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1.
We study the center-limb (CL) variation of the average profiles of four Ca i lines near 6500 and compare these observations with synthetic data obtained from several line formation models having different thermal structures, line parameters, LTE and non-LTE conditions, and micro and macroturbulence values, to assess the formation characteristics of our Ca i lines in the solar photosphere.Comparison of numerical results with observations indicates that non-LTE is indispensable to fit the CL variation of the central residual intensity for the line 6493, and anisotropic microturbulence is indispensable to improve the CL behavior of the equivalent widths for all lines. The Ca i line analysis favors a cool photospheric model, but this cannot be disentangled clearly from the effects of non-LTE and small-scale velocity fields on the grounds of the present line formation models. 相似文献
2.
Broad band pinhole photometer intensity observations of 15 large sunspots covering the spectral region 0.387–2.35 m are presented. The data are based on measurements on approximately 500 days during the period June, 1967 to December, 1979.We have found real and significant intensity differences between large sunspots. These differences may be explained by a systematic variation in the umbral temperature throughout the solar cycle. A connection between umbra intensity and heliographic latitude is discussed.No center-limb variation in the umbra/photosphere intensity ratio is detected. We have searched for possible connections between umbra intensity and a number of other sunspot parameters, like the spot size, without detecting any significant correlation. We conclude that the umbra/photosphere intensity ratio seems to be a unique function of epoch for large sunspots. 相似文献
3.
Lawrence W. Ramsey 《Solar physics》1977,51(2):307-313
A systematic study of the internal horizontal (line-of-sight) motions of quiescent prominences which were observed at the limb has been made by using fourier techniques to analyse the shift of the Ca ii K line as a function of height above the limb. The results indicate that a characteristic size for the velocity elements is present in 70% of the 13 prominences studied. This size of 4700 km is attributed to Alfvén waves induced by horizontal convective motions in the photosphere as previously suggested by Malville. The qualitative aspects of the observations are described by a simple model which is based on this hypothesis.Presently at Department of Astronomy, Pennsylvania State University, 525 Davey Lab., University Park, PA 16802.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
4.
Temperature and velocity structures above granules and intergranular lanes were studied on spectrograms covering Caii H and K lines. In agreement with our earlier results, it was confirmed more quantitatively that there appear two kinds of bright continua, one in the outer wings (granular continuum) and the other in the inner wings (temporarily called K0-continuum) of Caii H and K lines, and that these two kinds of bright continua are located more or less in a complementary fashion. Further, it was found that the bright K0-continuum is well associated with higher central residual intensity of absorption lines. These facts suggest that in the upper photosphere of, say, < 0.1, there are high temperature regions in the intergranular lanes. Motions above granular regions are essentially upwards, whereas those of intergranular regions are predominantly downwards, and in the uppermost photosphere the motions become more random. 相似文献
5.
A solar flare with both H and Fe i 5324 emissions was observed in AR 7529 (S13, E65) on 24 June, 1993 at the Bejing Astronomical Observatory. Our calculations show that the Fe i 5324 emission region of the flare was located in the low photosphere at a height of about 180 km above 5000 = 1, which is lower than many previous studies of white-light flares. To study a Fe i 5324 flare, which represents a kind of extreme case in solar flares, would be useful for clarifying some arguments in the researches of white-light flares as well as for understanding the mechanism of solar flares.The synthetic analyses from vairous features of the flare lead to the following possible exciting mechanism of the Fe i 5324 flare: owing to the flow of energetic electrons from the corona and probably also the thermal conduction downward into the lower atmosphere, a condensation with a temperature higher than that below it was formed near the transition region. Then the low photosphere was heated through backwarming. The Fe i 5324 flare occurred as an indicator of the excitation in the low photosphere. 相似文献
6.
Direct measurements of plasma motions in the photosphere are limited to the line-of-sight component of the velocity. Several algorithms have therefore been developed to reconstruct the transverse components from observed continuum images or magnetograms. We compare the space and time averages of horizontal velocity fields in the photosphere inferred from pairs of consecutive intensitygrams by the LCT, FLCT, and CST methods and the DeepVel neural network in order to identify the method that is best suited for generating synthetic observations to be used for data assimilation. The Stein and Nordlund (Astrophys. J. Lett.753, L13, 2012) magnetoconvection simulation is used to generate synthetic SDO/HMI intensitygrams and reference flows to train DeepVel. Inferred velocity fields show that DeepVel performs best at subgranular and granular scales and is second only to FLCT at mesogranular and supergranular scales. 相似文献
7.
A velocity field is found to occur prior to the birth of sunspots or during the rapidly developing phase of new spots. Fraunhofer lines are always shifted redwards in the observed active regions which are situated at various distances from the disk center. The velocity amplitude derived from Na i D1-line, 5895.940, amounts to, at maximum, 1.5 km s–1 which is always a little larger than that derived from the weaker line, NI i 5892.883. The velocity field disappears when the spot ceases to grow. The lifetime of the velocity is, at least, 1 hr. The velocity field is interpreted in terms of the continuous downward flow in the process of formation of sunspots.Bray and Loughhead (1964) regard the disturbance in the granulation pattern accompanying the birth and growth of sunspot pores as an evidence of the existence of rising loops of magnetic flux. In view of the similarity of the phase of development of active regions and the lifetime in the observations by Bray and Loughhead and by us, we suggest that the velocity field may be a spectroscopic feature accompanying the rising magnetic loops in the photosphere and the chromosphere. We briefly discuss the observed mode of penetration of the magnetic flux to the solar surface before and after the appearance of AFS's. 相似文献
8.
J. C. Del Toro Iniesta M. Collados J. Sánchez Almeida V. Martínez Pillet B. Ruiz Cobo 《Astrophysics and Space Science》1990,170(1-2):9-16
We present spectroscopic observations, with high spatial resolution, of Caii K bright points very near the disc centre. Magnetic concentrations have been detected in these network (facular) points by only using intensity profiles of the well-known pair of lines Fei5250.22 Å and 5247.06 Å. No brightening of these structures with respect to the quiet photosphere can be ascertained within an accuracy threshold of 1.2%.Based on observations made with the Vacuum Gregory Telescope (V.G.T.) operated on the island of tenerife by the Universitäts-Sternwarte (Göttingen) in the Spanish Observatorio del Teide of the Instituto de Astrofisica de Canarias.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
9.
Brigitte Schmieder 《Solar physics》1976,47(2):435-460
Using a 32 minutes sequence of observation, brightness and velocity fluctuations in the wings of the Mgi line at 5172.7 Å and Fe ii line at 5197.578 Å are analysed. The analysis of phase shifts and amplitude ratios leads to the following conclusions:
| (1) |
In the frequency range from (400s)–1 to (130s)–1, we find the existence of three modes of waves: internal gravity, evanescent and propagating acoustic waves which appear with increasing frequency. A satisfactory agreement for velocity between observations and theory in the range of horizontal wavelengths \s>5000km with a theoretically local relaxation time
–180s-40s is obtained.
The calculation of intensity fluctuations shows that the Mgi line is sensitive to temperature and density fluctuations while the Fe ii line is only sensitive to temperature perturbation. For the best fit with the same value of
–1 to both lines (i.e., Fe ii and Mg i) it is found necessary that the density effect should be taken into account for the Mg i intensity fluctuations. The relaxation time deduced from observed intensity fluctuations seems to decrease with the period of oscillation. This suggests the presence of a dissipation process. 相似文献
10.
A time sequence of magnetograms and velocity-grams in the H and Fe i 6569 Å lines has been made at a rate of 12 h–1 of McMath Region 10385 from 26 to 29 October, 1969. The 14 flares observed during this period have been studied in relation to the configuration and changes in the magnetic and velocity fields. There was little correlation between flare position and the evolutionary changes in the photospheric magnetic and velocity field, except at large central meridian distances where the velocity observations suggested shearing taking place at flare locations. At central meridian distances > 30° we found that flares are located in areas of low line-of-sight photospheric velocity surrounded by higher velocity hills. The one exception to this was the only flare which produced a surge. Blue-shifted velocity changes in the photosphere of 0.3 to 1 km s–1 were observed in localized areas at the times of 8 of 14 flares studied.Visiting Astronomer, Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
11.
Eric G. Chipman 《Solar physics》1977,55(2):277-285
Satellite observations of velocity and intensity oscillations were made of the upper chromospheric line C ii 1336. The dominant period of oscillation is 300 s, with little evidence of the power peak in the range 150–200 s which has been observed in other chromospheric lines. Peak-to-peak amplitudes are 2 km s–1 and 8% in velocity and intensity, respectively. Tentative evidence for 900-s periodicity is presented. Relative phase measurements show that maximum intensity for the 300-s oscillation leads maximum blueshift by approximately 145 s. Comparison of line and background (scattered light) intensity variation shows upward wave propagation, with time delays between the 1800 continuum and C ii 1336 variation of 27 s and 70 s for different cases. 相似文献
12.
B. Schmieder 《Solar physics》1978,57(2):245-253
In a previous paper (Schmieder, 1977), we solved simultaneously the hydrodynamical and radiative transfer equations, so we do not have to assume any relaxation time of the atmosphere. In this paper, we use that theory to interpret photospheric observations of the Mg i line at 5172 Å.For periods between 400 and 140 s, the phase-shifts observed between velocities and the phase shifts between intensity and velocity fluctuations are explained by the existence of radiative dissipation coupled with evanescent waves or upward propagating waves, according to the frequency.For smaller periods partial or total reflections must be considered.The results relative to radiative dissipation are expressed in terms of the variation of a relaxation time with frequency through the atmosphere (10–3<5000<1). 相似文献
13.
We compare the line profiles and frequencies of low =0, 1, 2 acoustic oscillations seen in observations in velocity (by the GOLF and GONG experiments) and in intensity (LOI instrument). Our study indicates that the systematic shift between the frequencies of low- pmodes in intensity and in velocity measurements recently discovered by Toutain and co-workers is merely an artifact of their reduction techniques. The results obtained agree perfectly with the theoretical expectation that solar oscillations are the global eigenmodes simultaneously visible in velocity and intensity with the frequencies and line profiles coinciding within the error bars. 相似文献
14.
Richard C. Altrock 《Solar physics》1969,7(3):343-350
Spectroheliograms have been obtained in the line cores of two infrared multiplets of neutral oxygen. Those made in the lines of the 7770 Å multiplet show a very smooth intensity distribution, with faculae and sunspot penumbrae at a very low contrast with respect to the undisturbed photosphere. Spectroheliograms made in the core of 8446.37 Å show evidence of coupling with chromospheric features and of blending with a line of neutral iron.An analysis of a 7772 Å spectroheliogram indicates that a magnetic field of approximately 1500 G is required to produce the disappearing penumbra phenomenon. This value is consistent with the recent observations of Beckers and Schröter (1969). 相似文献
15.
A. A. Van Ballegooijen 《Solar physics》1984,91(2):195-217
From a high-resolution spectrum of a sunspot umbra (1.1 < < 2.3 m) we derive models of the temperature stratification in the deep layers of the umbra. The observed spectrum is corrected for straylight using the Hi Paschen line at gl = 1.282 m. A method is described for the iterative fitting of empirical temperature models to spectral information, and the method is applied to the present data. We find that the observed profiles of 3 high-excitation lines of Sii and the observed continuum contrast between umbra and photosphere cannot be reproduced with a single one-component model of the umbral atmosphere: the Si i lines require a model that is 460 K hotter at gt
0.5 = 3 than the continuum model. This indicates that hot and cool components coexist within the umbra. A temperature model derived from the relative intensity in the wings of 3 low-excitation lines of Mgi, Ali, and Sii is not significantly different from the continuum model.Based on observations obtained at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under contract with the National Science Foundation. 相似文献
16.
Several lines of neutral oxygen observed at various positions on the solar disk were used to study the influence of (1) the temperature distribution, (2) the velocity field, and (3) the damping on the line profiles and the abundance of oxygen in the photosphere. Theoretical profiles were calculated on the basis of four different model atmospheres in LTE. It was found that the model proposed by Holweger (1967) best reproduced the center-to-limb observations of the lines studied. The weighted mean of the oxygen abundance turned out to be log
O = 8.83 on the basis of log
H = 12.00. 相似文献
17.
New observations of the umbral limb-darkening are presented. We find a real and significant decrease in the umbra/photosphere intensity ratio towards the limb. This result contrasts the findings of previous authors and we believe this to be the first time such a decrease is reported. Our conclusion is based on broad band pinhole photometer intensity observations of 22 large sunspots covering the spectral region 0.387–2.35 m. The data are selected from measurements on approximately 600 days during the last 15.5 yr. The application of the limb-darkening data to the study of the temperature stratification in the umbra is briefly discussed. The observations confirm the suggestion that the umbra/photosphere intensity ratio seems to be a linear function of the phase in the solar cycle. 相似文献
18.
We have examined whether the motion field in the photosphere in the range of optical depths 0.25< 0< 0.6 is dominated by thermal convection or by vibrations. The observed asymmetries of infrared Fraunhofer lines indicate the presence of motions, and the fact that the asymmetry is zero for lines of low excitation and increases with the excitation potential shows that these motions are chiefly convective in this part of the photosphere: upward moving elements appear to be hotter than downward moving ones.Assuming furthermore that the photosphere can be described by a three-column model, with temperature differences as given by Edmonds (1967), we find that in the range of optical depths given above, where T seems to vary between 80 and 160 °K, average convective velocities of 2.3 to 3.2 km/sec should occur. This result is in numerical agreement with (a) a previous one by the present authors (1967) derived from the variation of line asymmetry with depth in lines of one multiplet, (b) a finding by Lambert and Mallia (1968) deduced from absolute wavelength measurements of Fraunhofer lines, and (c) a recent result of Beckers (1968) found from a comparison of two granulation pictures obtained simultaneously with a narrow-band filter centred on the two wings of a faint line. 相似文献
19.
N. N. Kondrashova 《Kinematics and Physics of Celestial Bodies》2016,32(2):70-77
Semiempirical models of the photosphere of an Ellerman bomb in the NOAA 11024 active region were obtained using profiles of Stokes parameters I, Q, U, and V of photospheric lines. Spectropolarimetric observations were conducted using the French–Italian THEMIS telescope (Tenerife, Spain). The SIR inversion code [28] was used in the modeling. The models have two components: a magnetic flux tube and nonmagnetic surroundings. The dependences of temperature, magnetic field strength, inclination of the magnetic field vector, and line-of-sight velocity in the tube on the optical depth were obtained. The models demonstrate that the thermodynamic parameters of the Ellerman bomb photosphere differ considerably from those of the quiet photosphere. The temperature in the tube model varied nonmonotonically with height and deviated by up to 700–900 K from its values for the quiet photosphere. Downflows were observed in the lower and the upper photospheric layers. The line-of-sight velocity in the upper layers of the photosphere was as high as 17 km/s. The magnetic field strength in the models varied from 0.1–0.13 T in the lower photospheric layers to 0.04–0.07 T in the upper ones. The physical state of the photosphere did change in the course of observations. 相似文献
20.
R. Kariyappa 《Solar physics》1996,165(2):211-222
We have analysed a 35-min-long time sequence of spectra in the Caii H line, Nai D1 and D2 lines, and in a large number of strong and weak Fei lines taken over a quiet region at the center of the solar disk. The time series of these spectra have been observed simultaneously in these lines under high spatial, spectral, and temporal resolution at the Vacuum Tower Telescope (VTT) of the Sacramento Peak Observatory. We have derived the line profiles and their central intensity values at the sites of the chromospheric bright points, which are visible in the H line for easy identification. We have done a power spectrum analysis for all the lines, using their central intensity values to determine the period of oscillations. It is shown that the 3 Fei lines, present 23 Å away from the core of the H line representing the pure photospheric lines, Nai D1 and D2 lines, 6 Fei lines at the wings of H line, and Can H line exhibit 5-min, 4.05-min, 3.96-min, and 3.2-min periodicity in their intensity oscillations, respectively. Since all these lines form at different heights in the solar atmosphere from low photosphere to middle chromosphere and show different periodicities in their intensity oscillations, these studies may give an idea about the spatial and temporal relation between the photospheric and chromospheric intensities. Therefore these studies will help to better understand the physical mechanisms of solar oscillations. It is clearly seen that the period of intensity oscillations decreases outward from the low photosphere to the middle chromosphere. Since we have studied a single feature at a time on the Sun (i.e., bright points seen in the H line) in all these spectral lines simultaneously, this may explain about the footpoints of the bright points, the origin of 3-min oscillations, and the relation to other oscillations pertaining to these locations on the Sun. We have concluded that 80% of the bright points are associated with dark elements in the true continuum, and they may seem to have a relationship with the dark intergranular lanes of the photosphere, after carefully examining the brightness (bright threads) extending from the core to the far wings of the H line at the locations of a large number of bright points, using their time sequence of spectra.NRC Resident Research Associate, on leave from Indian Institute of Astrophysics, Bangalore 560034, India. 相似文献
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