首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 62 毫秒
1.
We report measurements of line intensities and line widths for three quiescent prominences observed with the Naval Research Laboratory slit spectrograph on ATM/Skylab. The wavelengths of the observed lines cover the range 1175 Å to 1960 Å. The measured intensities have been calibrated to within approximately a factor 2 and are average intensities over a 2 arc sec by 60 arc sec slit. We derive nonthermal velocities from the measured line widths. The nonthermal velocity is found to increase with temperature in the prominence transition zone. Electron densities and pressures are derived from density sensitive line ratios. Electron pressures for two of the prominences are found to lie in the range 0.04–0.08 dyn cm–2, while values for the third and most intense and active of the three prominences are in the range 0.07–0.22 dyn cm–2.  相似文献   

2.
Wilhelm  K.  Lemaire  P.  Curdt  W.  Schühle  U.  Marsch  E.  Poland  A. I.  Jordan  S. D.  Thomas  R. J.  Hassler  D. M.  Huber  M. C. E.  Vial  J.-C.  Kühne  M.  Siegmund  O. H. W.  Gabriel  A.  Timothy  J. G.  Grewing  M.  Feldman  U.  Hollandt  J.  Brekke  P. 《Solar physics》1997,170(1):75-104
SUMER – the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) – observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar coronal hole. Using detector A of the instrument, this range was later extended to 1610 Å. The second-order spectra of detectors A and B cover 330 to 805 Å and are superimposed on the first-order spectra. Many more features and areas of the Sun and their spectra have been observed since, including coronal holes, polar plumes and active regions. The atoms and ions emitting this radiation exist at temperatures below 2 × 106 K and are thus ideally suited to investigate the solar transition region where the temperature increases from chromospheric to coronal values. SUMER can also be operated in a manner such that it makes images or spectroheliograms of different sizes in selected spectral lines. A detailed line profile with spectral resolution elements between 22 and 45 mÅ is produced for each line at each spatial location along the slit. From the line width, intensity and wavelength position we are able to deduce temperature, density, and velocity of the emitting atoms and ions for each emission line and spatial element in the spectroheliogram. Because of the high spectral resolution and low noise of SUMER, we have been able to detect faint lines not previously observed and, in addition, to determine their spectral profiles. SUMER has already recorded over 2000 extreme ultraviolet emission lines and many identifications have been made on the disk and in the corona.  相似文献   

3.
Singh  Jagdev  Sakurai  Takashi  Ichimoto  Kiyoshi  Muneer  S. 《Solar physics》2003,212(2):343-359
Spectra around the 6374 Å [Fex] and 7892 Å [Fexi] emission lines were obtained simultaneously with the 25-cm coronagraph at Norikura Observatory covering an area of 200 ×500 of the solar corona. The line width, peak intensity and line-of-sight velocity for both the lines were computed using Gaussian fits to the observed line profiles at each location (4 ×4 ) of the observed coronal region. The line-width measurements show that in steady coronal structures the FWHM of the 6374 Å emission line increases with height above the limb with an average value of 1.02 mÅ arc sec–1. The FWHM of the 7892 Å line also increases with height but at a smaller average value of 0.55 mÅ arc sec–1. These observations agree well with our earlier results obtained from observations of the red, green, and infrared emission lines that variation of the FWHM of the coronal emission lines with height in steady coronal structures depends on plasma temperatures they represent. The FWHM gradient is negative for high-temperature emission lines, positive for relatively low-temperature lines and smaller for emission lines in the intermediate temperature range. Such a behaviour in the variation of the FWHM of coronal emission lines with height above the limb suggests that it may not always be possible to interpret an increase in the FWHM of emission line with height as an increase in the nonthermal velocity, and hence rules out the existence of waves in steady coronal structures.  相似文献   

4.
Images of a flare and active regions were obtained in the extreme ultraviolet emission lines such as CIII 977 Å, Ne VIII 770 Å, and HI L, and hydrogen Lyman continua with a spatial resolution of less than ten seconds of arc together with one-dimensional scanning at 1650 Å. A microchannel plate was used as a detector, and pointing accuracy was, for about half of the observation time, around 0.5 arc sec.The relationship between the shape of the flare and the structure of the photospheric magnetic field is discussed. A map of the electron temperature distribution derived from the intensity ratio of the Lyman continua at 880 Å and 815 Å showed a lower temperature in regions of higher activity. A very small geometrical thickness of 50–500 m in the C III emitting region of the flare was found. And the layer emitting the continuum in 1650 Å is shown to be at a temperature of 5300 K in the flare and 4700 K in active regions.  相似文献   

5.
Measurements of the solar X-ray spectrum between 3 Å and 15 Å are reported. They were made with two slitless Bragg crystal spectrometers flown on a Sun-pointed Skylark rocket on 8 August, 1967.The use of a beryl crystal has provided higher spectral resolution than hitherto in the spectral range 12 Å and 15 Å leading, in particular, to a revised identification of the strong line at 13.71 Å. Separate components of the stronger emission lines are clearly seen from each of three coronal active regions which may be identified on radio and X-ray spectroheliograms.The absolute line fluxes are used to determine a model for each active region in terms of the differential emission measure as a function of electron temperature. Emission lines due to the transition 1s 2 1 S 0 – 1s2s 3 S 1 in several helium-like ions are identified and values of the local electron density derived from measurement of the line flux in these ions.  相似文献   

6.
A spectrum of Mars of unprecedented quality was obtained in the range of 904-1183 Å with a spectral resolution of 0.2 Å using the Far Ultraviolet Spectroscopic Explorer. Besides marking the first detection of molecular hydrogen on Mars (Krasnopolsky and Feldman, Science 2001 294, 1914-1917), the spectrum also revealed many emission lines of H, O, N, C, Ar, He, N+, C+, and Ar+ and the bands of N2 and CO. The spectrum makes it possible to study the emission multiplet structures and the component ratios and to separate many of the blended lines. From the argon lines, we retrieved Ar mixing ratios of 1.5 and 1.3% at 150 and 130 km, respectively, in excellent agreement with the Viking mass spectrometric measurements of 1.6% in the lower atmosphere. The He 584-Å emission observed in second order also agrees with the Extreme Ultraviolet Explorer detection of He on Mars. The observed spectrum may be used as a database to study specific problems such as the dayglow excitation, radiative transfer, and composition in Mars' upper atmosphere.  相似文献   

7.
Magnetic-field structure of the photospheric network   总被引：2，自引：0，他引：2  
A method is developed to determine the physical parameters of the spatially unresolved photospheric network. The apparent magnetic fluxes are recorded simultaneously in the two FeI lines 5250 and 5247 Å, which belong to the same multiplet and have practically the same oscillator strength and excitation potential of the lower level, but differ in the effective Lande factor. By analysing magnetograph recordings in this pair of lines together with simultaneous recordings in the two FeI lines 5250 and 5233 Å, it is possible to separate the effects on the line profiles due to Zeeman splitting and temperature enhancement in the network.From an analysis of the observations the following properties of the photospheric network are obtained: Field strengths of about 2000 G are present in the network in quiet regions. The characteristic size of the magnetic-field structures in the network appears to be in the range 100–300 km. The 5250 Å line is weakened by roughly 50% in the network. If the line had been non-magnetic, the weakening would have been about 20%. The rest of the weakening is caused by the strong Zeeman splitting. The downward velocity at the supergranular cell boundaries is estimated to be of the order of 0.5 km s-1.  相似文献   

8.
Ellerman bombs, also called moustaches, are transient brightenings at tiny (< 1 arc sec) points in the lower chromosphere whose spectra are characterized by elongated emission wings on the hydrogen Balmer lines. Babin and Koval recently found linear polarization as high as 20% in bombs, but no physical process that could produce such a high degree of polarization was suggested. A new observational study of polarization in Ellerman bombs is reported here. Images of 32 bombs were obtained with a digital video system viewing the Sun through a 6 Å filter at the Sacramento Peak Vacuum Tower Telescope. A novel polarizing beamsplitter divided each image into two interleaved polarized components which passed simultaneously through a single set of optics and were separated only during data analysis. The sensitivity threshold of the measurements was 1%. In 4 cases out of 32, linear polarization above 2% was detected. The higher incidence of > 2% polarization reported by Babin and Koval is not confirmed.  相似文献   

9.
The time structure and intensity of OSO-6 observations of EUV bursts were studied in relation to the corresponding 10–1030 Å enhancements deduced from SFD data. Impulsive EUV emissions from lines normally emitted from either the chromosphere or from the chromosphere-corona transition region rise simultaneously with the 10–1030 Å flash, to within the time resolution of the OSO-6 observations. Mg × 625 Å also showed concurrent impulsive emissions and a close intensity relation to the 10–1030 Å enhancement. The observational results are consistent with the hypothesis that most of the EUV radiation is being produced thermally in a region of chromospheric density, which is being heated by collisional losses of nonthermal electrons.  相似文献   

10.
Identifications are proposed for twenty of the twenty-eight coronal lines observed in the spectra obtained during a rocket flight into the path of the 7 March, 1970 solar eclipse. The methods by which the lines have been identified are discussed. Most of the lines identified are from forbidden transitions between levels in the ground 2p n and 3p n configurations in high ions of magnesium, silicon, sulphur, iron, and nickel. The temperature range represented is from 6.9 × 105 K to 2.5 × 106 K. The classification of three lines of Fexii and two of Nixiv has led to a revised identification for the near ultraviolet 2 D 3/2-2 P 1/2 transition in Fe xii. This transition can be identified with the line at 3072 Å rather than that at 3021 Å as previously suggested in the literature.  相似文献   

11.
We describe an instrument we have built and installed at Mees Solar Observatory on Haleakala, Maui, to measure polarization in narrow-band solar images. Observations in Zeemansensitive photospheric lines have been made for nearly all solar active regions since the instrument began operations in 1992. The magnetograph includes a 28-cm aperture telescope, a polarization modulator, a tunable Fabry-Pérot filter, CCD cameras and control electronics. Stokes spectra of a photospheric line are obtained with 7 pm spectral resolution, 1 arc sec spatial resolution over a field 4.7 arc min square, and polarimetric precision of 0.1%. A complete vector magnetogram observation can be made every eight minutes. The flexibility of the instrument encourages diverse observations: besides active region magnetograms we have made, for example, composite vector magnetograms of the full solar disk, and H polarization movies of flaring regions.  相似文献   

12.
In the Coudé focus of the 2 m RCC telescope at the National Astronomical Observatory of the Bulgarian Academy of Science 47 spectrograms covering the range from 3500 to 4900 Å (about 1400 Å) with a reciprocal dispersion of 9 Å mm–1 and a spectral resolution of 0.18 Å were obtained. The photometric and position behaviour of Balmer lines were investigated over a long time-scale, i.e. March 1981 to August 1982.The hydrogen line profiles were rectified in the way discribed by de Groot (1969). It is found that the absorption consists of three and sometimes four components. Their position behaviour may be expalined by the existence of two kinds of shells: pulsating and steadily expanding, and it is quite possible that shells of the first type may become shells of the second type in the outer parts of the P Cyg envelope.The total emission and absorption equivalent widths of the H11, H9, and H lines change with conspicuous minima and maxima. The amplitude of these variations increases with decrease in the upper quantum number. For example,W tot abs change by about 38% for H and 22% for H9.Our data suggest a periodic change in the radial velocities, intensity of each separate absorption component, total equivalent widths and profiles.  相似文献   

13.
Scanning spectrometer measurements in the range 1310–270 Å, observed from the satellite OSO 3, are reported for the solar flare of 2114 UT March 27, 1967. This flare was a long lasting sequence of bursts with EUV spectra consisting of enhanced lines and recombination continua normally emitted from the chromosphere and chromosphere-corona transition region, with unusually small increases in lines normally emited from the corona. An EUV flare spectrum is presented and suggested as one example for interpreting broadband observations of EUV bursts. Any broadband continuum other than known recombination continua contributed less than 6 % of the meassured line and hydrogen recombination continua in the range 270–1310 Å. The ratio of photon flux of Ciii 1176 Å to that of Ciii 977 Å was 0.86, which suggests an ambient density in the region of emission greater than 1012 cm-3 at temperatures near 60000 K.  相似文献   

14.
Results are presented for several theoretical line ratios in Nev involving transitions between multiplets in the 2s 22p 2 and 2s2p 3 configurations. A comparison of these with solar data from the S082A and S-055 instruments on board Skylab reveals generally good agreement between theory and experiment, especially in the case of the high-resolution (S082A) observations. However the 2s 22p 2 1 D – 2s2p 3 1 P (365.6 Å) and 2s 22p 2 3P – 2s2p 3 3 S (359 Å) lines appear to be blended, possibly with transitions in Fex and Fexi/Fexiii, respectively. We note that the intensity ratio I(365.6 Å)/I(416.2 Å) should be a valuable calibration check for a high-resolution extreme ultraviolet instrument in the spectral range 360–420 Å.  相似文献   

15.
H.M. Schmid  F. Joos  D. Gisler 《Icarus》2011,212(2):701-713
We present ground-based limb polarization measurements of Jupiter and Saturn consisting of full disk imaging polarimetry for the wavelength 7300 Å and spatially resolved (long-slit) spectropolarimetry covering the wavelength range 5200-9350 Å.For the polar region of Jupiter we find for λ = 6000 Å a very strong radial (perpendicular to the limb) fractional polarization with a seeing corrected maximum of about +11.5% in the South and +10.0% in the North. This indicates that the polarizing haze layer is thicker at the South pole. The polar haze layers extend down to 58° in latitude. The derived polarization values are much higher than reported in previous studies because of the better spatial resolution of our data and an appropriate consideration of the atmospheric seeing. Model calculations demonstrate that the high limb polarization can be explained by strongly polarizing (p ≈ 1.0), high albedo (ω ≈ 0.98) haze particles with a scattering asymmetry parameter of g ≈ 0.6 as expected for aggregate particles of the type described by West and Smith (West, R.A., Smith, P.H. [1991]. Icarus 90, 330-333). The deduced particle parameters are distinctively different when compared to lower latitude regions.The spectropolarimetry of Jupiter shows a decrease in the polar limb polarization towards longer wavelengths and a significantly enhanced polarization in strong methane bands when compared to the adjacent continuum. This is a natural outcome for a highly polarizing haze layer above an atmosphere where multiple scatterings are suppressed in absorption bands. For lower latitudes the fractional polarization is small, negative, and it depends only little on wavelength except for the strong CH4-band at 8870 Å.The South pole of Saturn shows a lower polarization (p ≈ 1.0-1.5%) than the poles of Jupiter. The spectropolarimetric signal for Saturn decrease rapidly with wavelength and shows no significant enhancements in the fractional polarization in the absorption bands. These properties can be explained by a vertically extended stratospheric haze region composed of small particles <100 nm as suggested previously by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M. [2005]. Icarus 179, 195-221).In addition we find in the V- and R-band a previously not observed strong polarization feature (p = 1.5-2.0%) near the equator of Saturn. The origin of this polarization signal is unclear but it could be related to a seasonal effect.Finally we discuss the potential of ground-based limb polarization measurements for the investigation of the scattering particles in the atmospheres of Jupiter and Saturn.  相似文献   

16.
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   

17.
The purpose of this paper is to report on some intensity measurements of the Fe xiii lines at 10 747 Å and 10 798 Å made during the total eclipse of 12 November, 1966. Infrared spectra were taken of the solar corona at a dispersion of 90 Å per mm, using an RCA image converter and spectrograph aboard the NASA CV 990 aircraft off the coast of southern Brazil. The spectra have been reduced to equivalent width in terms of the coronal continuum and values derived for different points in the corona.The observed equivalent widths of the lines lie in the range 10 to 30 Å for the 10 747 line and 5 to 12 Å for the 10 798 line. The ratio of these equivalent widths is found to vary from 2.3 in the inner corona to 6 at a point 1.36 solar radii from the center of the Sun.The above results are discussed in terms of the excitation mechanisms involved in producing the lines. In particular, the results are compared with the recent theoretical calculations of Chevalier and Lambert, who are the first to include the effects of proton collisions in the excitation of the 3p 2 3 P levels of Fexiii. Our observations are consistent with an electron density of 4 × 108 in the inner corona; a value which compares favorably with those derived by other observers from the strength of the K continuum. These are, to our knowledge, the first eclipse observations of the infrared Fe xiii lines which indicate that proton collisions are important in the excitation of the coronal lines. The coronal abundance of iron is estimated from the equivalent width of the 10 747 line, and in common with other observers we find an overabundance as compared to the photospheric abundance by a factor of 10.  相似文献   

18.
Wavelengths of clean atmospheric water lines, and some solar lines, in the wavelength interval 10750 Å to 10900 Å have been measured to an accuracy approaching ± 1 mÅ. Strengths and wavelengths have been measured for all atmospheric water lines with absorption coefficients > 5 × 10–4 cm–1 gm–1 cm–2 at 280K, that lie within 15 Å of the He I 10830 Å featur of the stronger He component is affected by a weak water line which reduces atmospheric transmission by nearly 1 % with 10 mm precipitable water in the line of sight.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

19.
A preliminary radial velocity of 13 Mon and the redshift caused by the scattering of photons in its chromosphere are given. They have been obtained from the wavelengths of 39 spectral lines, measured in 2 spectra and the corresponding halfwidth measured in 4 spectra, taken in 1980 with a dispersion of about 9 Å/mm. (1 Å = 0.1 nm), in the range 3700 Å-5000 Å.  相似文献   

20.
R-matrix calculations of electron impact excitation rates in N-like Mgvi are used to derive theoretical electron-density-sensitive emission line ratios involving 2s 22p 3–2s2p 4transitions in the 269–403 Å wavelength range. A comparison of these with observations of a solar active region, obtained during the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals good agreement between theory and observation for the 2s 22p 3 4 S–2s2p 4 4 Ptransitions at 399.28, 400.67, and 403.30 Å, and the 2s 22p 3 2 P–2s2p 4 2 Dlines at 387.77 and 387.97 Å. However, intensities for the other lines attributed to Mgvi in this spectrum by various authors do not match the present theoretical predictions. We argue that these discrepancies are not due to errors in the adopted atomic data, as previously suggested, but rather to observational uncertainties or mis-identifications. Some of the features previously identified as Mgvi lines in the SERTS spectrum, such as 291.36 and 293.15 Å, are judged to be noise, while others (including 349.16 Å) appear to be blended.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号