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1.
High spatial resolution spectral observations of five hedgerow prominences were made in H, He i D3 and Ca ii H and K.The observed relations between the lines were not the same in all prominences. The Ca ii H and K lines were 2–4 times brighter relative to H and D3 than predicted theoretically. The optical thickness of H was less than for the H and K lines, the H was optically thin in medium faint prominence structures. Faint structures appeared slightly hotter than bright structures.On leave from Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, Oslo 3, Norway.  相似文献   

2.
The present paper is devoted to the interpretation of linear polarization data obtained in 14 quiescent prominences with the Pic-du-Midi coronagraph-polarimeter by J. L. Leroy, in the two lines Hei D3 andH quasi-simultaneously. The linear polarization of the lines is due to scattering of the anisotropic photospheric radiation, modified by the Hanle effect due to the local magnetic field. The interpretation of the polarization data in the two lines is able to provide the 3 components of the magnetic field vector, and one extra parameter, namely the electron density, because the linear polarization of H is also sensitive to the depolarizing effect of collisions with the electrons and protons of the medium. Moreover, by using two lines with different optical thicknesses, namely Hei D3, which is optically thin, and H, which is optically thick ( = 1), it is possible to solve the fundamental ambiguity, each line providing two field vector solutions that are symmetrical in direction with respect to the line of sight in the case of the optically thin line, and which have a different symmetry in the case of the optically thick line.It is then possible to determine without ambiguity the polarity of the prominence magnetic field with respect to that of the photospheric field: 12 prominences are found to be Inverse polarity prominences, whereas 2 prominences are found to be Normal polarity prominences. It must be noticed that in 12 of the 14 cases, the line-of-sight component of the magnetic field vector has a Normal polarity (to the extent that the notion of polarity of a vector component is meaningful; no polarity can be derived in the 2 remaining cases); this may explain the controversy between the results obtained with methods based on the Hanle effect with results obtained through the Zeeman effect. A dip of the magnetic field lines across the prominence has been assumed, to which the optically thick H line is sensitive, and the optically thin Hei D3 line is insensitive.For the Inverse prominences, the average field strength is 7.5±1.2 G, the average angle,, between the field vector and the prominence long axis is 36° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 29° ± 20°, and the average electron density is 2.1 × 1010 ± 0.7 × 1010 cm–3. For the Normal prominences, the average field strength is 13.2±2.0 G, the average angle,, between the field vector and the prominence long axis is 53° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 0° ± 20° (horizontal field), and the average electron density is 8.7 × 109 ± 3.0 × 109 cm–3.  相似文献   

3.
The Na i D emission lines are found to brighten temporarily in restricted regions of quiescent prominences and we call the phenomena the Na i D brightenings. The comparison of observed intensities of Na i D lines with model calculations shows that the phenomena is attributed to a kind of local activation of quiescent prominences accompanied by mass motions. The Na i D lines are emitted from extraordinarily high pressure regions in which the pressure rises up to 0.37 2.7 dyn cm–2 and the temperature seems to be in the range between 5800 7000 K. The line-of-sight velocity of the mass motions amounted to several tens of km s–1 in some Na i D emitting prominences investigated. The life time of the phenomena is estimated to be about several tens of minutes.  相似文献   

4.
We discuss the longitudinal component of the magnetic field, B , based on data from about 135 quiescent prominences observed at Climax during the period 1968–1969. The measurements are obtained with the magnetograph which records the Zeeman effect on hydrogen, helium and metal lines. Use of the following lines, H; Hei, D3, Hei, 4471 Å; Nai, Di and D2, leads to the same value for the observed magnetic field component in these prominences. For more than half of the prominences their mean field, B , satisfy the inequalities 3 G B 8 G, and the overall mean value for all the prominences is 7.3 G. As a rule, the magnetic field enters the prominence on one side and exits on the other, but in traversing the prominence material, the field tends to run along the long axis of the prominence.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

5.
A sequence of images taken at different positions in the resonance lines of Ca ii, Mg ii, and H i was obtained over a quiescent prominence with the LPSP instrument on OSO-8. Ca ii K (and H) profiles are reconstructed at different locations in the prominence with a (10 × 5) arc sec2 resolution. Significant variations of FWHM and line shifts are found: FWHM range from 0.14 Å to 0.5 Å; blue shifts reach about 14 km s-1. The ratio of K to H absolute intensities shows a large spread around the average value of 1.2. The same ratio for the Mg ii lines in the whole prominence is higher (1.7), a fact already noticed at the edge of an active prominence (Vial et al., 1979). The ionization degree, as measured by the L/Ca K ratio, shows noticeable variations within the prominence. The L intensity is about 0.3 times the intensity measured in the quiet Sun, and the L/L ratio is less than one half the disk value. These results indicate important variations of the thermal conditions inside the prominence.DASOP, Observatoire de Paris, 92190 Meudon, France.  相似文献   

6.
With thespectro-coronagraph and themultichannel subtractive double pass spectrograph (MSDP) at the Pic du Midi Observatory two quiescent prominences were observed simultaneously. From the spectro-coronagraph observations 2D maps of Hei 10830 , Fexiii 10798 and 10747 line intensities were obtained. In addition, we obtained 2D maps of the ratioR of the two iron lines. This ratio is used as a diagnostic for determining the density of the hot coronal plasma surrounding prominences. We found that the electron density is higher at the location of the prominences than in the corona, whereas small regions (40) of lower electron density are unevenly distributed around the prominences indicating that the surrounding corona is highly inhomogeneous. The density of the cavity is reduced by a factor 1.5 compared to the density of the prominence environment (5 × 108 cm–3). We discuss the existence of cavities around these prominences according to the orientation of their axes relative to the line of sight and according to the velocity field inside the prominences. Constraints on models for prominence formation are derived.  相似文献   

7.
We scanned the H i L, Mg ii h and k, Ca ii K and H lines simultaneously with the LPSP instrument on OSO-8, to investigate the low and moderate temperature regions of an active region filament. The L line is not reversed except for the innermost position in the prominence. Intensity (k/h), (K/H) ratios are respectively 2 and 1.1, indicating that the Mg ii lines are optically thin, and that Ca ii K is saturated, although not clearly reversed. The results obtained during the second sequence of observations (K saturated before L for example) indicate that within the size of the slit (1 × 10) we are not observing the same emitting features in the different lines.We also observe an important line-of-sight velocity at the outer edge of the feature, increasing outwards from a few km s–1 to 20 km s–1 within 2. Less than half an hour later, this velocity is reduced to 15 km s–1 while the intensities increase. Full width at half maximum intensities for this component indicate turbulence variations from 22 to 30 km s–1. The observed high velocities at the top of the prominence can be compared with radial velocities that Mein (1977) observed in H at the edges of an active filament and interpreted as velocity loops slightly inclined on the axis of the filament.  相似文献   

8.
A study of the metallic lines in bright quiescent prominences indicates that the optical thickness in the K line of Ca ii may reach values as high as 103. This is about 10 times larger than the optical thickness in the H line and may explain some peculiarities of the H and K lines in solar prominences.  相似文献   

9.
We use the polarimetric and intensity measurements of H and HeI D3 lines in solar prominences to derive the true geometrical thickness for several quiescent prominences. The electron densities, derived from the collisional depolarization in H by Bommier et al. (1994), are used to evaluate the thickness from the emission measure. The emission measure was obtained from the theoretical correlation with the H integrated intensity, according to Gouttebroze, Heinzel, and Vial (1993). Theoretical electron densities obtained by latter authors are also compared with those of Bommier et al. (1994) and we find a very good agreement between them. The prominence geometrical thickness exhibits a relatively large range of values from about 100 km up to a few 104 km. The plasma densities vary by almost two orders of magnitude in the observed structures, but the total column mass in the direction perpendicular to the prominence sheet seems to be fairly constant for the set of prominences studied.  相似文献   

10.
Spectroscopic observations of the Nai D emission lines of prominences were made with the Domeless Solar Telescope in Hida Observatory. When active prominences are bright in the D2 emission line, the intensity ratio of D1 to D2 is found to deviate significantly from the theoretical ratio of the optically-thin case. On the other hand, the intensity ratio is close to the theoretical ratio for the most part of quiescent prominences. Furthermore, the full widths at half maximum intensity of the D2 emission line for active prominences become wider than those of the D1 line, as the intensity of the D2 line gets higher. These observed features clearly show that the emitting region of the Nai D lines is optically thick in some types of prominences. Non-LTE calculations were made by taking the ionization degree of hydrogen atoms and the thickness of the prominences and the electron temperature as free parameters. It is shown that the electron temperature of the emitting region of the Nai D lines should be as low as 4000 K for an explanation of the large optical thickness of the Nai D lines for active prominences. Brief discussions are included about the possible existence of low temperatures in active prominences.  相似文献   

11.
A. Poland  U. Anzer 《Solar physics》1971,19(2):401-413
The energy balance for cool quiescent prominences is examined using a 6000 km, 6000 K isothermal slab model prominence with a density gradient dictated by a modified Kippenhahn-Schlüter model. The model is irradiated from both sides by the coronal, chromospheric, and photospheric radiation fields. The radiative transfer problem is solved in detail for the Lyman continuum and H to determine the net radiative energy loss for hydrogen. An estimate of the energy loss for Ca ii H and K indicates that this source of energy loss is unimportant when compared with the hydrogen radiation. The radiative energy loss is easily balanced by the conductive energy gain from the corona.The only difficulty with our model is that the total hydrogen density must be of the order of 3 × 1012/ cm3 to match the n = 2 population density of 5 × 104/cm3 obtained from observation. To support a prominence of this density and a thickness of 6000 km against gravity requires magnetic fields of the order of 20 G which is much higher than the average magnetic field in quiescent prominences deduced from limb observations. Two possible explanations for this discrepancy are given.Currently at the Max-Planck-Institut für Physik und Astrophysik, München, Germany.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

12.
Radio images and spectra of an eruptive prominence were obtained from simultaneous multifrequency observations at 36 GHz, 89 GHz, and 110 GHz on May 28, 1991 with the 45-m radio telescope at Nobeyama Radio Observatory (NRO), the National Astronomical Observatory, Japan (NAOJ). The radio spectra indicated that the optical depth is rather thick at 36 GHz whereas it is thin at 89 and 110 GHz. The H data, taken at Norikura Solar Observatory, NAOJ, suggest that the eruption of an active region filament was triggered by an H flare. The shape and position of the radio prominence generally coincided with those of H images. The radio emission is explained with an isothermal cool thread model. A lower limit for the electron temperature of the cool threads is estimated to be 6100 K. The range of the surface filling factors of the cool threads is 0.3–1.0 after the H flare, and 0.2–0.5 in the descending phase of the eruptive prominence. The column emission measure and the electron number density are estimated to be of the order of 1028 cm–5 and 1010 cm–3, respectively. The physical parameters of a quiescent prominence are also estimated from the observations. The filling factors of the eruptive prominence are smaller than those of the quiescent prominence, whereas the emission measures and the electron densities are similar. These facts imply that each cool thread of the prominence did not expand after the eruption, while the total volume of the prominence increased.  相似文献   

13.
We compare observations of an eruptive and a quiescent prominence in order to better understand the energetic processes in an eruptive prominence. Observations of an eruptive prominence were obtained in H, several UV emission lines (1215–1640 Å), and coronal white light at approximately 19:00 UT on September 20, 1980. The data we present shows the development of the eruption in the H and UV emission lines and is compared with the intensities from similar observations of a quiescent prominence. While the event is coincident with some coronal changes, above 1.2 and up to 1.5 solar radii, it does not result in a true coronal mass ejection event.The comparison between the eruptive and quiescent prominences reveals several differences which suggest that the activation consists not only of a mechanical movement of material, but also changes in the temperature of the prominence plasma. Some prominence material that does not seem to participate in the large scale prominence motion is heated during the eruptive event. Most of this material is heated to transition zone temperatures with almost no cool core (i.e., no or very little H emission). The behavior indicates that there are structures that are first cool and then heat up to transition zone temperatures (apparently remaining stable for some time at these temperatures). Since this is an unstable temperature region for prominence type structures the energy transport that allows this is not understood and presents an interesting theoretical problem.Member of the Carrera del Investigador, CONICET, Argentina, presently at The University of Alabama in Huntsville.  相似文献   

14.
Helical structures are generally associated with many eruptive solar prominences. Thus, study of their evolution in the solar atmosphere assumes importance. We present a study of a flare-associated erupting prominence of March 11, 1979, with conspicuous helically twisted structure, observed in H line center. We have attempted to understand the role played by twisted force-free magnetic fields in this event. In the analysis, we have assumed that the helical structures visible in H outline the field lines in which prominence tubes are embedded. Untwisting of observed prominence tubes and later, formation of open prominence structures provide evidence of restructuring of the magnetic field configuration over the active region during the course of prominence eruption. Temporal evolution of the force-free parameter is obtained for two main prominence tubes observed to be intertwined in a rope-like structure. Axial electric currents associated with the prominence tubes are estimated to be of the order of 1011 A which decreased with time. Correspondingly, it is estimated that the rate of energy release was 1028 erg s–1 during the prominence eruption.  相似文献   

15.
Stellmacher  G.  Wiehr  E. 《Solar physics》2000,196(2):357-367
Emission lines from quiescent prominences were observed simultaneously through narrow-band interference filters, thus integrating the total line intensities without the use of a spectrograph. Simultaneous exposures (50 ms) on three electronically connected CCD cameras at the 70 cm VTT on Tenerife assured almost identical influence of the Earth's atmosphere and a spatial resolution of 1 arc sec. The resulting spatially high-resolution two-dimensional images in H, H, and Ca+8542, calibrated in units of the disk-center intensities, allow a two-dimensional mapping of emission ratios yielding relevant physical parameters. The emission relation between H and H, which depends on the total optical thickness, confirms earlier photometric results from spectra, however, with a large sample of data points from six prominences. It demonstrates the saturation effects towards brighter prominences or prominence locations. The relation between Ca+8542 and H, which depends on the gas pressure, is found to vary between different prominences but is nearly constant within one prominence. Its mean spatial variation of 30% within one prominence may be interpreted in terms of a magnetic field with variations of 5%. The brightness distribution in most prominences is not smooth but indicates preferred values, which are interpreted as superpositions of several fine structures.  相似文献   

16.
The potential models of the unipolar sunspot magnetic field are calculated on the basis of magnetographic measurements of the magnetic field made in the three spectral lines of different intensities, H, Cai 6103 and Fei 4808. The computed distributions of the magnetic field vector are compared with actual distributions observed at these three levels. It is shown that the electric current density in the spot reaches values up to 105 CGSE in the volume contained between formation depths of two pairs of lines, Fei 4808-Cai 6103 and Fei 4808 - H. Therefore, the magnetic field of the spot deviates strongly from a potential configuration. To the contrary, at higher levels, in the semi-infinite volume restricted at the bottom by the hydrogen H-line, the field appears to be quite close to a potential one.  相似文献   

17.
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   

18.
A spectroscopic investigation of a quiescent prominence has been performed: the line profiles of the H and K lines have been carefully determined in all regions of the prominence where these emissions are likely to originate in optically thin layers. Therefore we have been able to study the electron temperature T e and the microturbulent velocity in the outer parts of the prominence. We find that on the average, T e = 5700 K (Figure 1) and = 6.7 km s-1 (Figure 2) which are in very good agreement with classical data. Figure 3 represents the radial velocity measurements and Figure 4 the ratio of the total intensity of H to K lines. Thus the prominence we have observed does not show for T e and the regular increase outward which has been described by Hirayama (1971). On the other hand increases towards the Equator, in the dynamically active part of the prominence, which could indicate that represents the effect of macroturbulence rather than microturbulence (Kawaguchi, 1966). In this part of the prominence only the K line is in emission and the average value of the microturbulence is 9.4 km s-1, the radial velocity is also generally increasing. At last, according to the absolute intensities of the H and K lines, the electron density in the outer layers of the prominence is no more than 1 × 1010 cm-3.  相似文献   

19.
The fine structure of nonspot prominences are studied from H filtergrams. The size of the smallest prominence structures increases with height above the chromosphere. Some prominences contain structures close to 1/2 arc second, which is the spatial resolution in the present data. The effective thickness of many nonspot prominences ranges between 4 × 107 cm and 1.5 × 108 cm. An apparent downward directed motion is observed in the majority of the prominences. No preferred direction of the motion is seen in regions composed of comparatively large diffuse structures. Some bright threads are visible for 1 hr and longer. Bright knots have an average observed lifetime of about 8 min. The process of condensation and subsequent destruction of prominence fine structure appears to take place on a very short time scale compared to the life time of the regions where prominences may exist. The observed H brightness of the prominences in the present data may be accounted for as scattered chromospheric radiation.  相似文献   

20.
High-resolution spectroscopic monitoring of the Nai D lines in the T Tau-type star RY Tau results in the discovery of relatively cool gas clouds ascending and descending inside the stellar wind on a time-scale of few days and co-rotating with the star. Radial velocity of the clouds varies from –100 to +100 km s–1, which is twice as large as thev sini of the star.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   

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