共查询到20条相似文献，搜索用时 31 毫秒
1.
The propagation of Alfvén waves in a simple model of a sunspot is considered. The vertical structure near the center of the umbra is modelled realistically, but the horizontal structure is not considered. The full wave equation is solved, without recourse to the WKB approximation. Only wave propagation in the vicinity of the central field line in an axially symmetric spot is examined, and it is assumed that this field line is open. By taking wave reflections into account, we find that the observations of non-thermal motions near the temperature minimum (Beckers, 1976) and in the corona (Beckers and Schneeberger, 1977) are both consistent with an upward-propagating Alfvénic energy flux density of a few times 107 erg cm–2 s–1. This flux density is too small to cool the sunspot, but it is large enough to supply the energy requirements of the transition region and corona above a sunspot. This conclusion depends on the assumptions that the observed motions are indeed Alfvénic with periods near 180 s.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
2.
E. Landi Degl'Innocenti 《Solar physics》1979,63(2):237-245
Linearly polarized intensity distributions observed in sunspots with the Marshall Space Flight Center's (MSFC) vector magnetograph are interpreted taking into account magneto-optical effects. It is shown that these effects can be responsible for the observed spiral configuration in the pattern of linear polarization, even if a purely radial, conventional sunspot model is used.On leave from: Astrophysical Observatory of Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
3.
On 11 September 1973 a peculiar prominence was observed. The prominence displayed strong ( 50km s–1) systematic motions toward and away from the observer. The unusual spectrographic appearance of the prominence might have been due to downflowing material lifted into the corona during an earlier coronal transient.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
4.
V. A. Osherovich 《Solar physics》1982,77(1-2):63-68
The structure of a stationary sunspot of circular shape is considered. Schluter-Temesvary theory, based on the similarity assumption is criticized. It is shown that this theory does not describe the observed inclination of magnetic field lines in a sunspot. A new assumption is proposed taking into account field lines which return to the photosphere. On the basis of this assumption, the main equation of the new theory is obtained and the results compare well with observations.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
5.
The similarity between the spiral topology of chromospheric fibrils and filaments observed in H near sunspots and the configuration of an axisymmetric force-free magnetic field is examined. It is suggested that some of the observed features could be interpreted in terms of the configuration of lines of force of an axisymmetric force-free chromospheric magnetic field. Implications of the results of analysis to the possible interpretations of other observed topological features near a sunspot are discussed.Visiting scientist at the High Altitude Observatory.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Sponsored by the Office of Naval Research, Contract No. N 00014-67-C-0290. 相似文献
6.
Hector Socas-Navarro Valentín Martínez Pillet David Elmore Anna Pietarila Bruce W. Lites Rafael Manso Sainz 《Solar physics》2006,235(1-2):75-86
Ellerman bombs are bright emission features observed in the wings of Hα, usually in the vicinity of magnetic concentrations.
Here we show that they can also be detected in the Ca II infrared triplet lines, which are easier to interpret and therefore
allow for more detailed diagnostics. We present full Stokes observations of the 849.8 and 854.2 nm lines acquired with the
new spectro-polarimeter SPINOR. The data show no significant linear polarization at the level of 3 × 10−4. The circular polarization profiles exhibit measureable signals with a very intricate pattern of peaks. A non-LTE analysis
of the spectral profiles emerging from these features reveals the presence of strong downflows (∼10 {km s−1}) in a hot layer between the upper photosphere and the lower chromosphere.
Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc.
(AURA), under cooperative agreement with the National Science Foundation.
The National Center for Atmospheric Research (NCAR) is sponsored by the National Science Foundation, USA. 相似文献
7.
Y. Nakagawa 《Solar physics》1973,33(1):87-101
Observations indicate modulations of the 5-min period of chromospheric oscillations in magnetically active regions of the Sun. Thee observations are examined on the basis of the diagnostic diagrams obtained previously in a theoretical study of trapped magnetoatmospheric waves, and it is shown that the observed results can be interpreted in terms of the modulations of characteristic period of the trapped magnetoatmospheric waves for various configurations and strengths of the magnetic field, such as the umbra and penumbra of a sunspot, plages, boundaries as well as inside of supergranulation cells. The physical significance of the results and the limitation of the present analysis are discussed together with the possible future direction of this type of study.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
8.
Solar rotation during the Maunder Minimum 总被引：2，自引：0，他引：2
We have measured solar surface rotation from sunspot drawings made in a.d. 1642–1644 and find probable differences from present-day rates. The 17th century sunspots rotated faster near the equator by 3 or 4%, and the differential rotation between 0 and ±20° latitude was enhanced by about a factor 3. These differences are consistent features in both spots and groups of spots and in both northern and southern hemispheres. We presume that this apparent change in surface rotation was related to the ensuing dearth of solar activity (the Maunder Minimum) which persisted until about 1715.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
9.
Philip A. Isenberg 《Solar physics》1976,50(1):49-63
The boundary between the umbra and penumbra of a sunspot is consistently observed to be very sharp, on the order of 500 km. Approximating the sunspot as a static region in a homogeneous medium with a radiative surface, temperature distributions resulting from a variety of convective motions exterior to the sunspot are calculated. The calculations suggest that, for the exterior convection to produce the observed boundary, the maximum depth of the region of inhibited convection below a sunspot umbra is on the order of 103 km. 相似文献
10.
A. I. Poland R. A. Howard M. J. Koomen D. J. Michels N. R. Sheeley Jr. 《Solar physics》1981,69(1):169-175
The Naval Research Laboratory's most recent Earth-orbiting coronagraph, called Solwind, has been observing the Sun's outer corona (2.6–10.0 R
) at 10-min intervals since March 28, 1979. These observations provide the first comprehensive view of coronal transients near the peak of a sunspot cycle. Six, well-defined transients in our quick-look data have masses ranging from 7 × 1014 g to 2 × 1016 g and outward speeds ranging from 150 km s–1 to 900 km s–1. These values are comparable to the ones that were obtained with the OSO-7 and Skylab observations during the declining phase of the last sunspot cycle. Although the amount of quick-look data is not sufficient to provide meaningful statistics, the coronal transients near sunspot maximum seem to occur with a greater frequency and a wider latitude range than the transients during the declining phase of the cycle. In both eras, there is a good, but imperfect, association between the occurrence of coronal transients and surface phenomena such as eruptive prominences and flares.On leave from the High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colo. 80307, U.S.A. Now at Goddard Space Flight Center; Greenbelt, Md. 20771, U.S.A. 相似文献
11.
The application of Unno's (1956) solution of the transfer equation for polarized radiation to the determination of thevector magnetic field is investigated. An analysis procedure utilizing non-linear least squares techniques is developed that allows one to automate the reduction of measured spectral profiles of the Stokes parameters to determine the field angles, strength as well as other parameters. The method is applied to synthetic spectra generated using a model solar atmosphere and yields results of remarkably high accuracy. The influence of additional factors upon determination of the vector field are also considered. These factors include effects of asymmetric profiles, magneto-optical effects, magnetic field gradients, unresolved field elements, scattered light, and instrumental noise.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
12.
Recurrence of solar activity: Evidence for active longitudes 总被引：1，自引：0，他引：1
Richard S. Bogart 《Solar physics》1982,76(1):155-165
The autocorrelation coefficients of the daily Wolf sunspot numbers over a period of 128 years reveal a number of interesting features of the variability of solar activity. In addition to establishing periodicities for the solar rotation, the solar activity cycle, and perhaps the Gleissberg Cycle, they suggest that active longitudes do exist, but with much greater strength and persistence in some solar cycles than in others. There is evidence for a variation in the solar rotation period, as measured by sunspot number, of as much as two days between different solar cycles.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
13.
J. Sánchez Almeida 《Solar physics》1992,137(1):1-14
Two formal solutions of the radiative transfer equation for polarized light have been proposed. One uses the Stokes parameters to describe the polarization, while the other uses the coherency matrix. It is shown in the present work that they are equivalent. Both can be used to compute response and contribution functions for the Stokes parameters and both require the solution of systems of differential equations with similar numbers of independent variables. New equations to solve the radiative transfer problem using the Stokes parameters formalism are presented. In addition, a computer code which synthesizes the Stokes profiles by means of these equations is described.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
14.
Detlev Degenhardt 《Solar physics》1993,148(1):65-84
We suppose the transport of energy in a sunspot (or pore) is described by a diffusion process. The thermal conductivities in the spot and its surroundings are assumed to be constant and isotropic, but with a reduced conductivity in the spot. The sunspot and the ambient medium are represented by semi-infinite strips of variable depth, with one common boundary. This interface is a plane inclined at an arbitrary angle with respect to the vertical in order to simulate the inclined magnetic field at the umbral/penumbral, penumbral/photospheric or pore/photospheric boundary.We show that the region with high conductivity below the interface produces a thermal disturbance in the surface layers of the umbra which manifests itself as a temperature enhancement at the umbral surface in a region near the boundary, resulting in a decreased temperature contrast across the surface. The thermal disturbance in the neighboring medium is confined to a very small region.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
15.
K. R. Nicolas G. E. Brueckner R. Tousey D. A. Tripp O. R. White R. G. Athay 《Solar physics》1977,55(2):305-319
Spectral line profiles of Si ii and Si iii are presented which were observed both at solar center and near the quiet solar limb with the Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute intensities and line profiles are derived from the photographic data. A brief discussion is given of their center-to-limb variations and of the optical thickness of the chromosphere in these lines. Nonthermal broadening velocities are found for the optically thin lines from their full width at half maximum intensity (FWHM).Also at High Altitude Observatory for part of this work.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
16.
R. G. Athay 《Solar physics》1970,12(2):175-185
Profiles are computed for Ha and two Fei lines for a differentially moving atmosphere. The results show that the profiles are asymmetric and that velocity measurements made in the Doppler cores will often lead to erroneous results when the velocity gradient is significant in the regions of the atmosphere where the core forms.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
17.
W. D. Davis 《Solar physics》1977,54(1):139-149
Measurements of electric fields in solar flares using the Stark effect exhibited by neutral helium atoms are reported. Electric field strengths as high as 700 V cm–1 are observed. Measurements of electron densities indicate that the electric fields originate from nonthermal plasma waves. Analysis of the plasma wave fields coupled with plasma density and temperature measurements indicate that the Lower Hybrid Drift instability may be present in the flaring region.The National Center for Atmospheric Research is sponsored bythe National Science Foundation. 相似文献
18.
It has been suggested that the solar differential rotation might be maintained by nearly horizontal non-spherical convective circulation called the Rossby-type waves (the wave motions characterized by the close balance of the Coriolis force and pressure gradient in horizontal motions). In this paper, such Rossby-type waves which could be excited in the upper solar convection zone are considered, and the possibility of maintenance of the solar differential rotation by such waves is examined. A numerical estimate, in terms of the rate of conversion of the kinetic energy of such wave motions into the mean rotational motion, indicates this possibility. The implications and limitations of the results are also discussed.Visiting Scientist to the High Altitude Observatory on leave of absence from the Department of Astronomy, University of Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
19.
Lorne W. Avery 《Solar physics》1970,13(2):301-311
The emission of the Ca ii K line from a spinning cylindrical spicule model is considered. In order to reproduce the observed spicule K line profiles, the model must have both radial and axial gradients in N
e and T
e. The rotating spicule model is optically thin at all heights and is hotter and more dense than a stationary model computed in a previous paper. It is proposed that the so-called Type I and Type II spicules may be structurally the same features, with different rotational velocities.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
20.
In this paper we present our results of the application of the magnetograph formula to synthetic Stokes V profiles in prominences. We investigate both the Zeeman and atomic-polarization signatures within the V profile and question why previous attempts to determine magnetic field strength, on average, were correct, even if the magnetograph formula does not apply in general.The National Center for Atmospheric Research is sponsored by the National Science FoundationSponsored by the Summer Undergraduate Program of the High Altitude Observatory 相似文献