共查询到20条相似文献，搜索用时 31 毫秒
1.
Robert F. Howard 《Solar physics》1993,145(1):105-109
Sunspot group and magnetic (plage) data are examined to search for a relationship between the tilt angles of active regions and the separations of their leading and following portions. A relationship is found in the sense that larger positive tilt angles are associated with larger polarity separations. This is the direction predicted by recent theoretical work (D'Silva and Choudhuri, 1992). The explanation for this appears to be that smaller surface polarity separations lead to larger magnetic tension forces, which diminish the effect of the Coriolis force that acts to twist rising flux tubes.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
2.
We present results of an analysis of 628 high-resolution magnetograms taken daily with the NSO Vacuum Telescope on Kitt Peak from 1975 to 1991. Motions in longitude on the solar surface are determined by a two-dimensional cross-correlation analysis of consecutive day pairs. We find that the measured rotation rate of small magnetic features, i.e., excluding active regions, is in excellent agreement with the results of the previous one-dimensional analysis of the same data (Komm, Howard, and Harvey, 1993). The polynomial fits show magnetic torsional oscillations, i.e., a more rigid rotation during cycle maximum and a more differential rotation during cycle minimum, but with smaller amplitudes than the one-dimensional analysis. The full width at half maximum of the cross-correlations is almost constant over latitude which shows that the active regions are effectively excluded. The agreement between the one- and two-dimensional cross-correlation analyses shows that the two different techniques are consistent and that the large-scale motions can be divided into rotational and meridional components that are not affected by each other.Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreementOperated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement 相似文献
3.
Robert Howard 《Solar physics》1985,100(1-2):171-187
The Mount Wilson solar program has figured prominently in the field of solar physics throughout this century. This review describes the development of the instrumentation and the progress of the research at Mount Wilson from 1904 to 1984.The National Optical Astronomy Observatories are operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation. 相似文献
4.
Robert F. Howard 《Solar physics》1996,169(2):293-301
Separate Mount Wilson plage and sunspot group data sets are analyzed in this review to illustrate several interesting aspects of active region axial tilt angles. (1) The distribution of tilt angles differs between plages and sunspot groups in the sense that plages have slightly higher tilt angles, on average, than do spot groups. (2) The distributions of average plage total magnetic flux, or sunspot group area, with tilt angle show a consistent effect: those groups with tilt angles nearest the average values are larger (or have a greater total flux) on average than those farther from the average values. Moreover, the average tilt angles on which these size or flux distributions are centered differ for the two types of objects, and represent closely the actual different average tilt angles for these two features. (3) The polarity separation distances of plages and sunspot groups show a clear relationship to average tilt angles. In the case of each feature, smaller polarity separations are correlated with smaller tilt angles. (4) The dynamics of regions also show a clear relationship with region tilt angles. The spot groups with tilt angles nearest the average value (or perhaps 0-deg tilt angle) have on average a faster rotation rate than those groups with extreme tilt angles.All of these tilt-angle characteristics may be assumed to be related to the physical forces that affect the magnetic flux loop that forms the region. These aspects are discussed in this brief review within the context of our current view of the formation of active region magnetic flux at the solar surface.Dedicated to Cornelis de JagerOperated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
5.
J. C. Howard 《Solar physics》1972,24(1):32-42
Extension of the identification of singly ionized dysprosium lines in the solar chromosphere and disk has been made from a recently published laboratory analysis of the first and second spectrum.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
6.
The response function defines the response of line profiles to a depth variation of such atmospheric parameters as velocity, magnetic field and turbulence. The properties of this function are derived and compared with the so-called contribution function.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
7.
A. Keith Pierce 《Solar physics》1984,90(1):195-197
It is shown that comparing an observed Fraunhofer profile to a fitted gaussian yields more information on shape and asymmetry of the solar line than the simple bisector method.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
8.
In this paper, late M giants star counts in the Milky Way central bulge are compared with those expected from the Hubble and de Vaucouleurs surface brightness distributions.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the U.S. National Science Foundation. 相似文献
9.
The commonly used magnetograph line of Fe 5250.2 Å is found to be weakly blended by telluric water vapor. This circumstance could bias solar rotation measurements.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
10.
Edward G. Schmidt Jeffrey D. Rosendhal C. P. Jewsbury 《Astrophysics and Space Science》1974,29(2):397-414
Line strengths are presented for 15 yellow supergiants and 6 Cepheids. These line strengths are compared with those obtained
previously by other investigators.
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
11.
J. W. Harvey 《Solar physics》1973,28(1):9-13
A list of solar spectral lines having simple Zeeman triplet splitting with Landé g-factors equal to or greater than 2.5 is presented.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
12.
The existence of ring-like structures is proposed in barred spirals which are accreting mass. The cases of some well-known galaxies are discussed and an interpretation is given.Visiting astronomer at CTIO, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
13.
J. W. Harvey 《Solar physics》1973,28(1):43-47
The relative intensities of the Zeeman components of molecular spectral lines are not necessarily symmetric in a strong magnetic field. This leads to non-zero net polarization for molecular lines formed in sunspots. The effect is particularly striking for lines of the (0, 0) band of the red system of CN.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
14.
Observations are presented which suggest that away from sunspots photospheric magnetic flux is quantized. Assuming the elemental area of a magnetic region to be 1 (arc-sec)2 the elemental field strength is 525 G.Kitt Peak National Observatory Contribution No. 501.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
15.
The coefficients of several polynomial representations of the limb darkening at 62 wavelengths in the UV and visible portions of the solar spectrum obtained at the McMath Solar Telescope are presented in tabular form. Full corrections for scattered light and seeing have been included in the reductions.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
16.
J. B. Zirker 《Solar physics》1989,120(2):253-259
Non-redundant arrays offer a promising technique for producing diffraction-limited solar images. Pairs of two-dimensional non-redundant arrays yield sufficient information to recover the phases of all the spatial frequencies to which they respond. The algorithms to select and test such pairs are given and applied to a particular example.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
17.
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
18.
Robert F. Howard 《Solar physics》1993,147(1):1-11
The Mount Wilson coarse array magnetograph data set is analyzed to examine the dependence of growth and decay rates on the tilt angles of the magnetic axes of the regions. It is found that there is a relationship between these quantities which is similar to that found earlier for sunspot groups. Regions near the average tilt angle show larger average (absolute) growth and decay rates. Thepercentage growth and decay rates show minima (in absolute values) at the average tilt angles because the average areas of regions are largest near this angle. This result is similar to that derived earlier for sunspot groups. As in the case of spot groups, this suggests that, for decay, the effect results from the fact that the average tilt angle may represent the simplest subsurface configuration of the flux loop or loops that make up the region. In the case of region growth, it was suggested that the more complicated loop configuration should result in increased magnetic tension in the flux loop, and thus in a slower ascent of the loop to the surface, and thus a slower growth rate. In order to examine this further, the growth and decay rates of plage regions were examined as functions of the magnetic complexity of the regions. In the case of decay, the result was as expected from the model suggested above - that is, the more complex regions decayed more slowly. But for growing regions the effect is the opposite to that expected (more complex regions grow faster, even in terms of percentage growth), so the explanation of the tilt angle effect for growing regions proposed earlier may not be valid.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation. 相似文献
19.
The National Optical Astronomy Observatories (NOAO) proposes to build 8 m telescopes at two locations. The Northern Hemisphere location is on Mauna Kea, Hawaii, and the Southern Hemisphere location is within the existing boundary of the Cerro Tololo Inter-American Observatory. This paper describes the sites under consideration and the facilities that support the operation of each telescope, namely, the telescope enclosure, the control facility, and the recoating facility.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.Operated by the Association of Universities for Research in Astronomy Inc., under contract with the National Science Foundation. 相似文献
20.
O. J. Eggen 《Astrophysics and Space Science》1988,142(1-2):145-151
Summary Distinguishing wide binaries from contiguous members of young disk population superclusters is not possible with present definitions.
Members of old disk population groups have non-parallel space motions and the question, ‘when is a wide binary’ is more easily
approached.
Presented by H. A. Abt.
Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献