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1.
Yngve Öhman 《Solar physics》1969,10(1):178-183
During a stay at the Kitt Peak National Observatory the writer has tried to find an influence of flare radiation on the high photospheric and low chromospheric lines of the area occupied by the flare. Observations have been made in the H region and in the region of the H and K lines. When flare emission is present in sunspots some of the faint (molecular) lines seem to be weakened. When a flare appears near the solar limb some of the Evershed-type (chromospheric) lines are strongly influenced.Kitt Peak National Observatory Contribution No. 481.Visiting Astronomer to the Solar Division, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.  相似文献   

2.
Observations of a limb flare and an associated loop prominence were obtained in H with the 512 channel magnetograph of the Kitt Peak National Observatory. Simultaneous radial and torsional oscillations with a period near 75 s, wavelength of 37 000 km, and amplitude of 1–2 km s–1 were detected in the loop approximately 90 min before the onset of the flare. We interpret these coupled oscillations in terms of a kink instability of a current carrying flux tube. The magnitude of the steady-state component of current is estimated to be 6 × 1010 ampères.Visiting Astronomer, Kitt Peak National Observatory, operated by Aura, Inc., under contract with the National Science Foundation.Visiting Student, Kitt Peak National Observatory.  相似文献   

3.
Feature-to-feature identification is made on simultaneous Ca ii K-line spectrograms (SG) and K2v spectroheliograms (SHG). The line profiles in plages and in the network boundary nearly always have double-peaked reversal in the core, while those inside the cells present all possibilities: double-peaked, single-peaked on violet side, single-peaked on red side, and unreversed absorption. Statistics of the profiles in the quiet chromosphere show that 50% are K232 double-peaked, 20% are K2v single-peaked, 10% are K2r single-peaked, and 20% show only incipient reversal or even totally lack any reversal. We call attention to the nontrivial contribution of these absorption profiles which are formed in dark regions shown on SHG's.The physical conditions inferred from different kinds of profiles are briefly discussed.In part to be included in a dissertation to be submitted to the Graduate School, University of Maryland, by S. Y. Liu in partial fulfillment of the requirements for the Ph. D. degree in Astronomy.Visiting Graduate Student, Solar Division, Kitt Peak National Observatory.Visiting Astronomer, Solar Division, Kitt Peak National Observatory.  相似文献   

4.
Mean profiles of eighteen neutral iron lines of varying strengths were measured at selected positions from the center of the solar disk to the limb. These profiles were obtained by rapid photoelectric scanning of the spectrum with a double-pass spectrometer. The Fe i lines selected are representative of most of the stronger low-lying transitions in the neutral iron atom. In addition to the iron lines, this observational program includes center-to-limb measurements of three Ti ii lines and of the Ca i resonance line 4226.7. The line profiles are presented here in graphical form after correction for instrumental effects and normalization to the local disk center continuum.Both Kitt Peak National Observatory and the National Center for Atmospheric Research are sponsored by the National Science Foundation.  相似文献   

5.
Yngve Öhman 《Solar physics》1972,23(1):134-141
From material secured with the McMath Solar Telescope of the Kitt Peak National Observatory rotational (orbital) motion has been found in a prominence ejected from a rotating flare. A period of rotation of 32 min has been derived from the study of a periodic asymmetry of the AL i 3961 absorption line.Presented at the Physics of Prominences-colloquium at Anacapri, September 29, 1971.  相似文献   

6.
A new technique for displaying magnetograph observations is presented and applied to the 12-channel magnetograph at Kitt Peak National Observatory. Using the data from a raster scan, a digital spectroheliogram is constructed on the face of a cathode ray tube and photographed. This enables one to recognize patterns in magnetograph data as easily as with conventional photographs. Comparisons with simultaneous spectroheliograms show no qualitative differences and indicate that the magnetograph is quite capable of studying morphology of individual solar features.Kitt Peak National Observatory Contribution No. 499.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

7.
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   

8.
The small-scale structure of solar magnetic fields has been studied using simultaneous recordings in the spectral lines Fe i 5250 Å and Fe i 5233 Å, obtained with the Kitt Peak multi-channel magnetograph. We find that more than 90% of the magnetic flux in active regions (excluding the sunspots), observed with a 2.4 by 2.4 aperture, is channelled through narrow filaments. This percentage is even higher in quiet areas. The field lines in a magnetic filament diverge rapidly with height, and part of the flux returns back to the neighbouring photosphere. Therefore the strong fields within a magnetic filament are surrounded by weak fields of the order of a few gauss of the opposite polarity. The field-strength distribution within a filament, including the surrounding opposite-polarity fields, seems to be almost the same for all filaments within a given active or quiet region.The analysis of a scan made during an imp. 2 flare showed that observations during and after the flare would give a fictitious decrease of the magnetic energy in the region by a factor of 2–3 due to line-profile changes during the flare.Visiting Astronomer, Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

9.
Measurements of the Sun in the near-infrared He i 10830 Å absorption line were performed using the echelle spectrograph with a dispersion of 6.71 mÅ per pixel at the Vacuum Tower Telescope (German Solar Telescopes, Teide Observatory, Izaña, Tenerife, Spain) on May 26, 1993. These measurements were compared with full-disc soft X-ray images of the Sun (Japanese solar satellite Yohkoh), full-disc solar images in H (Big Bear Solar Observatory), full-disc solar images in the He i 10830 Å line (National Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at 37 GHz (Metsähovi Radio Research Station). In the He 10830 Å line the Sun displays a limb darkening similar to that in the visible part of the spectrum. Active regions and H filaments show a strong absorption in the He 10830 Å line, whereas the absorption is weak in coronal holes.  相似文献   

10.
The use of an auxiliary beamsplitter with the Kitt Peak 15-foot spectroheliograph permits spectroheliograms to be taken simultaneously in 4 identical images of the sun. By using two of these images for a Zeeman spectroheliogram, a third image for a Fei 4071 spectroheliogram, and the fourth image for a 6107Å continuum spectroheliogram, simultaneous measurements of magnetic fields and brightness fields have been obtained. Within the limits of intensity variations imposed by doppler shifts and brightness fluctuations of the continuum, a quantitative relation does exist between the measured values of brightness and magnetic field strength of the photospheric network. For intensities measured +0.12 Å from the core of Fei 4071, this relation is ln(1 +I/I) = ¦B ¦, whereB refers to the component of magnetic field normal to the solar surface,I/I is the fractional excess of brightness of the magnetic regions relative to the brightness of non-magnetic regions, and = (6±2)%/100 gauss.Kitt Peak National Observatory Contribution No. 538.Operated by The Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Visiting Astronomer, Solar Division, Kitt Peak National Observatory.  相似文献   

11.
O. Engvold 《Solar physics》1970,11(2):183-197
Absorption band spectra of BH and BO have been searched for and not found in spectra of sunspots.Electronic oscillator strengths are available only for the A 1 -X 1 + system of the BH molecule. The absence of the (0,0) band of BH at 4332 Å reflects a solar abundance of boron logA B<2.5.The band spectra of BN are several orders of magnitude weaker in sunspots than those of BH and BO.Kitt Peak National Observatory Contribution No. 488.Visiting Astronomer, Solar Division, Kitt Peak National Observatory - Operated by The Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

12.
The coefficients of third degree and fifth degree polynomial representations of limb darkening are tabulated for 50 wavelengths in the interval 7404-24 018.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Summer Research Assistant at Kitt Peak National Observatory 1975.  相似文献   

13.
The line-centre-magnetogram technique has been used to measure the average velocity in magnetic elements in plages and isolated magnetic elements (including dipoles) in Ca ii 8542, Mg i 5183, Fe i 8688 and C i 9111. The velocities vary from 0.6 km s–1 downflow in the line of deepest origin to zero in the highest. The smooth curve obtained by combining these with the results of other investigators is in conformity with Giovanelli's (1977) theory of inflow in the neighborhood of the temperature minimum.This material is based upon research supported by the National Science Foundation under its contract No. AST 74-04129 with the Association of Universities for Research in Astronomy, Inc., for management, operation and maintenance of the Kitt Peak National Observatory.Visiting Astronomer, Kitt Peak National Observatory.  相似文献   

14.
Existing models of the solar atmosphere predict a limb brightening in the far infrared wavelengths. At shorter wavelengths this effect is confined to the extreme limb but at 25 it extends inward from the limb to cos = 0.3. Observations of I()/I(1.0) were made with the McMath Solar Telescope through atmospheric windows at 10.4, 17.9, 20.4, and 24.2 microns, respectively. The measurements, after having been smoothed, are compared with the theoretical predictions taking into account the diffraction pattern of the telescope. The expected brightening does not appear.Kitt Peak National Observatory Contribution No. 260. - Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Presently at Kitt Peak National Observatory, Tucson, Ariz., U.S.A.  相似文献   

15.
Spectroheliograms taken in the CN(0, 0) violet band near 3883 Å show very small scale network and cell structures with high contrast. The bandhead itself, which is a broad feature due to overlap of several CN lines, allows the diagnostic simplicity of a continuum since motions, magnetic fields, and broadening mechanisms are unimportant. We have obtained spectroheliograms in the bandhead and center-to-limb photoelectric spectra of CN(0, 0) at Kitt Peak National Observatory. From the photoelectric spectra and a detailed analysis of the formation of the CN(0, 0) spectrum we derive a best-fit one-component upper photospheric model differing from that of the HSRA and recommend a change in solar carbon abundance from the HSRA value of logA c = 8.55 to logA c = 8.25. From the calibrated spectroheliograms we consider a multi-component model to account for the observed fine structure intensity variations.Staff Member, Laboratory Astrophysics Division, National Bureau of Standards.Visiting Astronomer at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

16.
The equatorial photospheric rotation rate has been observed on 14 days in 1978–1980. The resulting rotation rate, = 14.14±0.04°/day, is 2% slower than the rate as observed for long-lived sunspots.Stationed at Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.  相似文献   

17.
The Kitt Peak multi-channel magnetograph was used to make raster scans of the super-granulation. The region scanned was carefully selected to be quiet and was located at the center of the disk. Each point in the raster was observed twice (with a time interval of 150 sec) and averaged, thereby cancelling out effects of the 5 min oscillations. Subsequent raster scans were made over a period of 4 h and averaged, further reducing short-lived, nonperiodic modes and enhancing the long-lived super-granulation.The results clearly show vertical supergranular motions. These motions consist of relatively isolated patches of downward flowing material, or downdrafts, with a speed of approximately 0.1 km/sec. These downdrafts are highly correlated with patches of magnetic field, being not only cospatial with them but also approximately linearly proportional to the field strength. The magnetic field strength of these downdrafts is in the range from 50 to 100 G. These downdrafts are also regions of increased temperature (i.e., brighter than average) at all levels observed, from the Caii K line down to the level of the continuum.The observations show no contradiction with the hypothesis that the supergranulation is a convective phenomenon, but they do indicate that the convection would be far more complicated than previously supposed. In particular, the surprisingly large field strengths and the presence of a bright network at all levels suggest that the magnetic field plays a far more active role in the supergranulation.Visiting Astronomer, Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.  相似文献   

18.
MUSICOS (for MUlti-SIte COntinuous Spectroscopy) is an international project to facilitate and organize world-wide multi-site campaigns in high resolution spectroscopy, in view of obtaining a complete time coverage of various types of variable stellar phenomena.In the framework of this project a vast spectroscopic campaign was organized in December 1992, involving 8 sites well distributed in longitude around the Earth. The observations concerned three scientific programs, among which was the study of azimuthal structures in the wind and chromosphere of the pre-Main-Sequence Herbig Ae star AB Aur.The Hei 5876 line of AB Aur, which is formed in the expanding chromosphere of this star, in the innermost parts of its wind, was monitored at a resolution of 30000, nearly continuously for about 4 days. A spectacular variability of this line was discovered, the profile changing from pure emission to a composite profile including a deep absorption component in the course of a few hours. This variability can be the signature of azimuthal structures in the wind of AB Aur.We present the data collected during the campaign, and discuss possible interpretations of the spectacular variations of the Hei 5876 line.ESA/VILSPAUniversity of British Columbia CanadaBased on observations obtained during the MUSICOS 92 MUlti-SIte COntinuous Spectroscopic campaign from the National Solar Observatory McMath/Pierce 1.5 m, University of Hawaii 2.2 m, Beijing Observatory Xinglong 2.16 m, La Palma 4.2 m William Herschel Telescope, and Observatoire de Haute-Provence 1.52 m telescopes.Presented at the Cosmic Winds and the Heliosphere Conference in Tucson, Arizona, U.S.A., October 18–22, 1993.Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.Visiting Astronomer National Solar Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.  相似文献   

19.
Observations of the Ca ii H, K, and infrared triplet lines are compared with theoretical predictions from the slab models of Heasley and Milkey (1976). While the theoretical models describe the hydrogen and helium emission spectra of quiescent prominences satisfactorily the predicted Ca ii lines are systematically too bright. The most likely reason for the discrepancy is the inapplicability of the symmetric slab prominence model for lines which become even moderately optically thick in prominences.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.Visiting scientist at Kitt Peak National Observatory.  相似文献   

20.
A study of supergranule motions confirms horizontal velocities with peak values of typically 0.36 km s–1 as observed in Fe i 8688 Å. These show no significant variation with height over the range of formation of C i 9111, Fe i 8688, and Mg i 8806, but there is a substantial reduction to about one-half of this at the level of Ca ii 8542.Near disk center, supergranule vertical velocities in Fe i 8688 have rms values ±0.01 km –1, after allowance for the residual effects of the line-of-sight component of the horizontal supergranule motions, the five-minute oscillations, granule motions, and detector drift. There is a marginally-significant association of magnetic elements, and hence of cell boundaries, with downward motions; but this requires further testing.Measurements of downward velocities 0.1 km–1 in regions of strong magnetic field when using unpolarized light are attributed to the much higher downflow inside the elements themselves and have nothing to do with supergranule motions.Visiting Astronomer, Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.  相似文献   

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