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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Intensity oscillation in H alpha-fine structures

Using a new technique of directly measuring the intensity variation from the 16mm time-lapse filtergram movies taken in the blue wing and in the line center of H-alpha, periodic intensity oscillations were found in the center of H-alpha supergranulation network, in rosette centers, and in plage granules. The oscillatory period of intensity in the network is of the order of 170 + or - 44 seconds while in regions of stronger magnetic field, such as in plages and in rosettes, the period was found to be longer, on the order of 300 + or - 50 seconds. It is suggested that observed intensity oscillation in the rosette center is related to the shooting out of dark mottles from rosettes. Oscillatory intensity fluctuations were also observed in the sunspot umbra.

Bhatnagar, A.↗
NASA NTRS1971

H alpha fine structure and the chromospheric field.

Study of the physical characteristics of the H alpha structures previously defined as fibrils and threads. The interpretation of the fibrils as ends of flux tubes is useful in tracing the behavior of the transverse field component over the solar surface. The observed properties of fibrils and threads are consistent with the hypothesis that they are produced by a shock wave mechanism similar to that advanced by Parker (1963) to explain spicules. It is suggested that the undisturbed magnetic field in the chromosphere of an active region is confined to a thin sheath, while the field of the quiet regions extends into the corona.

Foukal, P.↗
NASA NTRS1972

Fine structure of solar magnetic fields.

Extension of the deduction of magnetic fields from chromospheric structure to active regions and transverse fields. Fields independently predicted by these rules from a high-resolution H alpha filtergram are compared with a high-resolution magnetogram. The H alpha method has the advantage over conventional magnetograms that it shows transverse fields and relates the fields to the real sun. It has the disadvantage that higher spatial resolution is required and that it is difficult and time consuming in very complicated regions. The response of the chromosphere to magnetic fields is most consistent. Vertical field is invariably marked by bright plage, with brightness roughly proportional to the field strength (except for sunspots). All dark fibrils mark transverse fields and are parallel to field lines. All polarity changes are marked by dark fibrils, which may be transverse fibrils perpendicular to the field boundary, or filaments (prominences) which connect more distant points, and in which the field lines run nearly parallel to the boundary. The asymmetry between preceding and following polarity found by Veeder and Zirin (1970) does not exist; it was due to the low resolution of the Mount Wilson magnetograms.

Zirin, H.↗
NASA NTRS1972

Intensity oscillation in H-alpha fine structure.

Using a new technique of directly measuring the intensity variation from the 16 mm time-lapse filtergram movies taken in the blue wing and in the line center of H-alpha, we found periodic intensity oscillations in the center of H-alpha supergranulation network, in rosette centers and in plage granules. The oscillatory period of intensity in the network is of the order of 170 plus or minus 44 seconds while in regions of stronger magnetic field, such as in plages and in rosettes, the period was found to be longer, on the order of 300 plus or minus 50 seconds. It is suggested that observed intensity oscillation in the rosette center is related to the shooting out of dark mottles from rosettes. Oscillatory intensity fluctuations have been also observed in the sunspot umbra.

Bhatnagar, A.↗
NASA NTRS1972

Fine structure in H II regions - Synthesis observations at 11 and 3.7 centimeters.

New high-resolution observations of several H II regions are reported. Improved values for the physical parameters describing the structure are deduced from their continuum spectra. The results are compared with estimates obtained by other means. The data are found to agree surprisingly well with the results of Andrews et al. (1971). The relation between the structure and the parent H II region is also investigated.

Balick, B.↗
NASA NTRS1972

Fine structure of the lower atmosphere as seen by high resolution radar

A ground-based vertically pointing FM-CW radar is described that permits remote probing of the refractive index structure in the troposphere. The radar has the characteristics of extremely high sensitivity, ultrahigh range resolution, and close minimum detection range without clutter. The sounder routinely detects layer structures in the lower troposphere. These layers are always associated with gradients in the vertical refractive index profile, and are frequently very thin, approaching the resolution of the radar (1 m). Very often they are perturbed by wave motions. Examples of various wave patterns are presented, and an explanation is given for organized substructures frequently superimposed on larger scale wave motions.

Richter, J. H.↗
NASA NTRS1973

Electric field and fine structure in aurora.

Simultaneous rocket measurements of electric field and optical aurora during a weak PCA event are presented. The aurora consisted of faint structures superposed on a homogeneous glow, and on-board photometers showed that the rocket passed through two discrete auroral forms. These enhanced auroral emissions coincided with variations in the dc electric field and an increase in the ac field. A detailed comparison between electric fields and optical emissions shows that the relation is quite complex. The results are compared with earlier electric field and optical auroral measurements.

Maseide, K.↗
NASA NTRS1974

The fine structure of the solar atmosphere in the far ultraviolet

The paper describes qualitatively the spatial distribution of UV emission obtained from high resolution spectroheliograms in the UV emission lines He I, He II, O IV, O V, and Ne VII photographed during a sounding rocket flight. Broad band filtergrams of the far UV solar corona were also obtained. The results confirmed that spicules are the location of UV emission. Most of the UV emission in the temperature range from 100,000 to 200,000 K is concentrated in and around the spicules and this concentration decreases with increasing temperatures. Four different areas of UV emission are discussed. The He I and He II spectroheliogram observations showed He to be suppressed in the coronal holes, polar caps, and sunspots.

Brueckner, G. E.↗