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1.
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   

2.
We present measurements of electric fields in quiescent prominences and in a small flare surge, obtained with the CRI electrograph at the NSO/SP 40 cm coronagraph, in 1993 and 1994. Our results on the 9 brightest quiescent prominences enable us to place r.m.s. upper limits ofE t < 2 – 5 V cm–1 on the component ofE transverse to the line of sight. We show that these upper limits may be difficult to reconcile with non-ideal MHD models of quiescent prominences formed in extended neutral sheets, whether or not the tearing mode instability is present. They do, however, seem consistent with ideal MHD models of prominence support. We point out also that these upper limits are within a factor 4 of the minimum value of anistropic electric field that exists due to motional Stark effect in any thermal plasma permeated by a directed magnetic field.Our data on the flare surge suggest an electric field of intensityE 35 V cm–1, oriented approximately parallel to the inferred magnetic field. This detection ofE needs to be verified in other flares. But we note that a detectableE would not be expected in the current interruption flare mechanism, if only a single double layer is present. We show further that the observed relatively narrow, approximately-Gaussian, and only slightly Doppler-shifted Paschen lines, seem inconsistent with the multiple double layers invoked in other models based on the current interruption mechanism. Our detection ofE does seem consistent with reconnection (including tearing-mode) models of flares, provided the field-aligned electrical conductivity is anomalous over substantial volumes of the plasma circuit joining the reconnecting domain to the photosphere.  相似文献   

3.
A very low upper limit of 0.15 mÅ for the interstellar 6707 Å Lii line has been recently derived towards the SN1987a by Baade and Magain (1988). This value corresponds toN(Li)<1.4×1011 cm–2 and gives [Li/H]<5.4×10–11 assumingN(Hi)=2.6×1021 cm–2 for the hydrogen column density in the LMC towards SN1987a. This value is lower than the Li abundance found in the Population II stars and lower than the minimum abundance allowed in the framework of the standard Big-Bang theory. We indirectly estimate the Li depletion usingKi observations and show that a depletion of 1.2 dex is plausible. Therefore, an interstellar abundance [Li/H] as high as 0.8×10–9 cannot be excluded. Any improvement in the above-mentioned upper limit will place important constraints on current theories for lithium nucleosynthesis.High-resolution IUE spectra of the SN1987a have been analysed in search for IS 1362 ÅBii resonance lines. A minimum detectable equivalent width of 22 mÅ has been found, that impliesN(B)<1.2×10–12 cm–2 and [B/H]<4.7×10–10 cm–2, i.e., comparable to the solar value of [B/H]=4×10–10. This limit is the most stringent derived so far for an external galaxy, and suggests that the rate of spallation processes in the LMC has not been higher than in our own Galaxy.  相似文献   

4.
Results are given of the detailed analysis of fourteen Fe xxv-xxiii lines ( = 1.850–1.870 Å) in the spectra of a solar flare on 16 Nov. 1970. The spectra were obtained with a resolution of about 4 × 10–4 Å, which revealed lines not previously observed and allowed the measurement of line profiles. The measured values of the wavelengths and emission fluxes are presented and compared with theoretical calculations. The analysis of the contour of the Fe xxv line ( = 1.850 Å) leads to the conclusion that there is unidirectional macroscopic gas motion in the flare region with the velocity (projection on the line of sight) ± 90 km s–1.Measurements of the 8.42 Å Mg xii and 9.16 Å Mg xi lines in the absence of solar flares indicate prolonged existence of active regions on the solar disk with T e = 4–6 × 106K and emission measure ME 1048 cm–3. The profile of the Mg xii line indicates a macroscopic ion motion with a velocity up to 100 km s–1.  相似文献   

5.
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   

6.
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   

7.
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   

8.
Previously published solar abundances of oxygen and carbon can be corrected to be logN(O) = 8.93 and logN(C) = 8.60 on the hydrogen log-scale when new accurate forbidden electric quadrupole transition probabilities A Q(s–1) are used. Such A Q's, based on the new atomic structure and electron correlation theory, developed recently by Sinanolu and coworkers, are reported for the (1 S 0-1 D 2) lines of [C i], [N ii, [O i] and [O iii] and the (2 P-2 D) lines of [N i] and [O ii]. The available experimental values are also given for comparison.Work supported by Grant No. GP-29471 from the U.S. National Science Foundation.  相似文献   

9.
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   

10.
Eclipsing binary TX UMa was observed with the D.A.O. high-dispersion spectrographs in 1969–1970, with emphasis on the detailed coverage of the primary minimum. One spectrum was taken exclusively within totality, thus exhibiting an uncontaminated spectrum of the secondary component. This leads to spectral reclassification of the secondary (F6 IV). The narrowing of the line profile of the H-line in totality is interpreted in terms of synchronous rotation of the secondary (v sini80 km s–1) while the primary rotates faster (v sini130 km s–1) than synchronously (v sini50 km s–1). Although the secondary does not fill in its Roche lobe fully, the system exhibits pronounced indications of rather strong physical interaction. This is now supported also by the profound changes of the line profiles of the H-line with phase.  相似文献   

11.
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   

12.
On 23 May 1967 energetic (10–50 keV) solar flare X-rays were observed by the OGO-III ion chamber during the period 1808–2100 UT. The time-intensity profile for the X-ray event showed three distinct peaks at 1810, 1841 and 1942 UT. The second peak, which is equivalent to 2.9 × 10–3 ergs cm–2sec–1 above 20 keV, is the largest X-ray burst observed so far by the OGO-I and OGO-III ion chambers. The soft (2–12 Å) X-ray observations reported by Van Allen (1968) also show similar peaks, roughly proportional in magnitude to the energetic X-ray peaks. However, the intensity of energetic X-rays peaked in each case 5–10 min earlier than the soft X-ray intensity indicating a relatively hard photon energy spectrum near the peak of the energetic X-ray emission. The corresponding time-intensity profile for the solar radio emission also showed three peaks in the microwave region nearly coincident with the energetic X-ray peaks. The third radio peak was relatively rich in the metric emission. Beyond this peak both the energetic X-rays and the microwave emission decayed with a time constant of 8 min while the corresponding time constant for the soft X-rays was 43 min. In view of the earlier findings about the energetic X-rays it is indicated that the 23 May solar X-ray event was similar to those observed earlier. During the 23 May event the integral energy flux spectrum at the time of peak intensity is found to be consistent with the form e –E/E 0, E 0 being about 3.4 and 3.7 keV for the peaks at 1841 and 1942 UT, respectively. Assumption of a similar spectrum during the decay phase indicates that the spectral index E 0 decreased nearly exponentially with time.The OGO-III ion chamber, which is also sensitive to protons 12 MeV, observed a solar particle event starting at 2100 UT on 23 May. It could not be determined uniquely which of the two principal X-ray peaks was associated with the particle event, and in fact both may have contributed. The particle intensity reached its maximum value at 1003 UT on 25 May 1967. The equivalent peak radiation dosage was 24 R/hour behind the 0.22 g cm–2 thick aluminum wall of the chamber. This peak radiation dosage was considerably smaller than the maximum dosage (60 R/hour) during the 2 September 1966 solar particle event, the largest event observed so far by the OGO-I and OGO-III satellites. The temporal relationship between the solar X-ray and particle events on 23 May 1967 was similar to that observed in the solar flare events on 7 July 1966, 28 August 1966 and 27 February 1967.  相似文献   

13.
T. Moran  P. Foukal 《Solar physics》1991,135(1):179-191
We describe an electrograph instrument designed for measurement of macroscopic electric fields in solar plasmas, using the polarization dependence of line width in Stark-broadened hydrogen Paschen emission lines. Observations of quiescent prominences and limb chromosphere with our electrograph at the NSO/Sac Peak Evans Coronal Facility provide upper limits of 5–10 V cm–1 for transverse macroscopic electric fields in these structures, averaged over an area of about 5 × 7 arc sec. Random thermal motions of hydrogen ions across magnetic field lines generate a quasi-static electric field, which should be distinguishable from pressure broadening in the intensely magnetized chromosphere over a sunspot, given an electrograph sensitivity a factor 2–3 better than that achieved here. Future electrograph measurements of limb flares, post-flare loops and eruptive prominences, even at 5 V cm–1 sensitivity, could provide a useful new test of reconnection and discharge effects in such dynamic structures.  相似文献   

14.
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   

15.
With the aid of the spectra taken in the years 1959–1968, a physical analysis of the atmosphere of P Cygni has been carried out and the motions of the atmosphere have been studied. The variations of radial velocities, the velocity progressions of Balmer and Hei lines, the high rate of mass loss (2×10–5 M yr–1), the features of the observed line profiles, especially that of H-K lines of Caii andD 1-D 2 lines of Nai confirm the conclusion of Van Blerkom (1978), concerning the assumption of an accelerating atmosphere for P Cygni. The electron density variation with the radius seems to ben e r –5/2, with an average value of 7×1011cm–3 at the lower boundary of the atmosphere.In order to explain the two absorption components of observed lines, an atmospheric model based on the assumption of three envelopes, two of which accelerate gradually with two different velocity laws (up to 11.2r c ), and the third of which accelerates rapidly with a standard velocity law (beyond 11.2r c ) has been developed. From this model and the observed profiles, the geometrical thicknesses of the line-forming regions of H, H, H, and H are derived.The observations were obtained at Haute Provence Observatory (CNRS).  相似文献   

16.
Electron impact excitation rates for Fexxi, calculated with theR-matrix code, are used to determine theoretical electron density sensitive emission line ratios involving transitions in the 121–146 wavelength range. The observed ratios for a solar flare, obtained with a grazing spectrometer on board the OSO-5 satellite, imply electron densities which are consistent, with discrepancies that do not exceed 0.3 dex. In addition, the derived values ofN e are similar to those estimated for the high temperature regions of other solar flares. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations.  相似文献   

17.
Hirayama  Tadashi 《Solar physics》1985,100(1-2):415-434
We review observational studies of solar prominences with some reference to theoretical understandings. We lay emphasis on the following findings: (1) An important discovery was made by Leroy, Bommier, and Sahal-Bréchot concerning the direction of the magnetic field inside some high-altitude, high-latitude prominences, where the field vector points in the opposite direction from the one which would be expected from the potential field calculated from the observed photospheric magnetic field. (2) Landman suggests the possibility of a high total density of 10–11 g cm –3 for the main body of quiescent prominences, 50 times higher than the value hitherto believed. (3) Flow patterns, nearly parallel to the magnetic neutral lines, were detected in the 105 K plasma near and in prominences. (4) Coronal loop structures were found overlying prominences as viewed from X-ray photographs. We propose also an evolutionary scheme by taking the magnetic field topologies into account.The fundamental question why a prominence is present remains basically unanswered.  相似文献   

18.
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   

19.
E. Rolli  A. Magun 《Solar physics》1995,160(1):29-40
The analysis of the dynamic evolution of the chromospheric electron density during solar flares is fundamental for the testing of solar flare models. For this purpose we developed a digital imaging spectrograph for the observation of higher Balmer lines below 400 nm with a time resolution of 1 s and an algorithm for the determination of the electron density from the observed line profiles. On January 5, 1992 a M1/1N flare was observed in H, H and Caii H and the temporal evolution of the electron density was determined. The chromospheric electron density rises several times from less than 3 × 1019 to 1 × 1020 m–3 during the hard X-ray peaks.  相似文献   

20.
Morozhenko  N. N. 《Solar physics》1974,34(2):313-322
Observations of the lines He i 3888 and H8 in 80 quiescent prominences by the author, and in other prominences by Kubota et al. (1972) and Morozhenko (1971), have been used to derive the dependences of I(3888)/I(H8) on I(H8), N 2 3 s on 0 (H), and N + n e on 0(H) (Figures 1, 2, 3 and 4). The equations of ionization equilibrium and triplet system steady state for a helium atom (27 levels and continuum were considered) were solved together with the radiation transfer equation in the helium Lyman continuum. As given n e () distribution with depth and T e =7500 K were assumed. The 23 S level population N2 3 s, helium emission measure N + n e and the intensity ratios of the He i 3888 and H8 lines were calculated and compared with observation (Figures 2, 3 and 4, solid lines). The figures show that in bright prominences the observed values of N 2 3 s and N + n e are systematically higher than the calculated ones. These deviations cannot be eliminated by decreasing n e . One can make the calculations and observations agree for bright prominences by increasing the UV radiation which penetrates into the prominence.  相似文献   

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