共查询到20条相似文献，搜索用时 46 毫秒
1.
The brightness distribution of the quiet Sun at 8.6 mm wavelength is synthesized from off-meridian observations using an eight element east-west interferometer with a maximum base line of 16.38 m (1913). The observed brightness distribution is practically flat from the disk center to the optical limb. The effective radius of the nearly uniform component is 1.01 R
. If the limb brightening is present, the brightening located between 0.95 R
and 1.01 R
, and the total flux density of the limb brightening is less than 1% of the total flux density of the Sun. In addition to the nearly uniform component there exists a coronal component just outside the optical limb. 相似文献
2.
Spectrographic observations of the flash spectrum were made by the Kwasan Observatory at the total solar eclipse on 7 March, 1970. The integrated intensities of Fexiv 5303, Fex 6374, and the continuum were measured on the spectrograms as a function of height above the Sun's limb. It was found that a large amount of emission in the coronal lines originates in the interspicular regions of the chromosphere. Analysis of the data yielded that the interspicular regions consist of coronal material of T
e = 1.6 × 106–1.2 × 106 and log N
e = 8.5–9.5, and that a decrease in T
e and an increase in N
e occur with decreasing height. 相似文献
3.
K. A. Marsh 《Solar physics》1978,57(1):37-48
High resolution filtergrams of the solar limb in D3 and off-band H have been used to investigate the spatial structure of the D3 chromosphere. It was found that spicules provide the major contribution to the intensity of the D3 emission band observed above the limb, with the remainder of the emission coming from a semi-homogeneous background component at low heights.The observations can be understood on the basis of the photoionization model, whereby it is found that helium is only slightly ionized at the height of peak intensity in the D3 emission band, and that spicules are at least 3 times denser than their surroundings at this height.In coronal holes, the D3 emission is confined to isolated emission patches, and these patches contain a fine structure resembling normal chromospheric spicules. 相似文献
4.
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
5.
A compilation of brightness temperature data in the millimetre and sub-millimetre wavelength ranges is used to obtain an empirical relation T
B = C
n between brightness temperature and wavelength, valid between 1 mm and 1 cm. An analytically soluble model, giving electron temperatures and densities between 1500 km and 4000 km above the photosphere is derived from this relationship, and eclipse data of Thomas and Athay, of the emission at the head of the Balmer continuum. Although this over-simplified model lacks precision in the height co-ordinate, it allows a scale height of around 1000 km for electrons to be deduced, and supplies a convincing test for the absence of hydrostatic equilibrium throughout the region. A more comprehensive and reliable though still simplified numerical model is then presented, being a modification of previous models accounting only for millimetre data. It shows marked departure from UV derived models in this region, and an explanation for the discrepancy is proposed in terms of thermal inhomogeneities on the scale of the chromospheric supergranulation. The stratified model is then geometrically modified to account for observed centrelimb profiles of the Sun measured throughout the sub-millimetre and millimetre region. The scale of any roughness thus introduced is related to the notable lack of millimetric limb brightening, and observational tests for that scale are suggested here. A qualitative picture of this part of the chromosphere is proposed, consistent with existing observations in the millimetre, visible and UV regions of the spectrum. 相似文献
6.
Spectroheliograms were obtained in bands centred at 1.2 mm, 0.8 mm and 0.4 mm wavelength during 1969 and 1971. In order to obtain photometrically valid data, a specialized set of reduction techniques was employed, obviating the effects of severe differential attenuation across the disc by atmospheric water vapour and of emission noise from the atmosphere, before taking out the instrumental spread functions of the telescope and detector.Comparison of our maps with those of other observers at 3 mm and 8.6 mm wavelength suggests that the chromospheric brightness temperature increments above active regions show a monotonic increase with increasing height above the photosphere over the normal increase in brightness temperature in the quiet chromosphere. Within the limit of angular resolution of 3 available, no evidence was recorded of normal limb brightening in our three passbands but the presence of isophotes at 50% of the central disc temperature consistently circumscribing the optical limb implies a narrow spike of sub-millimetre brightening close to the limb. 相似文献
7.
Observations of the intensity distribution near the solar limb at 2.43 and 22.5 , show the absence of limb brightening to within 1 or 2 arc sec of the limb. Observations at 1.2 mm indicate limb brightening at this wavelength. These results are compared with the Utrecht Reference Photosphere and with existing data on the solar flux in the millimeter range, and suggest that the temperature minimum is broad and extends above
5000 = 2 × 10–3. A sharp rise of temperature is required above
5000 = 10–5. 相似文献
8.
We describe a new model of the chromosphere based on Lyman-continuum observations by Harvard spectrometers aboard the satellites OSO 4 and OSO 6. The model assumes (a) that a random distribution of optically thick inhomogeneities overlies a plane-parallel homogeneous atmosphere, and (b) that the Lyman continuum in the chromosphere is optically thick and the only significant opacity source between 600 and 912 Å.The temperature, gas pressure, electron pressure, particle densities, and b
1 (the hydrogen ground-state departure coefficient) are calculated as a function of height in the chromosphere.The model reproduces the observed quiet-region intensities in the Lyman continuum. The inhomogeneous structures, which we believe to be spicules, are inferred to be optically thick in the Lyman continuum and to have a source function below that of the mean chromosphere. If they are also optically thick in the free-free (millimeter) continuum and cooler than about 5000K, they could produce the observed limb darkening at 1 and 3 mm. Such low temperatures are at odds with current spicule models, but could exist in the cores of spicules.The Lyman-continuum emission shortward of 750 Å shows an excess emission over that predicted by the above model. This is found to be consistent with the existence of a temperature plateau with T 22000K in the very high chromosphere. 相似文献
9.
New observations of solar spicules at Pulkovo, made simultaneously in 4 spectral regions, are described. The profiles of the H, D3, H, H and K lines were derived for 23 spicules.The spicules occur usually in narrow bundles and can be resolved into separate objects only due to a dispersion of radial velocities inside the bundle. The spicules in D3 are diffuse with faint interspicular emission.The emission of hydrogen, helium and Caii originate in different parts of spicules with different radial and turbulent velocities. The core of a spicule with Caii emission is a narrow rope several tens of km in diameter for the normal section. The optical thickness of a spicule in H is approximately 1.0 and the atomic density varies from 1011 to 1012 cm–3.The helium emission in spicules seems to be produced by different mechanisms, one of them being the external radiation of corona and subcoronal matter.The model of a solar spicule is discussed. 相似文献
10.
H spectra and effectively simultaneous filtergrams were taken at the Fraunhofer Observatory on Capri with the 35 cm domeless Coudé. The spatial resolution of the 19 best spectra selected for analysis was estimated to be 1–2 arc sec. The comparison of several hundred H line profiles emitted by typical chromospheric structure elements with theoretical prediction yielded strong evidence to suggest that the chromosphere consists of two parts: A lower, rather uniform layer at rest superposed by clouds (condensations of great spatial variability) which constitute the well-known structure pattern of H filtergrams. For most image points the line-of-sight velocity, optical thickness, source function and Doppler broadening of these clouds could be determined. While the values of the latter three quantities were found to be similar to what Beckers (1968) has found for limb spicules the velocity of the bright and of the dark mottles is considerably smaller than to be expected if these features were the spicules as seen on the disk. However, our results do not rule out the possibility that the spicules rise at the centers of rosettes where they are difficult to detect.Mitteilung aus dem Fraunhofer Institut No. 105. 相似文献
11.
Mitsuo Kanno 《Solar physics》1983,89(2):253-259
The weakening of the EUV line emission near the Sun's limb is studied to acquire information about the absorbers causing the weakening. The equivalent optical thickness of the absorbers for the Lyman continuum is determined as a function of the distance from the center of the solar disk by use of Skylab spectroheliograms in Oiv λ554 and Ovi λ1032. It is found that (1) the weakening cannot be explained by shielding of EUV emitting sources in terms of completely opaque spicules and (2) the distribution of the equivalent optical thickness on the solar disk is extremely flat with a maximum at a position of ～ 5″ above the white-light limb. The results imply that the absorbers are a number of mass blobs consisting of cool chromospheric material which overlies the EUV emitting sources. It is suggested that both the EUV emitting sources and the absorbers are the remnants of Hα-emitting spicules which are diffused into the corona. 相似文献
12.
Carole Jordan 《Solar physics》1967,2(4):441-450
The relative intensity of two Ci lines at 1993.6 Å and 1657.4 Å, observed in the limb spectrum of the sun, is a factor 2.6 × 103 larger than that expected if both lines were optically thin. It is shown that the observed intensity ratio may be explained in terms of the transfer of photons from 1657.4 Å to 1993.6 Å due to a large optical depth in the line at 1657.4 Å. The observed upper limit on the relative intensity of two further lines at 1992.0 Å and 1657.0 Å has been used to show that the line at 1993.6 Å is optically thin. Hence it is shown that (1657.4 Å) = 1300, and (1993.6 Å) = 0.44. These values provide an independent evaluation of optical depths against which chromospheric models may be checked. Assuming a mean temperature of T
e = 8000 °K, and a mean scale height of 350 km, the optical depths lead to a mean hydrogen-particle density of N (H) = 1.4 × 1012 cm–3. 相似文献
13.
E. Tavabi 《Astrophysics and Space Science》2014,350(2):489-493
A large percent of spicules shows a surge-like behavior on the solar limb, supporting a multi-component model with twisted threads. The counterpart of limb spicules foot-points is investigated on the disk, and this re-examination indicates that the interpretation of transverse motion of off-limb spicules could directly be related to rotational motion at the feet of disk spicules. Related bright elements move and vary in brightness on the timescales of chromospheric oscillations. The motions are similar to random displacements of the bright elements along the network boundaries with amplitudes of about 200 to 400 km, with evidence of “spinning” or vortex motion. We find a clear evidence and in several cases for splitting process and suggesting a formation mechanism for doublet (or multi-component) spicules. A general inter chromospheric network velocity pattern with twists existing before the emergence and eruption of spicules seems to be required. In this paper a helical- kink mode propagation consistent with the new evidence of spicule multiple structure is presented and provides an explanation for the origin of the Alfvenic wave propagation along the spicules. The evidence of spinning spicules remains unclear from disk Dopplergram observations, we use a 3D time slice “column” diagrams (2D in x and y and time in z being the 3d dimension) by consecutive partly transparent slices put in perspective to show the rotational behavior at the chromospheric rosettes, and provide a wealth of information on spinning motion, helical wave propagation and splitting. 相似文献
14.
In this paper, the chromospheric magnetic structures and their relation to the photospheric vector magnetic field in the vicinity of a dark filament in active region 5669 have been demonstrated. Structural variations are shown in chromospheric magnetograms after a solar flare. Filament-like structures in the chromospheric magnetograms occurred after a solar flare. They correspond to the reformation of the chromospheric dark filament, but there is no obvious variation of the photospheric magnetic field. We conclude that (a) some of the obvious changes of the chromospheric magnetic fields occurred after the flare, and (b) a part of these changes is perhaps due to flare brightening in the chromospheric H line.During the reforming process of the dark filament, a part of its chromospheric velocity field shows downward flow, and it later shows upward flow. 相似文献
15.
Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto Expedition at Atar, Mauritania. The integrated intensities of Fexiv
5303, Fex
6374, Fexi
7892, and the continuum are measured as a function of height above the solar limb at eleven points (P.A. = 284–300°) around the third contact point. It is found that a significant amount of the emission in Fex
6374 originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature and the electron density in the interspicular region are derived from the Fex
6374 and the Fexi
7892 intensities on the assumption of spherical symmetry: T
e = 0.9–1.1 × 106 K and N
e = 9–10 × 108 cm–3. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between Fexiv
5303 and the continuum and between Fex
6374 and Fexi
7892 are found. From the Fex
6374 intensities it is inferred that there is a density fluctuation in the innermost corona by at least a factor of two.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 271. 相似文献
16.
K. Nikolskaya 《Solar physics》1978,56(1):71-77
A series of 31 large scale spectra of the spicules near H8-He lines 3889 Å has been photographed at different heights (1500–5000 km) with 53-cm coronagraph. The solar image was 121 mm in diameter, dispersion and spatial resolution were respectively 0.647 Å mm–1 and 1–2. Equivalent widths of both lines have been measured and ratio R = EWHe/EWH8 was obtained. T
e(h) distribution in the averaged spicule deduced differs from that in the recent spicule model by Beckers (1972): the spicules are colder greatly than it was accepted hitherto (T
e 10000 K). The electron temperature in the quiescent prominence which occurred in the spectra was also estimated: T
e 6000 K at h = 4000 and 5000 km. 相似文献
17.
E. M. Reeves 《Solar physics》1976,46(1):53-72
Investigations on the structure and intensity of the chromospheric network from quiet solar regions have been carried out with EUV data obtained from the Harvard spectroheliometer on the Apollo Telescope Mount of Skylab. The distribution of intensities within supergranulation cell interiors follows a near normal function, where the standard deviation exceeds the value expected from the counting rate, which indicates fine-scale structure below the 5 arc sec resolution of the data. The intensities from the centers of supergranulation cells appear to be the same in both quiet regions and coronal holes, although the network is significantly different in the two types of regions. The average halfwidth of the network elements was measured as 10 arc sec, and was independent of the temperature of formation of the observing line for 3.8 < log T
e
< 5.8. The contrast between the network and the centers of cells is greatest for lines with log T
e
5.2, where the network contributes approximately 75% of the intensity of quiet solar regions. The contrast and fractional intensity contributions decrease to higher and lower temperatures characteristic of the corona and chromosphere. 相似文献
18.
Profiles of the K line of Caii are computed for a two component solar chromosphere, chosen to simulate with a simple geometry the chromospheric supergranular network. Each component rises above the BCA photosphere, the boundary component representing the bright network with a sharp temperature rise and the cell component representing the darker region with an extended temperature minimum. Theoretical intensity profiles of the Can K core, calculated as weighted averages over the projected areas of the components, are produced for = 0.6 and 0.3. The line source function and the optical depth are obtained from a self-consistent treatment of the steady state and radiative transfer equations, with complete redistribution assumed for scattering in the line. The atomic model consists of two bound levels and a continuum. It is found that a 4600 K minimum can lead to the successful theoretical prediction of the observed limb darkening and 4300 K radiation temperature of the K1 feature only when very large values of turbulent velocity are assumed to exist in the cell region.Publications of the Goethe Link Observatory, Indiana University, No. 95. 相似文献
19.
Pierre J. Léna 《Solar physics》1968,3(1):28-35
Existing models of the solar atmosphere predict a limb brightening in the far infrared wavelengths. At shorter wavelengths this effect is confined to the extreme limb but at 25 it extends inward from the limb to cos = 0.3. Observations of I()/I(1.0) were made with the McMath Solar Telescope through atmospheric windows at 10.4, 17.9, 20.4, and 24.2 microns, respectively. The measurements, after having been smoothed, are compared with the theoretical predictions taking into account the diffraction pattern of the telescope. The expected brightening does not appear.Kitt Peak National Observatory Contribution No. 260. - Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Presently at Kitt Peak National Observatory, Tucson, Ariz., U.S.A. 相似文献
20.
Harold Zirin 《Solar physics》1969,9(1):77-87
Some parameters of chromospheric structure are drawn from recently published XUV spectroheliograms. The HeII emission above the limb arises from the small amount of He+ still existing at 106°. The larger amounts of He+ in the cooler corona at the poles explain the polar cap absorption in 304. The flat distribution of emission in Oiv and Ov, with a sharp spike at the limb, is caused by the rough structure of the chromosphere and the variable excitation in the emitting spicules. The intensity of the Nevii lines shows that the transition zone between chromosphere and corona is very sharp.This research was supported by the National Aeronautics and Space Administration under Grant NASA NGR 05 002 034. 相似文献