Engineering topics

Steinitz, R.

Publications and source records attributed to Steinitz, R..

4 records

NASA NTRS1977

The embedded feature model for the interpretation of chromospheric contrast profiles

Contrast profiles obtained from chromospheric filtergrams and spectra of bright and dark mottles have to date been interpreted almost exclusively in terms of Becker's cloud model. Here we demonstrate the failure of this model to account in a physically consistent way for the observed contrasts. As an alternative, we introduce an embedded-feature model, restricting our discussion in this paper to stationary features. Our model is then characterized by three independent parameters: the density of absorbing atoms, the geometrical depth, and the profile of the absorption coefficient. An analytic approximation to the contrast resulting from such a model reproduces well the observed behavior of all types of contrast profiles.

Steinitz, R.↗

NASA NTRS1974

On spatial variations in the intensity of chromospheric H-alpha

Investigation of the formation of patterns in H-alpha spectroheliograms and filtergrams. Introducing a source-sink-control diagram, it is concluded that the H-alpha line source function in the quiet solar chromosphere is indirectly controlled by the photospheric radiation fields in the Balmer and Paschen continua. It is demonstrated that in producing the observed patterns, horizontal spatial variations in the shape of the absorption profile are extremely effective compared to changes in the source and sink terms. Applying this mechanism, asymptotic values are computed for the contrasts and visibilities in chromospheric H-alpha.

Gebbie, K. B.↗

NASA NTRS1973

A mechanism for the production of light and dark contrasts in radiatively controlled lines.

It is shown that light and dark contrasts observed in the radiation of strong lines may arise from lateral differences in the local value of the scattering term alone, independently of the local values of temperature and pressure. Mechanisms for the production of such differences are suggested, and regions are pointed out in which they occur as 'features.' From numerical examples presented, it is seen that the effect of such features on the emergent radiation field is determined by their position with respect to the shape of the source function.

Gebbie, K. B.↗

NASA NTRS1973

On the dependence of the two-level source function on its radiation field.

The consequences of the universally made assumption that the stimulated emission profile is identical to the absorption profile are quantitatively investigated for a two-level atom with Doppler redistribution. The nonlinear terms arising in the source function are evaluated iteratively. We find that the magnitude of the effects is probably completely negligible for visible and UV solar lines.

Steinitz, R.↗