共查询到20条相似文献，搜索用时 62 毫秒
1.
V. V. Korneev V. V. Krutov S. L. Mandelstam A. M. Urnov I. A. Zhitnik E. Ya. Golts E. Ya. Kononov Y. V. Sidelnikov 《Solar physics》1979,63(2):319-327
Results are presented of an investigation of solar flare X-ray spectra in the region 1.70–1.95 Å, obtained aboard the Intercosmos-4 satellite during the maximum of solar activity (October–November, 1970). With the use of 6 high resolution spectra in the region 1.85–1.87 Å the identification of lines due to 18 transitions of 2p 1s type, consisting of the resonance, intercombination and forbidden Fe xxv ion lines and the satellite Fe xxiv lines has been performed. With the use of the recent laboratory data the averaged wavelengths of the lines were obtained confirming the theoretically calculated ones with an accuracy about ± 0.0004 Å. A variable Doppler shift of the Fe xxv resonance lines was observed for the flare of November 16, 1970, which points to hot plasma motions with velocities up to 400 km s-1. 相似文献
2.
M. Siarkowski J. Sylwester G. Bromboszcz V. V. Korneev S. L. Mandelshtam S. N. Oparin A. M. Urnov I. A. Zhitnik S. Vasha 《Solar physics》1982,77(1-2):183-203
In this paper, the second in a series dealing with high-resolution spectra (9.14–9.33 Å) measured on board the INTERCOSMOS-16 satellite, the analysis of the physical conditions in the coronal part of the McMath 14352 active region is performed. The temperature structure of the emitting plasma is investigated on the basis of the photon fluxes measured in six selected wavelength bands involving the resonance, intercombination, and forbidden lines of the Mg xi ion and a number of satellite lines. Relative line intensities are discussed in terms of the active region plasma density. 相似文献
3.
Justin Oelgoetz Anil K. Pradhan 《Monthly notices of the Royal Astronomical Society》2001,327(4):L42-L46
It is shown that the dielectronic satellites (DES) dominate X-ray spectral formation in the 6.7-keV K α complex of Fe xxv at temperatures below that of maximum abundance in collisional ionization equilibrium T m . Owing to their extreme temperature sensitivity, the DES are excellent spectral diagnostics for in photoionized, collisional or hybrid plasmas; whereas the forbidden, intercombination and resonance lines of Fe xxv are not. A diagnostic line ratio GD ( T ) is defined including the DES and the lines, with parameters from new relativistic atomic calculations. The DES absorption resonance strengths may be obtained from differential oscillator strengths, possibly to yield the column densities. The DES contribution to highly ionized Fe should be of interest for models of redward broadening of K α features, ionized accretion discs, accretion flows and K α temporal-temperature variability in AGN. 相似文献
4.
New electron excitation rates for O vii calculated by Tayal and Kingston using the R-matrix method are used to determine theoretical emission line strengths. Values of the electron density sensitive ratio R (forbidden line to intercombination line) are found to be very similar to those deduced by other authors. However the temperature sensitive ratios G (intercombination plus forbidden lines to resonance line) are approximately 20% lower than the best previous estimates. The observed value of G for solar active regions (G = 1.0 ± 0.1) predicts an electron temperature in the range 1.1 × 106 K < T
e
< 1.8 × 106 K, which overlaps that of maximum O vii emissivity, T
M
= 1.8 × 106 K. In addition, the theoretical G versus T
e
curve is in excellent agreement with that observed for a Tokamak plasma. 相似文献
5.
R. Mewe 《Solar physics》1972,22(1):114-118
An analysis is presented of the rate coefficients occurring in the Gabriel-Jordan theory on the relative intensities of the forbidden, intercombination, and resonance lines of helium-like ions in a steady-state plasma. Simple expressions are given to show the dependence on atomic number and electron temperature. The influence of proton collisions on the excitation 23
S23
P is estimated and deviations from the theory under non-equilibrium conditions are briefly discussed. 相似文献
6.
N. M. Firstova 《Solar physics》1984,90(2):269-279
Using the Baranger-Mozer method, we explore the possibility of diagnosing the flare plasma of forbidden Hei lines, that permits the determination of the plasma oscillation frequency and noise level. Examination of the Hei lines observed in solar flare has led us to conclude that:
- the appearance of satellites of forbidden components in the flares spectrum, due to turbulent electric fields, is the most probable for Hei 3819.606 Å lines;
- the Baranger-Mozer method is more sensitive to the high-frequency component of turbulent fields than to the low-frequency ones;
- the upper limit of the turbulent oscillation level in flares is evaluated.
7.
In the solar corona the opacities of some of the prominent X-ray emission lines are on the order of 1 over typical coronal path lengths. We present and discuss a particular solution of the radiative transfer problem involving an extended, spherically symmetric coronal shell radiating isotropic, homogeneous emission in which single-scattering also takes place. Within the context of this simplified model we find that scattered radiation is an important contribution to the total emergent resonance line flux and that for the He-like family of resonance (r), intercombination (i), and forbidden (f) lines, the ratio G=(f + i)/r would decrease as a function of optical depth for disk-center emission in an extended spherically symmetric corona. 相似文献
8.
G. Bromboszcz M. Siarkowski J. Sylwester V. V. Korneev S. L. Mandelshtam S. N. Oparin A. M. Urnov I. A. Zhitnik 《Solar physics》1983,83(2):243-255
In Part IV of the series of papers about the analysis of the INTERCOSMOS 16 ADP spectra a method is developed to evaluate plasma densities from measured resonance, intercombination, and forbidden helium-like Mg xi line intensities, using plots of the so-called G and R ratios. The density is close to the low-density limit. For the active region McMath 14352 a correlation between mean plasma density and electron temperature has been found, in agreement with earlier results. In an appendix systematic differences between measured and calculated line fluxes in all bands A to F are discussed. 相似文献
9.
The variation in intensity of the solar X-ray resonance (1s
2
1
S
0 - 1s2p
1
P
1), intercombination (1s
2
1
S
0 - 1s2p
3
P
1), and forbidden (1s2
1
S
0 - 1s2s
3
P
1) lines of helium-like Ovii with 2800 MHz solar radio flux is presented for three solar rotations. A high correlation (r 0.80) exists between the intensities of all three X-ray lines and the 2800 MHz solar flux. The ratio of the forbidden to the intercombination line intensities is found to be essentially independent of long term solar activity. This ratio is used to determine upper limits on the coronal electron density and to make inferences concerning the change in density with solar activity. 相似文献
10.
Alan Hibbert Tomas Brage Janine Fleming 《Monthly notices of the Royal Astronomical Society》2002,333(4):885-893
We use both the civ3 and mchf codes to calculate oscillator strengths of allowed and intercombination lines in the 3s2 3p–3s3p2 multiplets. Valence, core–valence and some core–core correlation effects are included. The two approaches give results in excellent agreement. Core effects are particularly important for the intercombination lines, though relatively minor for allowed transitions.
We obtain a branching ratio of 1.42 with an estimated accuracy of 0.02 for the transitions, compared with an experimental value of 1.12±0.1 . The A -values of the intercombination lines are substantially different from those of previous calculations. 相似文献
We obtain a branching ratio of 1.42 with an estimated accuracy of 0.02 for the transitions, compared with an experimental value of 1.12±0.1 . The A -values of the intercombination lines are substantially different from those of previous calculations. 相似文献
11.
V.A. Ostapenko 《Astrophysics and Space Science》1997,252(1-2):335-348
Multi-channel CCD receivers are available for solar spectral research in the Astronomical Observatory of Shevchenko University of Kiev. The observational material considered here are 24 echelle spectrograms of the flare of July 15, 1981 and certain other disk and limb flares. Some temporal aspects of flare development are discussed, as well as properties of metal lines and the structure of the flare region. Disk and limb flare photometry indicate the full spatial coincidence of the emission volumes for all emission lines. No signs of altitude stratification for the lines of H and K Call, hydrogen, and other metals are detected. Metal flare emission is revealed in the cores of Fraunhofer lines, providing that a compact emission source is present in the active region and that broad wings of H and K CaII and hydrogen have formed. No broad wings are observed for metal lines. Two types of lower-intensity strips in the photospheric emission spectrum are detected; the first is the result of the lower temperature in sunspots, while the second is due to the weakening of photospheric radiation after it passes through the flare volume. No new spectral lines are observed in the spectrum of this second type of strip, which may be associated with a condensed layer of relatively cold plasma at the chromospheric level. Four components are always spatially coincident in the spectrum: (1) a compact source of higher intensity with broadened hydrogen and H and K Call line wings; (2) higher intensity in metal lines, but without broadened wings; (3) emission or absorption in helium lines; (4) a lower-intensity strip of photospheric emission due to its weakening after it passes through the flare volume. 相似文献
12.
G. A. Gurzadyan 《Astrophysics and Space Science》1977,52(1):51-104
The present paper contains an attempt to formulate a theory, based on fast electrons hypothesis, of the chromospheres of flare stars. At the same time we shall undertake a survey of observations on the emission lines of flare stars and comparisons with the theory. The general discussion in the introduction concerning the civilian right of fast electron hypothesis is followed by sections in which the following problems are tackled: the anatomy of the light curve of the flare in UV Cet-type stars or its division into two components; the sources of radiation, ionizing hydrogen and other elements, and the estimation of their power in cold dwarf stars with emission lines; conditions for the excitation of emission lines in the chromospheres of those stars; the problem of duration of luminescence of flare stars in the emission lines (observations and theory); the electron temperature and electron concentration in the chromospheres of flare stars; the problem of the luminescence of emission lines in the quiescent star; the degree of ionization and the role of inelastic collisions of the electrons in the chromosphere of flare stars; the profiles of emission lines, their broadening and intensification during the flare; the dependence of the infensity of emission lines on the flare amplitude; the nature and peculiarities of two types of the Haro flares; the impact of radiation dilution and the spectral class of the star on the equivalent width of the emission lines; the possibility of exciting the forbidden lines; the problem of generation of the emission lines of neutral and ionized helium; the possibility of the Lyman-alpha emission in flare stars, the expected parameters of such emission — the radiation power, the equivalent width and profile of the Lyman-alpha line; the possibility of the presence of the strongest (after the -line) emission line — of doublet 2800 Mgii in the spectra of flare stars, the expected value of the intensity and equivalent width of that line. 相似文献
13.
J. C. Raymond J. L. Kohl G. Noci E. Antonucci G. Tondello M. C. E. Huber L. D. Gardner P. Nicolosi S. Fineschi M. Romoli D. Spadaro O. H. W. Siegmund C. Benna A. Ciaravella S. Cranmer S. Giordano M. Karovska R. Martin J. Michels A. Modigliani G. Naletto A. Panasyuk C. Pernechele G. Poletto Peter L. Smith R. M. Suleiman L. Strachan 《Solar physics》1997,175(2):645-665
The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940–1350 Å range as well as the 470–630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a few lines, but electron collisional excitation produces most of the lines observed. Resonance, intercombination and forbidden lines are seen, and their relative line intensities are diagnostics for the ionization state and elemental abundances of the coronal gas. The elemental composition of the solar corona and solar wind vary, with the abundance of each element related to the ionization potential of its neutral atom (First Ionization Potential–FIP). It is often difficult to obtain absolute abundances, rather than abundances relative to O or Si. In this paper, we study the ionization state of the gas in two coronal streamers, and we determine the absolute abundances of oxygen and other elements in the streamers. The ionization state is close to that of a log T = 6.2 plasma. The abundances vary among, and even within, streamers. The helium abundance is lower than photospheric, and the FIP effect is present. In the core of a quiescent equatorial streamer, oxygen and other high-FIP elements are depleted by an order of magnitude compared with photospheric abundances, while they are depleted by only a factor of 3 along the edges of the streamer. The abundances along the edges of the streamer (‘legs’) resemble elemental abundances measured in the slow solar wind, supporting the identification of streamers as the source of that wind component. 相似文献
14.
Werner M. Neupert 《Solar physics》1971,18(3):474-488
Observations of solar X-ray line emission using crystal spectrometers during a large chromospheric flare have provided a list of wavelengths with a precision of 0.003 Å in first order of diffraction and correspondingly better in higher orders. In addition to the resonance, intersystem (1 1
S
0-2 3
P
1) and forbidden (1 1
S
0-2 3
S
1) transitions of ions of the Hei isoelectronic sequence, we have recorded satellite lines arising from ions in the Lii, Bei and Bi isoelectronic sequences. These satellite features are most prominent in the iron spectrum. Apparent decreases in the ratio of forbidden and intersystem line intensities of Mgxi and Sixiii during the flare are used to derive electron densities possibly as high as 1 × 1013 cm–3 in the Mgxi emitting region and 1 × 1014 cm–3 in the Sixiii region during the event. A search for satellite lines on the long-wavelength side of the Lyman-alpha line of Hi-like ions has yielded no positive identifications. 相似文献
15.
E. A. Baranovsky V. G. Lozitsky V. P. Tarashchuk 《Kinematics and Physics of Celestial Bodies》2009,25(5):254-259
The spectra of two powerful flares with approximately the same intensities in the optical region but with different spectral
features and power in other regions are studied. One of them is the unique flare which occurred on October 28, 2003, importance
X17.2/4B, ranking third in magnitude among the recorded flares. Another occurred on September 1, 1990, 3B importance. The
flares vary in the Balmer decrement. The flare of October 28, 2003, has a ratio of I(Hβ)/I(Hα) = 1.47. This is the largest value for solar flares ever observed. The flares also differ in magnitude of the D Na I lines emission: the emission of the flare of October 28, 2003, is substantially larger than that of the other flare.
The chromosphere models of the flares are computed using the observed profiles of Balmer lines and D Na I lines. The satisfactory agreement of the calculated and observed profiles is obtained for the two-component models in
which a hot component occupies 6% of the area. The hot component of the chromosphere model is characterized with the dense
condensation available in the upper layers. For the flare of October 28, 2003, this condensation is located deeper and its
substance concentration is greater than that for another flare. The Hα line intensity for the model hot component alone is approximately 30 and the continuous spectrum intensity is approximately
3% of the undisturbed level. The photosphere model is computed using the observed profiles of photosphere lines for the flare
of October 28, 2003. It is found that very broad profiles of individual sigma-components of the Fe I λ 525.0 nm line may be
only explained by the presence of magnetic fields having different directions. A great difference is detected between values
of the magnetic field strength obtained in the splitting of sigma-components and those provided by simulation. 相似文献
16.
A systematic redshift of high ionization resonance emission lines relative to the intercombination lines was found by Friedjung
et al. (1883, A & A 126, 4071983) in the UV spectra of a number of symbiotic binaries. The interpretation was not then clear. We present a study
of archival IUE and GHRS/HST spectra of the symbiotic binary CI Cyg. The shift varies during the orbital cycle which can be
understood in terms of the presence of strong circum-binary line absorption formed in an outer expanding region. 相似文献
17.
In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal
Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based
instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive
phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe XIX flare emission, with
a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX
line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles.
These flows are observed at the initial phase of the flare, and correspond to the “explosive evaporation”. The regions of
the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of
successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation
is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of
THEMIS magnetograms. 相似文献
18.
Large-scale bulk motions and hydrodynamic turbulence in the intergalactic gas that fills clusters of galaxies significantly broaden X-ray emission lines. For lines of heavy ions (primarily helium-like and hydrogen-like iron ions), the hydrodynamic broadening is appreciably larger than the thermal broadening. Since clusters of galaxies have a negligible optical depth for resonant scattering in the forbidden and intercombination lines of these ions, these lines are not additionally broadened. At the same time, they are very intense, which allows deviations of the spectrum from the Gaussian spectrum in the line wings to be investigated. The line shape proves to be an important indicator of bulk hydrodynamic processes. Doppler probing of turbulence becomes possible, because the cryogenic detectors of the X-ray observatories now ready for launch and being planned will have a high energy resolution (from 5 eV for ASTRO-E2 to 1–2 eV for Constellation-X and XEUS). We use the spectral representation of a Kolmogorov cascade in the inertial range to calculate the characteristic shapes of radiation lines. Significant deviations in the line profiles from the Gaussian profile (shape asymmetry, additional peaks, sharp breaks in the exponential tails) are expected for large-scale turbulence. The kinematic SZ effect and the X-ray line profiles carry different information about the hydrodynamic velocity distribution in clusters of galaxies and complement each other, allowing the redshift, the peculiar velocity of the cluster, and the bulk velocity dispersion to be separated. 相似文献
19.
Many excited lines and a remarkable emission in the continuum were observed in the region around the H and K lines during a strong flare. 相似文献
20.
We study the changes of the CaI λ6102.7 Å line profile and the magnetic field structure during the 1B/M2.2 while-light flare of August 12, 1981. The two brightest flare knots located in the penumbra of a sunspot with a δ configuration are investigated. The 1 ± V line profiles are analyzed. The reduction and analysis of our observations have yielded the following results. (1) The line profiles changed significantly during the flare, especially at the time of optical continuum emission observed near the flare maximum. In addition to the significant decrease in the depth, a narrow polarized emission whose Zeeman splitting corresponded to a longitudinal magnetic field strength of 3600 Gs was observed. This is much larger than the magnetic field strength in the underlying sunspot determined from the Zeeman splitting of absorption lines. (2) The largest changes of the CaI λ6102.7 Å line profile observed during the flare can lead to an underestimation of the longitudinal magnetic field strength measured with a video magnetograph by a factor of 4.5, but they cannot be responsible for the polarity reversal. (3) A sharp short-term displacement of the neutral line occurred at a time close to the flare maximum, which gave rise to a reversed-polarity magnetic field on a small area of the active region, i.e., a magnetic transient. This can be interpreted as a change in the inclination of the magnetic field lines to the line of sight during the flare. The short-term depolarization of the CaI λ6102.7 Å line emission observed at the other flare knot can also be the result of a change in the magnetic field structure. (4) These fast dynamic changes of the magnetic field lines occurred after the maximum of the impulsive flare phase and were close in time to the appearance of type II radio emission. 相似文献