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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 397 records · Page 22
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NASA NTRS1973

Solar rotation in the chromosphere and corona

Extreme ultraviolet spectroheliograms in Mg X (625 A) and the Lyman continuum (897 A) obtained from OSO-6 are used to determine the differential rotation rate in the solar chromosphere and corona. The equatorial rotation rate agrees with spectroscopic measurements of the photospheric plasma velocity; the variation of rate with latitude is less pronounced than in most other determinations. We cannot discern a variation in the rotation rate between the chromosphere and corona.

Henze, W., Jr.↗
NASA NTRS1974

A comparison of EUV spectroheliograms and photospheric magnetograms

A comparison of EUV data from an experiment on the OSO-6 satellite with photospheric magnetograms from Kitt Peak National Observatory indicates relationships between the strength of the photospheric magnetic field and density in the overlying corona in quiet and in active regions, distinctly differing from previous notions. In addition, the photospheric field beneath a coronal hole is found to be virtually identical to that beneath normal quiet regions.

Gurman, J. B.↗
NASA NTRS1974

Observations of solar X-ray bursts in the energy range 5-15 keV

Bursts of solar X-rays in the energy range 5-15 keV are associated with flares and are due to thermal emission from a hot coronal plasma. The results of the first study of a large sample of separate bursts, 197 events associated with subflares, and of a few events of importance 1 are presented. The observations were made by a proportional counter on the satellite OSO-7 from October, 1971 to June, 1972. In most cases, the temperature characterizing the X-ray spectrum rises impulsively at the onset of the burst and then declines slowly throughout the remainder of the burst. The emission measure rises exponentially with a time scale of 30-100 sec and then declines slowly on a time scale of the order of 1,000 sec. It is shown that the growth of the thermal energy in the flare plasma throughout the burst can be due to the heating of new cool material.

Datlowe, D. W.↗
NASA NTRS1974

Is the zodiacal light intensity steady

It is pointed out that conclusions reported by Sparrow and Ney (1972, 1973) could be confirmed in an investigation involving the refinement of OSO-5 data on zodiacal light. It had been found by Sparrow and Ney that the absolute value of both the surface brightness and polarization of the zodiacal cloud varied by less than 10% over the 4-yr period from January 1969 to January 1973.

Burnett, G. B.↗
NASA NTRS1974

Solar-flare emission lines in the range from 66 to 171 A; 2sr 2pk - 2s/r-1/ 2p/k+1/ transitions in highly ionized iron

New emission lines found in several flare spectra obtained with the Goddard grating spectrometer on the OSO-5 satellite, in 1969, have been listed by wavelength and relative intensity. These new lines, including several as strong as normal quiet-sun lines, are extremely variable in intensity and have been assigned mainly to transitions of the type 2sr 2pk - 2s(r-1) 2p(k+1) in iron ions up to Fe XXIII.

Kastner, S. O.↗
NASA NTRS1974

X-ray observations of the supernova remnant IC 443

Presented observation data from OSO-7 are shown to confirm the identification of IC 443 as an X-ray source, with a spectrum which is consistent with either thermal bremsstrahlung or a power law. These data lead to an age of 3400 years for IC 443, much younger than previous estimates.

Winkler, P. F., Jr.↗
NASA NTRS1974

Search for gamma ray lines from supernovae and supernova remnants

A gamma ray monitor with a NaI crystal shielded with a cup-shaped CsI cover was contained in the rotating wheel compartment of the OSO-7 spacecraft for measuring the gamma ray spectra from 0.3 to 10 MeV in search for gamma ray lines from a possible remnant in the Gum Nebula and the apparent Type I supernovae in NGC5253. A brief analysis of data yielded no positive indications for X-rays, gamma ray lines, or continuum from these sources.

Chupp, E. L.↗
NASA NTRS1974

Solar coronal holes as sources of recurrent geomagnetic disturbances

Observations of the solar corona by Oso 7 have been used in a superposed epoch analysis to study the relationships between classes of coronal features and geomagnetic activity. Both bright coronal regions and regions of less than average brightness were investigated. It was found that for the period from January 1972 through January 1973, a significant enhancement in geomagnetic activity occurred 2-3 days after central meridian passage of large coronal holes that extended to within 5 deg of the solar subearth point when they were on the meridian. Large coronal holes appear to satisfy the requirements for 'M regions' which were hypothesized to be responsible for recurrent geomagnetic disturbances (Bartels, 1934). If solar wind high-speed streams originate preferentially in these regions, their velocity at the base of the corona will be substantially higher than that expected from an axisymmetric solar wind model.

Neupert, W. M.↗
NASA NTRS1974

Coordinated rocket and satellite observations of the solar corona

Coronal condensations associated with active regions are investigated by comparing their X-ray and EUV line intensities. The EUV line measurements were made with the OSO-H satellite, and the X-ray measurements were made with an ATM support rocket. The data obtained from these observations are used to find the emission measure distribution at low temperatures.

Zaumen, W. T.↗
NASA NTRS1975

Solar and terrestrial physics

The effects of solar radiation on the near space and biomental earth, the upper atmosphere, and the magnetosphere are discussed. Data obtained from the OSO satellites pertaining to the solar cycle variation of extreme ultraviolet (EUV) radiation are analyzed. The effects of solar cycle variation of the characteristics of the solar wind are examined. The fluid mechanics of shock waves and the specific relationship to the characteristics of solar shock waves are investigated. The solar and corpuscular heating of the upper atmosphere is reported based on the findings of the AEROS and NATE experiments. Seasonal variations of the upper atmosphere composition are plotted based on OGO-6 mass spectrometer data.

Source record↗
NASA NTRS1975

Slow X-ray bursts and chromospheric flares with filament disruption

The data from OGO-5 and OSO-7 X-ray experiments have been analyzed to study six chromospheric flares with filament disruption associated with slow thermal X-ray bursts. Filament activation accompanied by a slight X-ray enhancement precedes the first evidence of H alpha flare by a few minutes. Rapid increase of the soft X-ray flux is accompanied by a sudden brightening of the filament when viewed on-band H alpha. Thereafter the bright chromospheric strands reach their maximum brightness with maximum X-ray flux. Any plateau or slow decay phase in the X-ray flux is accompanied by a quieting in filament activity and even by filament re-appearance. The height of the disrupted prominence is proportional to the soft X-ray flux for the August 3, 1970 limb occulted event.

Roy, J. R.↗
NASA NTRS1975

Solar X-ray studies

The hard X-ray component in the impulsive phase of solar flares is reported. Observations from OGO-5 OSO-7 show no center-to-limb effect of soft X-ray flare. These soft events were plotted separately as a function of solar longitude.

Vorpahl, J. A.↗
NASA NTRS1974

Gamma ray observations during the August 1972 solar activity

During the solar activity period in August 1972, the UNH gamma ray monitor on the OSO-7 satellite measured gamma ray line and continuum fluxes of solar origin on at least two occasions; August 4 and 7. In this discussion, the experiment and the gamma ray line observations are reviewed with a few brief remarks on interpretation. The specific observations discussed are measurements of gamma ray lines at 0.51 and 2.2 MeV during two of the largest optical solar flares. Evidence for lines at other energies is also given.

Chupp, E. L.↗
NASA NTRS1975

Counterglow from the earth-moon libration points

Results from the OSO-6 Rutgers Zodiacal Light Analyzer experiment show photometric perturbations above the background in the antisun line of sight. Sixteen successive lunations were examined, and the accumulated perturbations show a maximum value in the direction of the L4 and L5 earth-moon libration points. This is interpreted as a counterglow from a cloud of particles at the libration points. The average brightness of these libration clouds is 20 S10 Vis. The average angular size of the libration clouds is approximately 6 degrees. Their position varies from one lunation to the next, within an ellipsoidal zone centered on the libration-point direction, with its semimajor axis, of approximately 6 degrees, nominally in the ecliptic and its semiminor axis, of approximately 2 degrees perpendicular to the ecliptic. The position of these clouds with respect to the Lagrangian L4 and L5 points is towards the moon in the northern summer and away from the moon in the northern winter.

Roach, J. R.↗
NASA NTRS1975

X-ray bursts from solar flares behind the limb

Data from the OSO-7 X-ray experiment were used in a search for behind-the-limb solar X-ray bursts. Seventeen active centers were found as likely seats of such bursts. The spectra of 37 over-the-limb X-ray bursts were analyzed. The distributions of maximum temperature, maximum emission measure, and characteristic cooling time do not differ in a statistically significant way from the distributions for center events. The observations support the view that the dominant cooling mechanism is conduction, for the cooling times derived from the temperature histories are too small to be explained by radiative cooling. The fraction of over-the-limb bursts which have an nonthermal component is 2/3, exactly the same as found for the 122 X-ray bursts studied in Datlowe et al. (1974b). Thick-target models of X-ray emission would suggest that hard X-ray sources would be rapidly occulted with increasing longitude of the burst location, yet just the contrary was observed.

Roy, J.-R.↗
NASA NTRS1975

Hard X-ray bursts from flare behind the solar limb

The determination of the location of the region of origin of hard X-rays is important in evaluating the importance of 10-100 keV electrons in solar flares and in understanding flare particle acceleration. At present only limb-occulted events are available to give some information on the height of X-ray emission. In fifteen months of OSO-7 operation, nine major soft X-ray events had no reported correlated H alpha flare. We examine the hard X-ray spectra of eight of these events with good candidate X-ray flare producing active regions making limb transit at the time of the soft X-ray bursts. All eight bursts had significant X-ray emission in the 30-44 keV range, but only one had flux at the 3 sigma level above 44 keV. The data are consistent with most X-ray emission occurring in the lower chromosphere, but some electron trapping at high altitudes is necessary to explain the small nonthermal fluxes observed.

Mckenzie, D. L.↗
NASA NTRS1975

Upper limits of hard gamma-ray emission from six X-ray sources

The Cornell 100-inch gamma-ray telescope has been used to set upper limits for the gamma-ray flux above 400 MeV from the X-ray sources Cyg X-1, Cyg X-2, Cyg X-3, Cas A, Cas B, and Per X-1. An upper limit for the diffuse flux of the galactic disk was set which is consistent with OSO-3 and SAS-2 data. A new measurement of the atmospheric gamma-ray generation rate is presented.

Campbell, M.↗