共查询到20条相似文献，搜索用时 31 毫秒
1.
During the total solar eclipse of 11 June, 1983, an imaging dual-channel Fabry-Pérot interferometer was used to obtain line profiles simultaneously in the green 5303 Å [Fe xiv] and the red 6374 Å [Fe x] coronal lines at various positions in the corona. Extensive microdensitometry followed by multi-Gaussian curve-fitting analysis has resulted in the determination of coronal temperatures and velocity separations between different pockets of coronal gas in the line of sight over a large extent of the corona. Fewer high temperature zones are to be found in the corona of 1983 compared with our similar green-line measurements of the solar maximum corona of 1980. The data are consistent with a temperature maximum occurring at 1.2 R
, as found at the 1980 eclipse, but our new data are insufficient to observe farther out than this radius and so determine the position of a maximum. The velocity field in the corona at the 1983 eclipse is less structured compared with that at the 1980 eclipse and is mainly confined to the zone 20–30km s–1. 相似文献
2.
Fabry-Pérot interferometric observations of the corona were carried out. The 6374 Å line shows radial velocities between 10 and 70 km sec-1, both positive and negative. Most profiles of the 6374 Å line are not Gaussian. The widths of the lines indicate unacceptably high temperatures, and thus suggest turbulent velocities, which appear to be of the same order as the line displacement velocities. Arguments are put forward that the corona consists mainly of individual non-turbulent knots with relative velocities similar to the measured ones. 相似文献
3.
A tachometer for measuring the displacements of the center of gravity of spectral line profiles is developed. The implementation of the device, basically a Fabry-Pérot etalon, is given. The spectral shifts are determined, using the frequency of a laser as reference. 相似文献
4.
D.L. Mickey 《Solar physics》2004,220(1):21-27
I describe a method for quickly and accurately determining the plate parallelism in a tunable Fabry-Pérot interferometer. The method takes advantage of the fact that our Fabry-Pérot is installed in a spectropolarimeter: we measure profiles of solar or telluric absorption lines in three differently polarized telescope subapertures and use the residual polarization profiles to determine the plate parallelism error. An example of the error as a function of time during the observing day is also shown; it changes in a consistent way with telescope hour angle but the drift is enough to require frequent adjustment. 相似文献
5.
J. Meaburn 《Astrophysics and Space Science》1968,2(1):115-127
The reasons for applying scanning Fabry-Pérot interferometers to the study of faint but extensive gaseous nebulae are outlined. Three ways of increasing the luminosity-resolutin product of the Fabry-Pérot are then investigated. 相似文献
6.
K. P .Raju J. N. Desai T. Chandrasekhar N. M. Ashok 《Journal of Astrophysics and Astronomy》1991,12(4):311-317
The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distancer(=R/R0,R 0 is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (～ 1.4R 0). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R0, in some of the position angles. 相似文献
7.
D. P. K. Banerjee B. G. Anandarao J. N. Desai N. S. Jog P. K. Kikani R. K. Mahadkar K. S. B. Manian F. M. Pathan N. C. Shah M. Thomas 《Astrophysics and Space Science》1987,139(2):327-335
We describe here a scanning piezo-electric Fabry-Pérot spectrometer operating in the photoncounting mode whose plate spacing and parallelism are maintained by a servo-controlled system, ensuring high accuracy, for the study of emission lines from extended astronomical objects in the spectral range 4500–7000 Å. Details of the optical set-up and the Data Acquisition System (DAS) are described. Its performance at the Cassegrain focus of the 1 m telescope at Kavalur is discussed. Some line profiles on planetary nebulae studied with the above spectrometer are also presented. 相似文献
8.
A time sequence over 80 min of coronal green-line spectra was obtained with a corona- graph at the Norikura Solar Observatory. Doppler velocities, line intensities, and line widths were derived through fitting a single Gaussian to the observed line profiles. Coronal waves have been clearly detected in the Doppler velocity data. The Fourier analysis shows powers in a 1–3 mHz range, and in higher frequencies (5–7 mHz) at localized regions. The propagation speed of the waves was estimated by correlation analysis. The line intensity and line width did not show clear oscillations, but their phase relationship with the Doppler velocity indicates propagating waves rather than standing waves. The existence of Alfvén waves whose speed is 500 km s–1 or faster is possible but inconclusive, while the existence of slower waves (of the order of 100 km s–1, possibly sound waves) is evident. The energy carried by the detected sound waves is far smaller than the required heat input rate to the quiet corona. 相似文献
9.
J. Jakimiec V. V. Korneev V. V. Krutov I. A. Zhitnik S. Pŀocieniak B. Sylwester J. Sylwester 《Solar physics》1975,44(2):391-401
High resolution profiles of the Mg xii 8.42 Å line in the solar X-ray spectrum were recorded from the Intercosmos 7 satellite. The Mg xii line intensity provides a sensitive indicator of the hot plasma content (T ? 3 × 106 K) in coronal condensations and X-ray flare volumes. The ratio of the line intensity to the intensity of the adjacent continuum has been used to compute approximate thermal models of the emitting regions. For all the investigated coronal condensations the temperature distribution of plasma has been found to be a function monotonically decreasing with temperature. But for some X-ray bursts there occurred a distinct excess of the hot plasma of temperature between 6–10 × 106K. FWHM values of the Mg xii line profiles have been used to estimate ion temperature in the emitting regions. 相似文献
10.
The profiles obtained from radial-velocity observations of the Rosette Nebula with a Fabry-Pérot (F.P.) interferometer (Meaburn andSmith, 1968) had to be corrected, for the spreading action of the instrumental function, and for motion of the observer. Two current methods are compared and a method devised for fitting a sum of Gaussians to a noisy output profile. 相似文献
11.
V. A. Kovalenko 《Solar physics》1981,73(2):383-403
The energy balance of open-field regions of the corona and solar wind and the influence of the flow geometry in the corona upon the density and temperature, are analyzed. It is found that the energy flux arriving at the corona is constant for the corona's open regions with different flow geometries. For the waves heating the corona and solar wind, the dependence of the absorption coefficient on the corona's plasma density is found to be within the range of distances r=1.05–1.5R
. It is shown that the wave absorption is more dependent on electron density than the coronal emission. It is this difference that causes lower-density coronal holes to be colder than quiet regions. It is found that the additional energy flux necessary for providing energy balance of the corona and for producing solar wind is a flux of Alfvén waves, which can provide the energy needed for producing quasi-stationary high-speed solar wind streams. Theoretical models of coronal holes and the question of why the high-speed solar wind streams are precisely flowing out of coronal holes, are discussed. 相似文献
12.
The propagation and interference of Alfvén waves in magnetic regions is studied. A multilayer approximation of the standard models of the solar atmosphere is used. In each layer, there is a linear law of temperature variation and a power law of Alfvén velocity variation. The analytical solutions of a wave equation are stitched at the layer boundaries. The low-frequency Alfvén waves (P > 1 s) are able to transfer the energy from sunspots into the corona by tunneling only. The chromosphere is not a resonance filter for the Alfvén waves. The interference and resonance of Alfvén waves are found to be important to wave propagation through the magnetic coronal arches. The transmission coefficient of Alfvén waves into the corona increases sharply on the resonance frequences. To take into account the wave absorption in the corona, a method of equivalent schemes is developed. The heating of a coronal arch by Alfvén waves is discussed. 相似文献
13.
G. D. Parker 《Solar physics》1973,31(1):259-269
The coronal green line intensity is inappropriate for correlation studies of galactic cosmic ray variations. Being a non-monotonic function of coronal temperature, the green line intensity is a good index of neither coronal temperature nor solar wind speed. A more appropriate measure of coronal activity is the intensity of the electron corona. Two-dimensional observations of the K-corona trace changes in coronal morphology during the solar cycle. An index based on four years of K-coronal measurements made in Hawaii shows that activity in the lower corona is not better correlated than sunspot number with long-term modulation. Correlation analysis defines the time lag of modulation much too poorly to permit its use in estimating the size of the heliosphere. 相似文献
14.
Numerical data processing is applied to the high-resolution images-of the solar corona obtained with the 20 cm coronagraph of the Pic du Midi observatory. Two complementary methods are proposed to solve some classical difficulties usually met in the morphological analysis of the solar corona, namely the brightness gradient in the inner and medium corona, the low contrast of numerous emissive regions and the superimposition along the line of sight of different structures. The methods which are described in this paper may help to resolve the complex coronal active regions into fine structures which is now necessary to interpret all observed corona data. 相似文献
15.
A radial velocity survey has been conducted over theHii Region S101 using a pressure-scanned Fabry-Pérot polychromator/imager. The interesting velocity structure observed and the implications for this object are discussed. 相似文献
16.
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
17.
The brightness of the solar corona due to Thomson scattering depends linearly on the electron density, while the brightness due to the Balmer continuum is proportional to its square. As a consequence, information on the distribution of the electron density in the corona can be obtained by comparing the radial profiles of the surface brightness in both continua. This idea was explored for the first time in the solar eclipse of November 03, 1994, in Foz do Iguaçu, PR, Brazil. Pictures of the corona were obtained with interference filters, one centered at 477 nm (Thomson continuum) and another one at 347 nm (Balmer continuum). The second filter also transmits the Thomson continuum through its spectral window, so that the Balmer images contain Thomson contamination. This paper reports on the observational results and presents their preliminary analysis. It was found that in certain radial directions, the normalized profiles of both continua (Thomson and contaminated Balmer) coincide, but in other directions they differ significantly. The non-coincident profiles may only occur if Balmer emission becomes important in relation to the Thomson scattering. A simple calculation shows that in such cases the electron density in the inner corona must exceed the values of standard models by up to 6.1 × 104 times, maintaining however the total number of electrons along the line of sight in agreement with the prediction of standard models. It is concluded that the corona contains high electron concentration in cloudlets of subtelescopic sizes down to 106 cm. The varied behavior of the radial profiles of both continua in different radial directions, suggests that the subtelescopic structures might be related to the spatially variable topology of coronal magnetic flux tubes. 相似文献
18.
The relation between coronal green line intensity and high-speed streams of solar wind emitted by coronal holes or by loop structures of the corona is studied. As well as these exclusive regions of coronal radiative emission, other factors of solar activity have been taken into account in this relation, such as proton events, sunspot number, faculae, and solar magnetic fields.Although the investigated time period (1964–1974) is very short, because of lack of data, we attempted to define the intensity of the coronal green line as an integrated index of the solar activity which can express all the photospheric and coronal phenomena of the Sun. The contraction of the low-density coronal-hole regions and the presence of bright loops during solar maximum provide a theoretical explanation of the above-mentioned relation. 相似文献
19.
The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift, and line width simultaneously over a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of the initiation and propagation of coronal mass ejections (CMEs). Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space-weather monitoring. 相似文献
20.
Singh Jagdev Cowsik R. Raveendran A. V. Bagare S. P. Saxena A. K. Sundararaman K. Krishan Vinod Naidu Nagaraja Samson J. P. A. Gabriel F. 《Solar physics》1997,170(2):235-252
An experiment to search for short-period oscillations in the solar corona was conducted during the total solar eclipse of 1995 October 24 at Kalpi, India. The intensity in the continuum, centred around 5500 Å and with a passband having a half-width of 240 Å, was recorded at a counting rate of 20 Hz using a thermoelectric-liquid cooled photomultiplier. The power-spectrum analysis of the data reveals that most of the power is contained in 6 frequencies below 0.2 Hz. A least-square analysis gives the periods of the 6 frequency components to be 56.5, 19.5, 13.5, 8.0, 6.1, and 5.3 s. These oscillations are found to be sinusoidal, and their amplitudes are found to lie in the rangeinebreak 0.2–1.3% of the coronal brightness. Assuming these oscillations to be fast magnetosonic modes, the calculations indicate the availability of enough flux for the heating of the active regions in the solar corona. 相似文献