共查询到20条相似文献，搜索用时 46 毫秒
1.
We have made absolute measurements at Kitt Peak of the dependence of solar rotation rate upon latitude during the period 17–20 June 1977. We observed the solar potassium line at 7699 Å using an atomic-beam resonance scattering apparatus. The measured sidereal equatorial rotation rate is 13.5±0.5 deg day–1. Our results are in agreement with those of Howard and Harvey from 1966–68. We intend to use this technique in a long-term program at Oberlin to monitor the equatorial rotation rate.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
2.
A new series of photometric observations of the H and K lines were obtained at Sacramento Peak Observatory in 1964 and 1965. In both the observations and the data reduction special attention was given to obtaining a suitable average over the solar fine structure and to defining a proper reference continuum. The results are that the central intensities of H and K are the same and equal to 4.2% of the continuum. The limb-darkening curves at the line centres are also the same for both lines. 相似文献
3.
We describe an observing program designed to obtain high spatial resolution photographic spectra of solar active region phenomena, with time resolution as short as 6 s. The Vacuum Tower Telescope and Echelle Spectrograph at Sacramento Peak Observatory are used to make observations simultaneously in H, He D3, Ca ii K, Mg b1, the CN bandhead at 3883, and the magnetically-sensitive line Fe i 6302. Images reflected from the slit jaw are exposed simultaneously in white-light and H. Observations of chromospheric heating, following a high-velocity infall along an H superpenumbral filament, are presented to illustrate the capabilities of the program.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the National Science Foundation. 相似文献
4.
Bruce W. Lites 《Solar physics》1984,90(1):1-12
The new Multi-Diode Array and the recently modified Universal Birefringent Filter were used at the Vacuum Tower Telescope at the Sacramento Peak National Observatory to measure the continuum color temperature of a sunspot penumbra between 428.4 and 667.6 nm. The results show that the color temperatures within the penumbral structures closely follow a measure of the wavelength average of the brightness temperature. These observations suggest that, if the dark penumbral filaments overlie a normal quiet photosphere, they are opaque to the radiation from below.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the National Science Foundation. 相似文献
5.
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
6.
We show that the He i 10830 A line gives reliable Doppler shift measurements in the upper chromosphere above active regions. Persistent flow patterns in active regions observed near the solar limb show features previously noted in Dopplergrams using the Civ transition region ultraviolet emission line. Unlike the Civ measurements, however, the He i absorption shows a strong correlation with the line-of-sight velocity images in certain regions of some active regions.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the United States National Science Foundation.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.Visiting Astronomers, Sacramento Peak Observatory. 相似文献
7.
Observations of quiescent prominences with the Zeiss Universal Birefringent Filter at Sacramento Peak show short-lived brightenings and velocity transients in H and D3. The larger events range in area from 25 to 170 square arc sec, have lifetimes of approximately 30 min, velocities of 30 km s–1, and total energy excesses up to 7 × 1027 ergs. These events do not disrupt the stable structure of the prominence, and are interpreted as either condensation events or low energy flares.Visiting astronomer, Sacramento Peak Observatory, operated by the Association of Universities for Research in Astronomy Inc. under contrast AST-78-17292 with the National Science Foundation.Visiting student, Sacramento Peak Observatory, operated by the Association of Universities for Research in Astronomy Inc. under contract AST-78-17292 with the National Science Foundation. 相似文献
8.
Using high-resolution pictures of the core of a unipolar sunspot observed with several cos values, we studied the center limb effect on the form of the bright umbral dots. The ratio of the apparent sizes in radial and tangential direction do not show the foreshortening effect typically observed in granular structures.On leave from University of Tabriz, Iran.Observational part of this work was done during a stay of S.K. at Sacramento Peak Observatory, U.S.A., as NRC Resident Research Associate. 相似文献
9.
J. R. Kuhn K. S. Balasubramaniam G. Kopp M. J. Penn A. J. Dombard H. Lin 《Solar physics》1994,153(1-2):143-155
Full Stokes polarimetry is obtained using the National Solar Observatory Vacuum Tower Telescope at Sacramento Peak while observing the magnetically sensitive infrared Fei line at wavelength of 1.56. A technique is described which makes use of the high magnetic resolution in this spectral range to remove instrumental polarization from observed StokesQ, U, andV line profiles.Supported under a USAF/AFOSR research initiative.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation. 相似文献
10.
Richard C. Altrock Laurence J. November George W. Simon Robert W. Milkey Simon P. Worden 《Solar physics》1975,43(1):33-37
Heights of formation of lines that do not exhibit Zeeman splitting are calculated using an LTE, partial non-LTE, and full
non-LTE approach. Non-magnetic (g=0) lines are valuable for velocity investigations in quiet-Sun magnetic field regions, and a knowledge of their formation
heights is useful for obtaining three dimensional velocity profiles in these regions.
Presently at Sacramento Peak Observatory.
Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
11.
A one-dimensional analysis of the 4571 Å line of neutral magnesium is presented. The Harvard-Smithsonian Reference Atmosphere (HSRA) and the Bilderberg Continuum Atmosphere (BCA) are used to compute the emergent line profiles at various positions on the solar disc. The resultant profiles, when compared to the observations, indicate that the HSRA electron temperature distribution is a more satisfactory representation of the solar atmosphere in the region of the temperature minimum than is the BCA. A slight modification to the HSRA is suggested which reduces the minimum temperature to 4140K and enables an even more satisfactory fit to the available data.On leave from Sacramento Peak Observatory, Air Force Cambridge Research Laboratories. 相似文献
12.
Observations of coronal holes, solar wind streams, and geomagnetic disturbances during 1973–1976 are compared in a 27-day pictorial format which shows their long-term evolution. The results leave little doubt that coronal holes are related to the high-speed streams and their associated recurrent geomagnetic disturbances. In particular, these observations strongly support the hypothesis that coronal holes are the solar origin of the high-speed streams observed in the solar wind near the ecliptic plane.Visiting Scientist, Kitt Peak National Observatory, Tucson, Arizona.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
13.
Richard C. Canfield Jay M. Pasachoff Robert E. Stencel Jacques M. Beckers 《Solar physics》1978,58(2):263-277
We have obtained spectrograms of high spatial and spectral resolution of the extreme solar limb, using the vacuum tower telescope of Sacramento Peak Observatory. We have identified emission lines in the range 3398–3526 Å, and classified them according to intensity, spatial structure (intensity variation), and profile. Some lines show spatial intensity variation; others do not. We show that this effect is related to the abundance of the element responsible for the line and the mean lower-level excitation potential of interlocked lines. We explain the effect in terms of radiative interlocking with other lines, as well as the characteristic size of the volume contributing to the mean intensity.Also Five College Astronomy Department, Amherst, Mass. 01003, U.S.A.Operated by the Association of Universities for Research in Astronomy Inc. under contract with the National Science Foundation. 相似文献
14.
We analyze spectral line profiles obtained from regions of the solar surface exhibiting either an upflow or a downflow on a spatial and temporal scale corresponding to the white-light granulation. The differences between their line bisectors are measured to quantify changes in the asymmetry of the profile resulting from granular motion. The observed bisector differences are compared with differences predicted using conflicting granular models. Models, in which the motion of large, long-lived granules decreases rapidly with increasing height in the photosphere, are compatible with the observed line profile asymmetries.NRC/NAS Resident Research Associate.Operated by the Association of Universities for Research in Astronomy, Inc. under contract AST 78-17292 with the National Science Foundation.Summer Research Assistant at Sacramento Peak Observatory 1979. 相似文献
15.
Observations of solar velocity fields made simultaneously at Mount Wilson and at Kitt Peak with the same size aperture (5 arc-sec) and same position on the disk (± 1 arc-sec) are presented. The object is to clarify whether the short-period oscillations (SPO's) previously reported (Howard, 1967), could be caused by local seeing conditions. The time of onset and general character of the SPO's are found to be well correlated for the two sites, a condition that favors a solar origin. However, because correlation in complete detail did not prove possible, some doubt must remain regarding the source of the SPO's.Kitt Peak National Observatory Contribution No. 287.Operated by The Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
16.
Phillips K.J.H. Read P.D. Gallagher P.T. Keenan F.P. Rudawy P. Rompolt B. Berlicki A. Buczylko A. Diego F. Barnsley R. Smartt R.N. Pasachoff J.M. Babcock B.A. 《Solar physics》2000,193(1-2):259-271
The Solar Eclipse Coronal Imaging System (SECIS) is an instrument designed to search for short-period modulations in the solar corona seen either during a total eclipse or with a coronagraph. The CCD cameras used in SECIS have the capability of imaging the corona at a rate of up to 70 frames a second, with the intensities in each pixel digitised in 12-bit levels. The data are captured and stored on a modified PC. With suitable optics it is thus possible to search for fast changes or short-period wave motions in the corona that will have important implications for the coronal heating mechanism. The equipment has been successfully tested using the Evans Solar Facility coronagraph at National Solar Observatory/Sacramento Peak and during the 11 August 1999 eclipse at a site in north-eastern Bulgaria. The instrument is described and preliminary results are outlined. 相似文献
17.
We searched for a variation with heliographic latitude of the solar limb effect by comparing the relative wavelengths of weak and strong Fraunhofer lines. The blue shifts associated with the limb effect appear 9%±5% larger in the polar radius vector than in an equatorial radius vector at cos = 0.5. This should perhaps be interpreted as an increase with latitude of either solar convection or of convective overshoot. Recent observations of poleward meridional flows of 30m s–1 should be corrected for this limb effect variation. This correction increases this flow velocity to 70 m s–1. A search for a similar variation in plages and in network boundaries had negative results, the variation being +1%±5% and -1%±6% respectively.Now at the Multiple Mirror Telescope Observatory, University of Arizona, Tucson, Ariz. 85721, U.S.A. The MMTO is jointly operated by the University of Arizona and the Smithsonian Institution.The Sacramento Peak Observatory is operated by the Association of Universities for Research in Astronomy, Inc. under contract AST 78-17292 with the National Science Foundation. 相似文献
18.
It is well established that both total and spectral solar irradiance are modulated by variable magnetic activity on the solar
surface. However, there is still disagreement about the contribution of individual solar features for changes in the solar
output, in particular over decadal time scales. Ionized Ca ii K line spectroheliograms are one of the major resources for these long-term trend studies, mainly because such measurements
have been available now for more than 100 years. In this paper we introduce a new Ca ii K plage and active network index time series derived from the digitization of almost 40 000 photographic solar images that
were obtained at the 60-foot solar tower, between 1915 and 1985, as a part of the monitoring program of the Mount Wilson Observatory.
We describe here the procedure we applied to calibrate the images and the properties of our new defined index, which is strongly
correlated to the average fractional area of the visible solar disk occupied by plages and active network. We show that the
long-term variation of this index is in an excellent agreement with the 11-year solar-cycle trend determined from the annual
international sunspot numbers series. Our time series agrees also very well with similar indicators derived from a different
reduction of the same data base and other Ca ii K spectroheliograms long-term synoptic programs, such as those at Kodaikanal Observatory (India), and at the National Solar
Observatory at Sacramento Peak (USA). Finally, we show that using appropriate proxies it is possible to extend this time series
up to date, making this data set one of the longest Ca ii K index series currently available. 相似文献
19.
We present, for the first time, high-spatial-resolution observations combining high-order adaptive optics (AO), frame selection, and post-facto image correction via speckle masking. The data analysis is based on observations of solar active region NOAA 10486 taken with the Dunn Solar Telescope (DST) at the Sacramento Peak Observatory (SPO) of the National Solar Observatory (NSO) on 29 October 2003. The high Strehl ratio encountered in AO corrected short-exposure images provides highly improved signal-to-noise ratios leading to a superior recovery of the object’s Fourier phases. This allows reliable detection of small-scale solar features near the diffraction limit of the telescope. Speckle masking imaging provides access to high-order wavefront aberrations, which predominantly originate at high atmospheric layers and are only partially corrected by the AO system. In addition, the observations provided qualitative measures of the image correction away from the lock point of the AO system. We further present a brief inspection of the underlying imaging theory discussing the limitations and prospects of this multi-faceted image reconstruction approach in terms of the recovery of spatial information, photometric accuracy, and spectroscopic applications.The editors apologize to the authors: due to a misunderstanding during the editorial process, the publication of this paper has been delayed. 相似文献
20.
B. Caccin A. Donati-Falchi R. Falciani L. A. Smaldone G. P. Tozzi 《Solar physics》1987,112(2):383-386
Using the method of solar bidimensional spectroscopy based on the Universal Birefringent Filter (UBF), we have determined the bidimensional maps of moments of some chromospheric lines. The observational material, referring to a quiet region on the disk center, have been acquired with the UBF of the NSO at Sacramento Peak on Aug. 27,1985. In this note we present the work in progress and the new observational aspects arising from this diagnostic method.Visiting astronomers at the National Solar Observatory/Sacramento Peak, operated by the AURA under contract with the NSF 相似文献