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1.
Using slab model atmospheres that are irradiated from both sides by photospheric, chromospheric, and coronal radiation fields we have determined the ionization and excitation equilibrium for hydrogen.The model atom consists of two bound levels (n = 1 and n = 2) and a continuum. Ly- was assumed to be optically thick with the transition in detailed radiative balance. The Balmer continuum was assumed to be optically thin with the associated radiative ionization dominated by the photospheric radiation field (T
rad = 5940 K). The ionization equilibrium was determined from an exact treatment of the radiative transfer problem for the internally generated Ly-c field and the impressed chromospheric and coronal field (characterized by T
rad = 6500K).Our calculations corroborate the hypothesis that N2, the n = 2 population density, is uniquely determined by the electron density N
e. We also present ionization curves for 6000K, 7500K, and 10000K models ranging in total hydrogen density from 1 × 1010/cm3 to 3 × 1012/cm3. Using these curves it is possible to obtain the total hydrogen density from the n = 2 population density in prominences and spicules.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
2.
Observations of a sunspot in the Civ line at 1548 Å formed in the transition region have been analyzed to obtain the time variations and/or mean values of the velocity, intensity, longitudinal magnetic field, and line width. Oscillations with periods between approximately 110 and 200 s are observed only over the umbra where the transition region magnetic field is highest and the line width is smallest. When periodic intensity variations occur at the same frequency as the velocity oscillations, the peak intensities occur slightly before the maximum upward motions. No periodic variations in the transition region magnetic field have been detected. Scatter diagrams are presented which show possible relationships between the flow velocity, emission line intensity, line width, and transition region magnetic field. 相似文献
3.
Populations for the first three bound states and the continuum of hydrogen are determined for an isothermal, hydrostatic atmosphere at 20 000 K. The atmosphere is treated as being optically thin in the Balmer and Paschen continua and illuminated by continuum radiation at these wavelengths with prescribed radiation temperatures. The atmosphere is optically thick in the 2-1, 3-1, 3-2 and c-1 transitions. Three stages of approximation are treated:
- radiative detailed balance in the 2-1, 3-1 and 3-2 transitions,
- radiative detailed balance in the 3-1 and 3-2 transitions, and
- all transitions out of detailed balance.
4.
SMM data from the Corograph/Polarimeter experiment giving intensities of H and continuum emission in eight erupting prominences are analyzed to obtain the physical conditions in the regions of H emission. Since the H intensity depends upon three unknowns whereas only two independent observations are available, it is necessary to assume one additional condition in order to obtain unique solutions. Solutions are chosen that give the maximum expansion of the prominence volume as reflected by minimum values of the electron density. These solutions correspond closely with those giving the best agreement between the gas pressure in the prominence and the ambient coronal pressure. Electron densities are found to be of the order of 108 cm-3 at temperatures near 2 × 104 K.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation. 相似文献
5.
Gradients of H and electron scattering intensities derived from instantaneous radial distributions of erupting prominence material observed at several solar radii by Illing and Athay (1986) are often markedly smaller than those inferred by comparing the intensities observed near several radii to average prominence intensities observed near the limb. In this paper, we show that gradients derived by following individual features in their outward progression with time yield values that are consistent with limb observations and that usually exceed the values obtained from instantaneous distributions. We conclude from the diversity of observed gradients that the prominence eruption cannot be described by a self-similar expansion in which the expansion velocity is a function of radius and time only. However, we cannot rule out possible self-similar solutions that allow the expansion velocity to be a function of angular direction.On leave from the Astronomical Observatory of Wrocaw University, Poland.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation. 相似文献
6.
Qualitative arguments are presented to show that in the chromosphere-corona transition region the energy which is transported downwards by heat conduction cannot be disposed of by radiative losses only. The region therefore is unstable and forced to be in motion, which may give rise to spicule-like phenomena.On leave from the Observatory Sonnenborgh at Utrecht, The Netherlands. 相似文献
7.
R. G. Athay 《Solar physics》1970,12(2):175-185
Profiles are computed for Ha and two Fei lines for a differentially moving atmosphere. The results show that the profiles are asymmetric and that velocity measurements made in the Doppler cores will often lead to erroneous results when the velocity gradient is significant in the regions of the atmosphere where the core forms.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
8.
R. Grant Athay 《Solar physics》1984,93(1):123-131
A number of properties of EUV bursts are found to be consistent with the conclusion that they are at the low energy extreme of the family of events including flares. The incidence of EUV bursts exceeds that of flares by over two orders of magnitude, which suggests the possibility that, in total, they may be as important energetically as flares. The faster EUV bursts have light curves resembling those observed in hard X-rays at the times of flares.The National Center for Atmospheric Research is Operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation. 相似文献
9.
R. Grant Athay 《Solar physics》1988,116(2):223-237
An attempt is made in this paper to determine the coefficient a in a power-law relationship of the form V
~T
between the r.m.s. velocity fluctuation, V
for raster images with 3 resolution and the temperature, T of line formation using SMM solar data. For T between 8000 and 105 K, the data suggest a best fit with 3/4 < 1. It is argued, however, that unresolved fine structure tends to reduce the observed value of V
and that higher resolution data may yield different values for . Skylab data have shown that the non-thermal line broadening velocity, , is proportional to T
1/2. Also, for all temperatures less than 105 K, V
. This latter result, however, is again dependent on spatial resolution and may not be true in observations made with sufficient spatial resolution. The magnitudes of both V
and indicate that bulk motions play important roles in the structure of the solar atmosphere as well as in its energy and momentum balance. It is important, therefore, to identify the true nature of such motions with better accuracy than is possible with currently available data.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
10.
R. Grant Athay 《Solar physics》1973,29(2):357-364
Mean density models of the solar corona show evidence for two distinctive density regimes characterized by different density gradients. High density gradients are identified with regions of predominantly open magnetic lines of force and low density gradients are identified with regions of predominantly closed magnetic lines of force. Spectroscopic data yielding equivalent widths of forbidden lines of Fe x and Fe xiv strongly suggest that the coronal temperature for r > 2.5 R
decreases considerably less rapidly in equatorial regions than r
–2/7, which is the decrease predicted by conduction models with open field lines.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献