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Acton, L. W.

Publications and source records attributed to Acton, L. W..

90 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Cooling of solar flare plasmas

A model for the cooling of solar flare plasmas is considered that makes allowance for atmospheric readjustments and is so formulated that the effects of conduction on the emission measure are evident. This model shows that an increasing emission measure with decreasing temperature is a characteristic feature of those solar flares for which expansion of the cooling volume is negligible. A similar but slower increase in emission measure with decreasing temperature results from pure radiative cooling if the hot region remains isothermal.

Zaumen, W. T.↗
NASA NTRS1974

The solar X-ray spectrum

The characteristics of X-ray emission from the normal corona are considered, giving attention to questions of spatial and spectral distribution. Aspects of X-ray emission from solar flares are also investigated. Details of X-ray spectroscopy for coronal plasma diagnosis are discussed, taking into account techniques, the diagnosis of equilibrium plasmas, and the diagnosis of nonthermal events. The study of continuum emission and line emission is reported along with investigations of departures from equilibrium.

Culhane, J. L.↗
NASA NTRS1972

Experimental study of spectral and spatial distribution of solar X-rays

The study of the physical conditions within the solar corona and the development of instrumentation and technical expertise necessary for advanced studies of solar X-ray emission are reported. Details are given on the Aerobee-borne-X-ray spectrometer/monochromator and also on the observing program. Preliminary discussions of some results are presented and include studies of helium-like line emission, mapping O(VII) and Ne(IX) lines, survey of O(VII) and Ne(IX) lines, study of plage regions and small flares, and analysis of line emission from individual active regions. It is concluded that the use of large-area collimated Bragg spectrometers to scan narrow wavelength intervals and the capability of the SPARCS pointing control to execute a complex observing program are established.

Acton, L. W.↗
NASA NTRS1972

Coronal survey in X-rays of O VII and Ne IX.

Results of a rocket experiment flown on Apr. 29, 1971, in which a survey of the solar corona was carried out with a pair of collimated Bragg spectrometers to study the resonance, intersystem, and forbidden line emission from the helium-like ions O vii (22 A) and Ne ix (13 A). The observed X-ray emission came from the general corona, seven plage regions, and one dynamic feature - the late stage of a small flare. From the intensity of the O vii and Ne ix resonance lines the electron temperature and emission measure of the individual emitting regions are derived on the basis of two models, one in which the region is assumed to be isothermal and another in which the emission measure decreases exponentially with increasing temperature. The latter model, which is the most adequate of the two, yields for the electron temperature of the time-varying feature 2,000,000 to 3,000,000 K, for the other active regions 1,500,000 to 2,500,000 K, and for the general corona 1,300,000 to 1,700,000 K. The Ne ix emitting regions are about 1.5 times as hot as the O vii regions.

Acton, L. W.↗
NASA NTRS1972

X-ray study of solar plage regions and a small flare.

The O VII and Ne IX resonance line and 5 keV continuum emission of a small solar flare are interpreted on the basis of a model in which the emission measure of the region is an exponentially decreasing function of temperature. Good agreement with all three sets of data is obtained - a result not possible on the basis of an isothermal approximation. The change in the emission of the flare over a two minute interval appears to be consistent with a simple cooling of the region. Computation of the contribution function versus temperature for each emission indicates that each predominantly comes from a physically separate volume within the feature. The emission measure distribution for the flare is distinctly flatter than that of five plage regions which tend to have similar slopes and which are in turn flatter than the general corona.

Acton, L. W.↗
NASA NTRS1970

X-ray photometry of M1

M1 X ray emission, examining energy interval and power law spectral distribution

Acton, L. W.↗
NASA NTRS1967

X-ray spectra of several cosmic sources.

X-ray spectral distributions and fluxes in low kev range of five cosmic sources at low galactic latitude and longitude, noting effective temperature

RADIATION DETECTOR↗