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1.
The formation of the solar Caii K-line core is studied under the assumption of a two component chromosphere for many atmosphere models, which are tested by comparing observed and calculated average intensity profiles at several places on the solar disk. Non-LTE-line profile calculations are made using model atoms of two and three bound levels while the value and depth of the temperature minimum and turbulent velocity gradient are varied. A critique of several broad types of models is provided.Limb darkening of the entire core, a K1 radiation temperature of 4300 K and increasing limbward separation of the K2 peaks are predicted by a combination of a cool component, covering 90% of the solar disk, and a hot component, representing the bright calcium network. The optimum cool component is characterized by a 4200 K temperature minimum and low ( 1 km/sec) microturbulent velocities. The hot component begins its outward temperature rise in the photosphere at 4300 K and is never more than 500 K hotter than the cool component.Publications of the Goethe Link Observatory, Indiana University, No. 116.Presently at New Mexico State University, Las Cruces, New Mexico.  相似文献   

2.
We report high resolution measurements of the center-to-limb variation of the Mgi line at 4571.1 Å. This forbidden line is of interest because it should be formed in LTE. Comparison of our measurements with the Harvard-Smithsonian Reference Atmosphere show that the line center radiation originates in the temperature minimum region from 330 to 550 km above the point where continuum = 1. Observations near the limb confirm that the temperature minimum is 4200K.The National Center for Atmospheric Research and Kitt Peak National Observatory are sponsored by the National Science Foundation.  相似文献   

3.
Line profiles of He ii 4686 Å and He i 4713 Å from active regions in the chromosphere were observed during the total solar eclipse of February 16, 1980, with a grazing incidence objective grating spectrograph. The Doppler width of the He i triplet line of 4713 Å increases with height and the average width is compatible with width of metallic and hydrogen lines, suggesting that the kinetic temperature of He i triplet emitting region is T 8000 K. This can only be explained by recombination after photo-ionization due to coronal UV radiation. The Doppler width of the Paschen line of He ii 4686 is, without any correction for the separation of subcomponents of the line nor non-thermal velocity, 18.4 km s-1. This line width also shows a tendency to increase with height. After comparison with Doppler widths of He i 4713 and the EUV lines, and a necessary subtraction of non-thermal velocity, it is shown that this line is emitted in a 2 × 104 K temperature region, which again supports the view that this line is emitted through the recombination process after photoionization due to coronal XUV radiation below 228 Å.  相似文献   

4.
Spectra of several strong lines of sunspots have been obtained with the Echelle spectrograph at the Vacuum Tower Telescope, Sacramento Peak Observatory. With a variety of model atmospheres, Ca ii H, K, and 18498 line profiles were calculated using a non-LTE line formation procedure.In the present study we examined only a specific part of the sunspot umbra which is thought to be coolest over the spot. An optimum model representing such a region is presented and its physical properties are discussed.This work has been supported by the U.S. - Republic of Korea Cooperative Science Program (K-24).  相似文献   

5.
We have used the SPO tower telescope and echelle spectrograph to study differences in the profiles of three Fei lines, between magnetic network and cells. Ca K slit-jaw pictures were used to identify the network and cell areas, and mean network and cell profiles were computed from digitized spectra for the g = 0 lines 4065, 5434, and the g = 1.5 line 5233. The profile bisectors show that the wings of all three lines are red-shifted in the network by between 75–200 m s–1 relative to the cell profiles. But the redshift decreases in the line core and becomes less than the standard error of 20 m s–1 near the line core minimum. This disappearance of the redshift at the cores of all 3 lines formed over the height range 250–500 km above 0.5 = 1, argues against a steady downflow at supergranule boundaries. We show that such red-shifted wings and a relatively unshifted core can result if granular convection is suppressed near the network flux tubes, without implying any downflow in the vicinity of these flux tubes. Our results also indicate that searches for large-scale convective velocity patterns should measure shifts of the line core, rather than the line wings which appear to be very sensitive to inhomogeneities in granule structure.Visiting Astronomers, Sacramento Peak Observatory.  相似文献   

6.
Ion emission line intensities between 1170 and 1700 Å allow one to determine the differential emission measure (DEM) and electron pressure of the plasma in the solar transition region (TR). These line intensities together with their Doppler shifts and line widths are measured simultaneously for the first time above a sunsport from data obtained with the NRL High Resolution Telescope and Spectrograph with 0.06 Å spectral and 1 spatial resolution.The Doppler shifts show both subsonic and supersonic flow in the same line of sight over the umbra. The temperature structure for 40 resolution elements in the sunspot umbra and penumbra is derived from the DEM and the observed electron pressures.Extrapolation of the emission measure curves supports the previous EUV and X-ray observations that coronal plasma above sunspots with T e>106 K is reduced while emission from TR plasma between 2×105 and 106 K is greatly enhanced relative to quiet or active regions. This enhancement shifts the minimum of the DEM to lower temperatures and increases the slope at 2×105 K by a factor of two.New pressure diagnostics using the emission line intensity ratios of C iv to N iv are presented, and applied to the data.The energy balance in the TR for the sunspot umbra is dominated by radiative losses from the large amount of TR plasma.An estimate of the energy budget shows that an energy input is required to balance the radiative energy losses above the umbra. The observed divergence of the enthalpy flux for the umbral downflows can balance these radiative losses for T e between 30000 and 200 000 K.A typical umbral model of T e versus reduced mass column density is compared with one for chromospheric temperatures determined from the Ca H and K lines.Institute of Theoretical Astrophysics, University of Oslo, Norway.  相似文献   

7.
We have calculated the emission spectra of hydrogen and sodium atoms in the cool part of prominence models which satisfy simultaneously the constraints of radiative transfer, statistical equilibrium and charge-particle conservations.In the considered range of our model parameters, emission strengths of H and Nai D lines increase with the temperature and the total number density. Low-pressure models raise the ionization rate highly but yield very weak Nai D line intensities, since these model prominences contain small amounts of free electrons and sodium atoms which have a deep relation with the formation of sodium lines. We find that sodium D lines should be emitted in the high pressure region of prominences, and that their intensities are difficult to attain in the cool core of any model prominence with a temperature as low as 4000 K. In order to explain consistently the spectral emissions of H and Nai D lines observed in quiescent prominences, a total number density higher than 4 x 1011 cm-3 and a temperature over 5000 K are required at least in the cool part of prominences.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 282.  相似文献   

8.
The spatial and temporal evolution of the high temperature plasma in the flare of 1973 June 15 has been studied using the flare images photographed by the NRL XUV spectroheliograph on Skylab.The overall event involves the successive activations of a number of different loops and arches bridging the magnetic neutral line. The spatial shifts and brightenings observed in the Fe xxiii–xxiv lines are interpreted as the activation of new structures. These continued for four or five minutes after the end of the microwave burst phase, implying additional energy-release unrelated to the nonthermal phase of the flare. A shear component observed in the coronal magnetic field may be a factor in the storage and release of the flare energy.The observed Fe xxiii–xxiv intensities define a post-burst heating phase during which the temperature remained approximately constant at 13 × 106 K while the Fe xxiv intensity and 0–3 Å flux rose to peak values. This phase coincided with the activation of the densest structure (N e = 2 × 1011 cm–3). Heating of higher loops continued into the decay phase, even as the overall temperature and flux declined with the fading of the lower Fe xxiv arches.The observed morphology of individual flaring arches is consistent with the idea of energy release at altitude in the arch (coincident with a bright, energetic core in the Fe xxiv image) and energy flow downward into the ribbons. The Doppler velocity of the Fe xxi 1354 Å line is less than 5 km s–1, indicating that the hot plasma region is stationary.The relation of this flare to the larger class of flares associated with filament eruptions and emerging magnetic flux is discussed.  相似文献   

9.
Calculations of electron temperature (T e) and density (N e) sensitive line ratios in Sixi involving transitions in the 358–604 wavelength range are presented. These are shown in the form of ratio-ratio diagrams, which should in principle allow bothN e andT e to be deduced for the Sixi line-emitting region of a plasma. However a comparison of these with observational data for two solar flares, obtained with the Naval Research Laboratory's S082A spectrograph on boardSkylab, reveals that the experimental ratios are much larger than expected from theory, which is probably due to the Sixi lines in the S082A spectra being blended with transitions from species including Nev, Fexi, and Fexii. Possible future applications of the Sixi results to spectral data from the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory are briefly discussed.  相似文献   

10.
A technique developed for analysing line profiles with both speed and high accuracy was used to study the physical conditions of a coronal formation near a quiescent prominence. Detailed analyses of five coronal lines (Fe xiv λ 5303, Fe x λ 6374, Ni xv λ 6702, Fe xv λ 7059, and Fe xi λ 7892) provided total intensities, Doppler width temperatures, ionization temperatures, and velocities. Dissimilar spatial fluctuations in intensity are obvious for ions grouped according to (low vs high) ionization potentials. The intensity of the green line shows a local minimum around the observed quiescent prominence; a corresponding but much more diffuse pattern is visible in the red line intensity. Large differences are observed in temperatures derived by different means. In particular, , while , and . The differences between and are taken as direct evidence of temperature inhomogeneity. One can thus put little significance in T e (xi/x). T D(λ5303) and T e (xv/xiv) fluctuate nearly in parallel at each slit height, with a weak local minimum evident around the prominence. The discrepancy between these two can be removed if a non-thermal turbulent motion of 6–16 km s−1 is assumed. Variations with height of both T D(λ5303) and T e (xv/xiv) suggest that the coronal temperature maximum is located no more than 15000 km above the top of spicules. A negative gradient of about 6 deg km−1 is found in the height variation of T D(λ5303). The height variation of the green line wavelength shows that the majority of coronal material in this region is flowing from west to east on the Sun, with the highest velocity of 12 km s−1 found at the lowest heights. This motion is in the same sense as that of the nearby coronal rain, as determined both from the spectra and wavelength-shifted Hα filtergrams. Superposed on the above flow is a systematic velocity field of up to ±5 km s−1. This field similarly reaches maximum amplitudes at lowest heights showing a local maximum around the prominence. On leave from Institute of Earth Science and Astrophysics, Shiga University, Ohtsu 520, Japan, as 1973–75 National Academy of Science/National Research Council Senior Post-Doctoral Research Associate at Sacramento Peak Observatory.  相似文献   

11.
The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum Tower Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe active region AR 2490 on two consecutive days at soft X-ray, ultraviolet, optical and radio wavelengths (2, 6, and 20 cm), with comparable angular resolution (2 to 15) and field of view (4 × 4). The radio emissions at = 6 cm and 20 cm show a double structure in which one component is associated with bright H plage, C iv and soft X-ray emission, and the other component is associated only with sunspots. No radiation at = 2 cm is detected in this latter component. Coronal temperature and emission measure derived from X-ray lines indicate that the dominant radiation mechanism of the plage-associated component is due to thermal bremsstrahlung while the gyroresonance absorption coefficient must be invoked to account for the high brightness temperature (T b 2×106K) observed in the sunspot associated component. The high magnetic field strength needed (600 G at a level where T2×106K) is explained assuming a thin transition zone, in order to reach a high electron temperature close to the sunspot, where the magnetic fields are stronger. A higher temperature gradient above sunspots is also consistent with the absence of detectable C iv emission.Cooperative study of the SMY-FBS Project.On leave from the University of Napoli.On leave from the University of Torino.On sabbatical leave 1980–81 at the Arcetri Observatory.On leave from Toyokawa Observatory, Japan.  相似文献   

12.
In this paper we study the far-UV as well as the UV spectrum of the spectroscopic binary system SZ Psc in the wavelength ranges 1235–1950 Å and 2710–3090 Å, respectively, from spectra obtained with the International Ultraviolet Explorer (IUE). The UV spectrum of SZ Psc is mainly an emission spectrum. The short wavelength region includes emission lines formed from the low chromosphere to the transition region (e.g., Siiv,Civ, andNv) and also a deep and broad absorption line of Feii.The Mgii[1] resonance doublet at about 2800 Å presents a P Cygni profile and a multiple structure with two emission and two absorption satellite components. We also present the emission measure diagram in the temperature region 4.4T e <53.  相似文献   

13.
Extreme ultraviolet spectra of several active regions are presented and analyzed. Spectral intensities of 3 active regions observed with the NRL Skylab XUV spectroheliograph (170–630 Å) are derived. From this data density sensitive line ratios of Mg viii, Si x, S xii, Fe ix, Fe x, Fe xi, Fe xii, Fe xiii, Fe xiv, and Fe xv are examined and typically yield, to within a factor of 2, electron pressures of 1 dyne cm–2 (n e T = 6 × 1015 cm–3 K). The differential emission measure of the brightest 35 × 35 portion of an active region is obtained between 1.4 × 104 K and 5 × 106 K from HCO OSO-VI XUV (280–1370 Å) spectra published by Dupree et al. (1973). Stigmatic EUV spectra (1170–1710 Å) obtained by the NRL High Resolution Telescope and Spectrograph (HRTS) are also presented. Doppler velocities as a function of position along the slit are derived in an active region plage and sunspot. The velocities are based on an absolute wavelength scale derived from neutral chromospheric lines and are accurate to ±2 km s–1. Downflows at 105 K are found throughout the plage with typical velocities of 10 km s–1. In the sunspot, downflows are typically 5 to 20 km s–1 over the umbra and zero over the penumbra. In addition localized 90 and 150 km s–1 downflows are found in the umbra in the same 1 × 1 resolution elements which contain the lower velocity downflows. Spectral intensities and velocities in a typical plage 1 resolution element are derived. The velocities are greatest ( 10 km s–1) at 105 K with lower velocities at higher and lower temperatures. The differential emission measure between 1.3 × 104 K and 2 × 106 K is derived and is found to be comparable to that derived from the OSO-VI data. An electron pressure of 1.4 dynes cm–2 (n e T = 1.0 × 1016 cm–3 K) is determined from pressure sensitive line ratios of Si iii, O iv, and N iv. From the data presented it is shown that convection plays a major role in determining the structure and dynamics of the active region transition zone and corona.  相似文献   

14.
O vi ( = 1032 Å) profiles have been measured in and above a filament at the limb, previously analyzed in H i, Mg ii, Ca ii resonance lines (Vial et al., 1979). They are compared to profiles measured at the quiet Sun center and at the quiet Sun limb.Absolute intensities are found to be about 1.55 times larger than above the quiet limb at the same height (3); at the top of the prominence (15 above the limb) one finds a maximum blue shift and a minimum line width. The inferred non-thermal velocity (29 km s–1) is about the same as in cooler lines while the approaching line-of-sight velocity (8 km s–1) is lower than in Ca ii lines.The O vi profile recorded 30 above the limb outside the filament is wider (FWHM = 0.33 Å). It can be interpreted as a coronal emission of O vi ions with a temperature of about 106 K, and a non-thermal velocity (NTV) of 49 km s–1. This NTV is twice the NTV of quiet Sun center O vi profiles. Lower NTV require higher temperatures and densities (as suggested by K-coronameter measurements). Computed emission measures for this high temperature regime agree with determinations from disk intensities of euv lines.  相似文献   

15.
We report some results of a rocket experiment flown on 29 April, 1971. A survey of the solar corona was carried out with a pair of collimated Bragg spectrometers to study the resonance, intersystem and forbidden line emission from the helium-like ions O vii (22 Å) and Ne ix (13 Å). In the direction of dispersion the collimator provided a field of view of 1.7. Also, the continuum radiation near 3 Å was monitored by a collimated proportional counter within a view angle of 4.2. The observed X-ray emission came from the general corona, seven plage regions, and one dynamic feature- the late stage of a small flare. From the intensity of the O vii and Ne ix resonance lines the electron temperature and emission measure of the individual emitting regions are derived on the basis of two models, one (a) in which the region is assumed to be isothermal and another (b) in which the emission measure decreases exponentially with increasing temperature. The latter model, which is the most adequate of the two, yields for the electron temperature of the time-varying feature 2–3 × 106 K, for the other active regions 1.5–2.5 × 106 K, and for the general corona 1.3–1.7 × 106 K. The Ne ix emitting regions are about 1.5 times as hot as the O vii regions. The emission measure ranges from 0.4–2.3 × 1048 cm–3 for all active regions and is about 2 × 1049 cm–3 for one hemisphere of the general corona above 106 K. From an analysis of the ratio, R, of the forbidden and intersystem lines of O vii we conclude that none of the regions producing these lines at the time of the rocket flight had electron densities exceeding about 3 × 109 cm–3. Our data demonstrate a dependence of R upon temperature in agreement with the theory of Blumenthal et al. (1971). The wavelengths for the intersystem, the 1s 22s 2 S e–1s2p2s 2 P 0 satellite, and the forbidden transition show in the case of Ne ix improved agreement with predictions. The observed strength of the satellite lines for both O vii and Ne ix agrees with the predictions of Gabriel's (1972) theory, which attributes their formation to dielectronic recombination.We are saddened to report the death of A. J. Meyerott on 13 November, 1971.  相似文献   

16.
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   

17.
An analysis of the spectral distribution of intensity of the Hei recombination continuum is probably the only direct method for determination of the electron temperature of helium emission regions on the Sun. On the basis of data on the Hei Lyman continuum, obtained by Dupree and Reeves from OSO-4, the electron temperature of undisturbed helium regions is determined: T e = = 12500 K. Such a low T e value is a serious argument in favour of the predominant role of UV coronal radiation in the helium ionization on the Sun. Comparison of the Hei Lyman continuum data with results of observations of the 10830 line showed that the visible helium lines and Hei Lyman continuum are produced within the same regions of the undisturbed solar atmosphere at T e = 12500 K.  相似文献   

18.
R. Fisher  T. Pope 《Solar physics》1971,20(2):389-399
Nine coronal emission lines representing five stages of Fe ionization and one stage of Ni were observed in an enhanced coronal region. The data from these observations are presented along with a density model of the enhanced region obtained from the FeXIII and NiXV emission line ratios as a function of position angle. The electron densities obtained from FeXIII lines range from N e = 108 to 109 cm–3, and are slightly lower for NiXV line data. Estimates of the variation of temperature over the enhanced region are inferred from the observed line intensities.  相似文献   

19.
Radio measurements of the electron temperature ofHii regions are obtained from the ratio of the brightness temperature of a hydrogen recombination line to that of the adjacent continuum, while optical measurements are obtained from the ratio of [Oiii] forbidden-line intensities. The radio and optical measurements made under the assumption of an isothermalHii region,T R andT opt respectively, are combined to derive a temperature distribution for an entire nebula. A sphericalHii region in local thermodynamic equilibrium with constant density which is optically thin in both the line and the continuum is used as a model. Assuming linear temperature gradients withT R=6000K andT opt=10000K, it is found thatT=12000K (1–0.74r/R), wherer is the distance from the center andR is the radius of the nebula.  相似文献   

20.
We have qualitatively analyzed, in the H and K lines spectral region, 31 flares covering part of umbrae or penumbrae of sunspots. A strong narrowing of the emission lines has been observed over the umbrae, and the lines are, in general, much weaker than in common flares suggesting that the optical thickness is quite low in these parts. We have calculated the Stark broadening of the H line from the general theory, and it has been applied to obtain the electron density in 9 flare spectra. In all cases it has been found that n e > 1013 cm–3. Goldberg's method has been applied to find the kinetic temperature from the H and K lines of Ca ii, and from the ratio between the central intensities of the lines we have calculated the optical thickness in the K line. Much evidence supports the assumption that the flare emission is highly diluted in the cases considered, and we propose a two-component model for the calcium emission lines.
  相似文献   

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