共查询到20条相似文献，搜索用时 31 毫秒
1.
F. P. Keenan 《Astrophysics and Space Science》1991,186(2):277-281
EinsteinA-coefficients for transitions inSii, calculated with the atomic structure package CIV3, are used to derive the electron density sensitive emission line ratio
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相似文献
2.
New theoretical electron-density-sensitive Fe xii emission line ratios $$R_1 = I(3s^2 3p^3 {}^4S_{3/2} - 3s3p^4 {}^4P_{5/2} )/I(3s^2 3p^3 {}^2P_{3/2} - 3s3p^4 D_{5/2} )$$ and $$R_2 = I(3s^2 3p^3 {}^2P_{3/2} - 3s3p^4 {}^2D_{5/2} )/I(3s^2 3p^3 {}^4S_{3/2} - 3s3p^2 P_{3/2} )$$ are derived using R-matrix electron impact excitation rate calculations. We have identified the Fexii \(3s^2 3p^3 {}^4S_{3/2} - 3s3p^4 {}^4P_{5/2} ,{\text{ }}3s^2 3p^3 {}^2P_{3/2} - 3s^3 3p^4 {}^2D_{5/2} ,{\text{ }}3s^2 3p^3 S_{3/2} - 3s^2 3p^3 P_{3/2} \) and \(3s^2 3p^3 {}^4S_{3/2} - 3s^2 3p^3 {}^2P_{1/2}\) transitions in an active region spectrum obtained with the Harvard S-055 spectrometer on board Skylab at wavelengths of 364.0, 382.8, 1241.7, and 1349.4 Å, respectively. Electron densities determined from the observed values of R 1 (log N e ? 11.0) and R 2(log N e ? 11.4) are significantly larger than the typical active region measurements, but are similar to those derived from some active region spectra observed with the Skylab 2082A instrument, which provides observational support for the atomic data adopted in the line ratio calculations, and also for the identification of the Fe xii transitions in the S-055 spectrum. However the observed value of R 3 = I(1349.4 Å)/I(1241.7 Å) is approximately a factor of two larger than one would expect from theory which, considering that the 1349.4 Å line lies at the edge of the S-055 wavelength coverage, may reflect errors in the instrument efficiency curve. Another possibility is that the 1349.4 Å transition is blended, probably with Si ii 1350.1 Å. 相似文献
3.
Closely spaced microphotometer tracings parallel to the dispersion of one excellent frame of a K-line time sequence have been utilized for a study of the nature of the K2v
, K2R
intensities in the case of the solar chromosphere. The frequency of occurrence of the categories of intensity ratio
are as follows:
per cent;
per cent;
per cent;
per cent;
per cent. Two types of absorbing components are postulated to explain the pattern of observed K2v
, k2R
intensity ratios. One component with minor Doppler displacements acting on the normal K232 profile, where K2V
>K2R
, produces the cases K2v
K2R
, K2v
= K2R
, K2v
<K2R
. The other component arises from dark condensations which are of size 3500 kms as seen in K2R
. They have principally large down flowing velocities in the range 5–8 km/sec and are seen on K3 spectroheliograms with sizes of about 5000 kms, within the coarse network of emission. These dark condensations give rise to the situation K2R
= 0.K2-line widths are measured for all tracings where K2v
, K2R
are measurable simultaneously. The distribution curve of these widths is extremely sharp. The K2 emission source is identified with the bright fine mottles visible on the surface. Evidence for this interpretation comes from the study of auto-correlation functions of K2 intensity variations and the spacing between the bright fine mottles from both spectrograms and spectroheliograms. The life time of the fine mottling is 200 sec.The supergranular boundaries which constitute the coarse network come in two intensity classes. A low intensity network has the fine mottles as its principal contributor to the K emission. When the network is bright, the enhancement is caused by increased K emission due to the accumulation of magnetic fields at the supergranule boundary. The K2 widths of the low intensity supergranular boundary agree with the value found for the bright mottles. Those for the brighter network are lower than this value, similar to the K2 widths as seen in the active regions.It is concluded that bright fine mottling is responsible for the relation, found by Wilson and Bappu, between K emission line widths and absolute magnitudes of the stars.The paper discusses the solar cycle equivalents that stellar chromospheres can demonstrate and indicates a possible line of approach for successful detection of cyclic activity in stellar chromospheres. 相似文献
4.
We report new properties of solar magnetic fields in a quiet region as found from their magnetic power spectra. The power spectra of network and intranetwork fields (non-network fields) are separately calculated from a Big Bear magnetogram obtained with moderately high spatial resolution of 1.5 arc sec and a high sensitivity reaching 2 Mx cm-2. The effect of seeing on the power spectrum has been corrected using Fried's (1966) Modulation Transfer Function with the seeing parameter determined in our previous analysis of the magnetogram. As a result, it is found that the two-dimensional power spectra of network and non-network fields appear in a form: (
1)
-1 and (
1)
-3.5. Here
0 0.47 Mm-1 for network fields and
0 0.69 Mm-1 for non-network fields, the latter of which corresponds to the size of mesogranulation;
1 3.0 Mm-1 for both, which is about the size of a large granule. The network field spectrum below
0 appears nearly flat, whereas that of non-network fields instead decreases towards lower wave numbers as (
)
1.3. The turnover behavior of magnetic field spectra around
1 coincides with that found for the velocity power spectrum, which may justify the kinetic approach taken in previous theoretical studies of the solar magnetic power spectra. 相似文献
5.
A new polarimeter is described which allows the simultaneous determination of the four Stokes parameters analysing the electric signal both in frequency and phase. The signal consists of two frequencies
and 2
. From the 2
component the amount and the azimuth of linearly polarized light is obtained by using a two-phase lock-in amplifier (or two separate amplifiers). From the
component the circular polarization is obtained. Instrumental and spurious effects, caused by rotating elements, are avoided. Magnetographic applications in solar physics and improvements as compared to previous magnetographs are suggested. 相似文献
6.
If fluctuations in the density are neglected, the large-scale, axisymmetric azimuthal momentum equation for the solar convection zone (SCZ) contains only the velocity correlations
and
where u are the turbulent convective velocities and the brackets denote a large-scale average. The angular velocity, , and meridional motions are expanded in Legendre polynomials and in these expansions only the two leading terms are retained (for example,
where is the polar angle). Per hemisphere, the meridional circulation is, in consequence, the superposition of two flows, characterized by one, and two cells in latitude respectively. Two equations can be derived from the azimuthal momentum equation. The first one expresses the conservation of angular momentum and essentially determines the stream function of the one-cell flow in terms of
: the convective motions feed angular momentum to the inner regions of the SCZ and in the steady state a meridional flow must be present to remove this angular momentum. The second equation contains also the integral
indicative of a transport of angular momentum towards the equator.With the help of a formalism developed earlier we evaluate, for solid body rotation, the velocity correlations
and
for several values of an arbitrary parameter, D, left unspecified by the theory. The most striking result of these calculations is the increase of
with D. Next we calculate the turbulent viscosity coefficients defined by
whereC
ro
0
and C
o
0
are the velocity correlations for solid body rotation. In these calculations it was assumed that 2 was a linear function of r. The arbitrary parameter D was chosen so that the meridional flow vanishes at the surface for the rotation laws specified below. The coefficients v
ro
i
and v
0o
i
that allow for the calculation of C
ro
and C
0o
for any specified rotation law (with the proviso that 2 be linear) are the turbulent viscosity coefficients. These coefficients comply well with intuitive expectations: v
ro
1
and –v
0o
3
are the largest in each group, and v
0o
3
is negative.The equations for the meridional flow were first solved with
0 and
2 two linear functions of r (
0
1
= – 2 × 10 –12 cm –1) and (
2
1
= – 6 × 10 12 cm –1). The corresponding angular velocity increases slightly inwards at the poles and decreases at the equator in broad agreement with heliosismic observations. The computed meridional motions are far too large ( 150m s–1). Reasonable values for the meridional motions can only be obtained if
o (and in consequence ), increase sharply with depth below the surface. The calculated meridional motion at the surface consists of a weak equatorward flow for gq < 29° and of a stronger poleward flow for > 29°.In the Sun, the Taylor-Proudman balance (the Coriolis force is balanced by the pressure gradient), must be altered to include the buoyancy force. The consequences of this modification are far reaching: is not required, now, to be constant along cylinders. Instead, the latitudinal dependence of the superadiabatic gradient is determined by the rotation law. For the above rotation laws, the corresponding latitudinal variations of the convective flux are of the order of 7% in the lower SCZ. 相似文献
7.
F. P. Keenan G. A. Warren J. G. Doyle K. A. Berrington A. E. Kingston 《Solar physics》1994,150(1-2):61-70
RecentR-matrix calculations of electron impact excitation rates in Ov are used to derive the emission line intensity ratios (in energy units) $$\begin{gathered} R_1 = I(2s2p^{ 3} P - 2p^{2 3} P)/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(761.1\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ R_2 = I(2s^{2 1} S_0 - 2s2p^{ 3} P_1 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(1218.4\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ \end{gathered} $$ and $$R_3 = I(2s2p^{ 1} P_1 - 2p^{2 1} S_0 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(774.5\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ )$$ as a function of electron temperature (T e) and density (N e). These results are presented as plots ofR 1 vsR 2, andR 1 vsR 3, which should allowboth N e andT e to be deduced for the Ov line emitting region of a plasma. Electron densities derived from the (R 1,R 2) and (R 1,R 3) diagrams in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on boardSkylab are found to be compatible, and in good agreement with values ofN e estimated from line ratios in species formed at similar electron temperatures to Ov. In addition, values ofT e determined from (R 1,R 2) and (R 1,R 3) are generally close to that expected theoretically. These results provide experimental support for the accuracy of the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation. 相似文献
8.
A recent report that energetic particles measured in the solar wind may be influenced by solar gravity-mode (
-mode) oscillations motivated the search for
-mode signatures in the Ulysses solar wind plasma data. Ulysses solar wind plasma data from 1 March 1992 through the 12 April 1996 were examined in this study for signs of possible solar oscillations. The multi-taper method for spectral analysis was used to look for significant spectral peaks in the entire four-year data set, as well as in the smaller, more heliographically homogenous data set over the solar poles. Several frequencies satisfying certain significance requirements were found in the
-mode frequency range in both data sets that also agree with the previously published findings. However, these identifications are shown to be false detections, and hence the frequencies found cannot be identified as solar
modes. 相似文献
9.
In this paper two sets of improved approximate expressions of emissivity
, absorptivity
, effective temperature Teff, and frequency of peak brightness _p of gyrosynchrotron radiation are presented respectively for the ranges from 5 to 10 and 10 to 100 of harmonic numbers s(= /_B). The expressions are designed for the range from 20° to 80° of viewing angle , and the range 2 to 7 of electron energy spectral index . They are expressed by a power-law function in which the indexes are fitted by polynomial expressions of . Their statistical errors are, respectively, 24% and 32% for
and
for
and 28% for
. Their accuracies are much better than those of linear fitting of the power-law index. 相似文献
10.
A theoretical model for3He enrichments in solar energetic particles is developed. First, current-driven, electrostatic instabilities that have frequencies
(
is the cyclotron frequency of3He) are investigated for a plasma consisting of H,4He,3He, and electrons with the density of3He much lower than those of H and4He. It is found that in many cases the oblique ion-acoustic waves can have positive growth rates at frequencies
and, at the same time, negative growth rates at
and at H. This can occur near the marginal state of the instability. The wave damping at these frequencies is caused by the cyclotron resonances of4He and H. The cyclotron damping at
is negligible, however, because the abundance of3He is very small. The H cyclotron waves can be unstable at
for a wide region of plasma parameters; the electron-to-ion temperature ratio must beT
e
/T
H
1.5. To destabilize the4He cyclotron waves with
, high4He density and high electron temperature are both required. Then,3He enrichments are studied on the basis of the theory of nonlinear magnetosonic waves, which can promptly accelerate ions. The current-driven electrostatic waves with
can enhance fluctuation velocities of3He. Thus, in the presence of these waves, magnetosonic waves can selectively accelerate3He particles to high energies. Finally, cyclotron resonances of heavy ions with the waves
or
are briefly discussed. 相似文献
11.
A model is presented to explain the observed frequency distribution of flare energies, based on independent flaring at a number of distinct topological structures (separators) within active-region magnetic fields. The model is a modification and generalization of a recent model due to Craig (2001), and reconciles that model with the observed flare waiting-time distribution, and the observed absence of a flare waiting-time versus energy relationship. The basic assumptions of the model are that flares of energy E
2 occur at separators of length
, and that the frequency of flaring at a separator is defined by the Alfvén transit time of the structure. To reproduce the observed distribution of flare energies the model requires a probability distribution P(
)
–1 of separator lengths
within active regions. This prediction of the model is in principle testable. A theoretical origin for this distribution is also discussed. 相似文献
12.
Asger G. Gasanalizade 《Astrophysics and Space Science》1992,195(2):463-466
A possible semi-annual variation of the Newtonian constant of gravitationG is established. For the aphelion and perihelion points of the Earth's orbit we find, respectively,
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