pressure at 80 km height by 10.3 plus or minus 4.9 percent over this period, to be regarded as a sufficient evidence of a true signal of progressive cooling of the middle atmosphere, expected with the growing content of CO2 and other greenhouse bases in the atmosphere. It is quantitatively consistent with a temperature decrease at the stratopause by about 4 K, as predicted by the recent model of interactive greenhouse and ozone processes of Brasseur and de Rudder (1987).

Taubenheim, J.↗
NASA NTRS1995

Ulysses-ARTEMIS radio observation of energetic flare electron

Type 3 radio bursts allow us to follow energetic electrons ejected by solar flares into the interplanetary medium, even when the observer is far away from the electrons. The emission frequency f(sub p) is related to the ambient density n(sub e) by f(sub p) varies as the square root of n(sub e), and as a function of the distance r to the sun we have approximately n(sub e) varies as r(exp -2); as a consequence, on a 1/f - t dynamic spectrum type 3 bursts appear as nearly straight traces, whose slope gives an estimation of the source speed. We used the data of the URAP radio receiver on Ulysses (1-1000 kHz), observing sources in the solar wind, and the ground data of the ARTEMIS spectrograph (100-500 MHz), observing sources of the corona, over the years 1991-1994. We found a surprisingly large number of excellent high-frequency - low-frequency associations. A type 3 burst group on ARTEMIS (10 to 100 bursts over 1 to 10 minutes) typically gives rise to one isolated burst on Ulysses. As bursts often start in high frequencies during the maximum phase of flares, this demonstrates in a very convincing manner that some of the flare electrons themselves make it all the way to the interplanetary medium. We discuss decorrelation cases in the context of geometrical configuration between the active region and the two observing sites. We also study how apparent electron speeds vary with the distance to the sun.

Hoang, S.↗
NASA NTRS1995

Ulysses radio observations of the heliospheric activity in early June 1991

The radio receiver of the URAP (Unified Radio and Plasma Wave) experiment on Ulysses has recorded a heliospheric activity particularly intense between late May and early June 1991. Many solar radio emissions of types III and II were observed together with interplanetary (IP) shocks. In the same time, the radio spectrograph ARTEMIS at Nancay (France) observed several intense type II bursts. We investigate the association and/or interaction of these radio emissions, which are remotely observed, with some IP shocks detected in situ, in the context of a Coronal Mass Ejection (CME) induced scenario.

Hoang, S.↗
NASA NTRS1977

Structure of coronal holes from UV and radio observations

EUV (Fe XV at 284 A) and radio (at 169 and 408 MHz) observations were made of the coronal hole on May 31, 1973. An inhomogeneous model consisting of hot (a temperature of about 2 x 10 to the 6th K) elements covering 10% of the hole surface surrounded by regions of colder gas (a temperature of about 8 x 10 to the 5th K) is able to explain both observations.

Drago, F. C.↗
NASA NTRS1974

Solar radio observations in support of Skylab A

The solar radio spectra were recorded in real time, both on film and magnetic tape, during the period from November 1972 to February 1974. A catalogue of the observations is given for the frequency range 565-1000 MHz and includes descriptions of the bursts, intensity scales, and pertinent remarks. Some theoretical considerations resulting from the research are given. Equipment modified for the experiment is described and the text of the final report which summarizes the research on type IV solar radio bursts is included.

Gotwols, B. L.↗
NASA NTRS1991

Evidence of auroral plasma cavities at Uranus and Neptune from radio burst observations

Radio bursts originating from the stronger magnetic polar regions of both Uranus and Neptune were detected by the planetary radio astronomy experiment during the Voyager 2 encounters with the planets. It has previously been demonstrated that these bursts are beamed into a broad, hollow emission pattern from their auroral sources. It is now shown that the bursts at both planets also manifest similar detailed patterns, with the waves beamed into two separate and distinct radiation cones at intermediate wave frequencies. This double-cone emission pattern is predicted by relativistic cyclotron resonance theory, and application of this theory to the observed emission pattern yields the plasma density structure within the radio source region. Calculations indicate that at both Uranus and Neptune the plasma-to-cyclotron frequency ratio can drop well below 0.01 within the active region. Such low values indicate that the southern auroral zones at both planets contain an auroral plasma cavity that is similar to that found in earth's nightside auroral zone.

Farrell, W. M.↗
NASA NTRS1978

Decameter-wave radio observations of Jupiter during the 1977 apparition

A catalog of observations of Jupiter's sporadic decameter wavelength radio emissions obtained with the Goddard Space Flight Center Jupiter Monitor Network between June 1977 and May 1978 is presented. Data were collected using the Goddard Space Flight Center station in Greenbelt, MD. and at facilities installed at Orroral Valley (Canberra), Australia and the Nancay Radio Observatory in France. Observations were obtained daily at frequencies of 16.7 and 22.2 MHz using five-element Yagi antennas at each end of a two-element interferometer. Plots of the two dimensional emission occurrence probability distribution are given.

Alexander, J. K.↗
NASA NTRS1986

Voyager 2 radio observations of Uranus

Voyager 2 detected continuous radio signals in the 40-100 kHz interval starting from 5 days before passage of Uranus. The radio signals reached 800 kHz within 4 days of closest approach and continued throughout the outward bound phase of flight. The signals were modulated with a period close to 17.24 days, the same period calculated for the rotation of the Uranus magnetosphere with other spacecraft data. The planet was also found to have an off-center magnetic field, and radio signals were strongest when the dipole center was on the nightside of Uranus. Dynamic spectral and burst events which were recorded indicated that Uranus, like the earth, has a strongly defined plasmasphere. It moves under the control of magnetic force tubes that interact with the magnetosphere boundary, producing a variety of MHD phenomena.

Warwick, J. W.↗