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1.
A few methods of estimating Fried's parameter (r
0) from specklegrams of solar features are described. Some of these methods were used to estimate r
0 for the speckle data obtained from Kodaikanal Observatory (KO), Uttar Pradesh State Observatory (UPSO) and Udaipur Solar Observatory (USO). The average value of r
0 was found to be 3 cm at USO and UPSO during our observations. At KO, values of r
0 ranging from 6 to 10 cm were estimated. 相似文献
2.
Green's Theorem is developed for the spherically-symmetric steady-state cosmic-ray equation of transport in interplanetary space. By means of it the momentum distribution functionF
o(r,p), (r=heliocentric distance,p=momentum) can be determined in a regionr
arrbwhen a source is specified throughout the region and the momentum spectrum is specified on the boundaries atr
a
andr
b
. Evaluation requires a knowledge of the Green's function which corresponds to the solution for monoenergetic particles released at heliocentric radiusr
o
, Examples of Green's functions are given for the caser
a
=0,r
b
= and derived for the cases of finiter
a
andr
b
. The diffusion coefficient is assumed of the form = o(p)r
b
. The treatment systematizes the development of all analytic solutions for steady-state solar and galactic cosmic-ray propagation and previous solutions form a subset of the present solutions. 相似文献
3.
Thirteen synoptic maps of expansion rate of the coronal magnetic field (CMF; RBR) calculated by the so-called ‘potential model’ are constructed for 13 Carrington rotations from the maximum phase of solar activity cycle 22 through the maximum phase of cycle 23. Similar 13 synoptic maps of solar wind speed (SWS) estimated by interplanetary scintillation observations are constructed for the same 13 Carrington rotations as the ones for the RBR. The correlation diagrams between the RBR and the SWS are plotted with the data of these 13 synoptic maps. It is found that the correlation is negative and high in this time period. It is further found that the linear correlation is improved if the data are classified into two groups by the magnitude of radial component of photospheric magnetic field, |Bphor|; group 1, 0.0 G ≦ |Brpho| < 17.8 G and group 2, 17.8 G ≦ |Brpho|. There exists a strong negative correlation between the RBR and the SWS for the group 1 in contrast with a weak negative correlation for the group 2. Group 1 has a double peak in the density distribution of data points in the correlation diagram; a sharp peak for high-speed solar wind and a low peak for low-speed solar wind. These two peaks are located just on the axis of maximum variance of data points in the correlation diagram. This result suggests that the solar wind consists of two major components and both the high-speed and the low-speed winds emanating from weak photospheric magnetic regions are accelerated by the same mechanism in the course of solar activity cycle. It is also pointed out that the SWS can be estimated by the RBR of group 1 with an empirical formula obtained in this paper during the entire solar activity cycle. 相似文献
4.
Results are presented from a study of various sunspot contrast parameters in broadband red (672.3 nm) Cartesian full-disk
digital images taken at the San Fernando Observatory (SFO) over eight years, 1997 – 2004, of the twenty-third sunspot cycle.
A subset of over 2700 red sunspots was analyzed and values of average and maximum sunspot contrast as well as maximum umbral
contrast were compared to various sunspot parameters. Average and maximum sunspot contrasts were found to be significantly
correlated with sunspot area (r
s=− 0.623 and r
s=− 0.714, respectively). Maximum umbral contrast was found to be significantly correlated with umbral area (r
s=− 0.535). These results are in agreement with the works of numerous other authors. No significant dependence was detected
between average contrast, maximum contrast, or maximum umbral contrast during the rising phase of the solar cycle (r
s=0.024, r
s=0.033, and r
s=0.064, respectively). During the decay phase, no significant correlation was found between average contrast or maximum contrast
and time (r
s=− 0.057 and r
s=0.009, respectively), with a weak dependence seen between maximum umbral contrast and cycle (r
s=0.102). 相似文献
5.
A general computer program has been developed to numerically integrate the Thomson scattered light from arbitrary inhomogeneous models of the solar corona. Conversion from the observer's to solar coordinates is totally general to eliminate restrictions on the lines-of-sight that may be investigated. The tangential and radial components (K
t
and K
r
),or any combination thereof, are calculated. Four separate output modes are available, corresponding to the common formats used for coronal brightness and polarization data.This program was used to investigate the major NW streamer of the 1972 eclipse. The bifurcated profile of this feature is reproduced by the projection effect of a radially expanding blade, or fan, whose longitudinal axis is twisted to follow an underlying magnetic neutral line on the solar surface. Thus a purely geometrical effect accounts for the observed intensity profile. Published brightness data for the NE streamer of the 1970 eclipse are also reinterpreted using the radially-expanding fan model. The axial density gradients of 1970 and 1972 features are found to be virtually identical from 3 to 8 R
. 相似文献
6.
The propagation time for solar protons observed during the events of January 24, February 25 and March 17, 1969 are compared with those estimated from numerical solutions of the Fokker-Planck transport equation, using values of the diffusion coefficient of the form K
r
= K
0
r
b
where r is radial distance from the Sun, K
0 is obtained from the plasma-field parameters near the Earth and b varies from - 3 to + 1. K
0 is derived either by assuming that all the magnetic fluctuation power is in small amplitude transverse waves or alternatively in discontinuous changes in ¦B¦ along the flux tube of propagation. In the first case it is found that the K
0 values calculated require either b -3, implying a very rapid wave growth with r, or the Fokker-Planck equation reduces to the situation of purely convective transport which is at variance with the experimental observations. More reasonable results are found in the second case although even here K
0 is probably underestimated. Alternative ways of deducing K
0 empirically from particle anisotropy measurements are put forward and these seem to favour the discontinuity model. 相似文献
7.
Digitized synoptic charts of photospheric magnetic fields were analyzed for the past 4 incomplete solar activity cycles (1969–2000).
The zonal structure and cyclic evolution of large-scale solar magnetic fields were investigated using the calculated values
of the radial B
r, |B
r|, meridional B
θ, |B
θ|, and azimuthal B
φ, |B
φ| components of the solar magnetic field averaged over a Carrington rotation (CR). The time–latitude diagrams of all 6 parameters
and their correlation analysis clearly reveal a zonal structure and two types of the meridional poleward drift of magnetic
fields with the characteristic times of travel from the equator to the poles equal to ∼16–18 and ∼2–3 years. A conclusion
is made that we observe two different processes of reorganization of magnetic fields in the Sun that are related to generation
of magnetic fields and their subsequent redistribution in the process of emergence from the field generation region to the
solar surface. Redistribution is supposed to be caused by some external forces (presumably, by sub-surface plasma flows in
the convection zone). 相似文献
8.
New theoretical emission line ratios for the Be-sequence ions Mgix and Sixi are presented. A comparison with observational data for two solar flares and an active region loop obtained with the Harvard EUV spectrometer and NRL XUV spectroheliograph aboard Skylab reveals that these plasmas are in ionization equilibrium at coronal temperatures. Unfortunately most of the density diagnostics are not particularly useful under solar plasma conditions, as they vary only slightly over the electron density range 108–1013cm–3. However the Sixi ratioI(3
P
e
2 -3
P
o
2)/I(3
P
o
1 –1
S
e
0) is density sensitive in the range 108 to 1010cm–3, which is representative of electron densities found in solar active regions or small flares. 相似文献
9.
Four series of coronal images have been obtained by the expedition of Abastumani Astrophysical Observatory during the August
11, 1999 total solar eclipse with the help of a photographic mirror–lens polarimeter (D = 100 mm, F = 1000 mm). Each series include three images corresponding to three positions of the polarization analyzer. The position
of the solar disk center relative to the Moon's center has been determined beforehand. In addition, the background skylight
polarization and intensity are calculated. All measurements are absolute given in units of the Sun's average surface brightness.
A new technique for separation of the F- and K-coronae is used. It was found that in the equatorial regions the model of hydrostatic distribution of the density with T = constant is not quite accurate for the August 11, 1999 corona and there is a temperature gradient in this region. For r1 = 1.3R⊙ and r2 = 1.8R⊙ we derived T1 = 1.25×106 K and T2 = 1.07×106 K, respectively. The average polarization degree in the equatorial regions changes from 10 to 40%, while in the polar regions
the maximum value reaches only 10%. The values of electron densities Ne(r) vary from 1.32×108 cm−3 (r = 1.1R⊙) to 2.0×106 cm−3 (r = 2.0R⊙). Our data are compared with previous measurements. 相似文献
10.
Berrilli F. Del Moro D. Consolini G. Pietropaolo E. Duvall T.L. Kosovichev A.G. 《Solar physics》2004,221(1):33-45
We investigate spatial dislocation ordering of the solar structures associated with supergranulation and granulation scales.
The supergranular and granular structures are automatically segmented from time-distance divergence maps and from broad-band
images, respectively. The spatial dislocation ordering analysis is accomplished by applying the statistical method of Pair
Correlation Function, g
2(r), to segmented features in the solar fields. We compare the computed g
2(r) functions obtained from both single and persistent, i.e., time-averaged, fields associated with supergranulation and granulation.
We conclude that supergranulation and granulation patterns present a different topological order both in single and persistent
fields. The analysis carried out on single fields suggests that the granulation behaves as an essentially random distribution
of soft plasma features with a very broad distribution in size, while supergranulation behaves as a random distribution of
close packed, coherent stiff features with a rather defined mean size. 相似文献
11.
Jacques M. Beckers 《Experimental Astronomy》2001,12(1):1-20
In this article I describe a site survey facility, which measures the signals of the solar equivalent of a Differential Image Motion Monitor (S-DIMM) and of a six element linear array of solar scintillometers. Combining the S-DIMM r
o andscintillometer I observations allows the determination of the fractions of the seeing in the free atmosphere and in the ground/lake layer. From the scintillometer array observations C
n
2
(h) is determined for heights corresponding to the first 500 m along the line-of-sight. With minor changes this seeing monitor can also be used for other extended objects like the Moon and planets. 相似文献
12.
Y. M. Almleakyd Y. E. Helali H. M. Basurah A. A. Malawi A. A. Goharji M. N. Esmaial 《Earth, Moon, and Planets》1996,73(2):109-115
Two methods have been used to compute and compare the perturbations in perigee distance for an artificial Earth satellite. The two methods have used different air density models. The first (Helali, 1987) used the TD model, formulated by Sehnel (1986a), which contains terms that describe all the principal changes of the thermospheric density due to solar activity, geomagnetic activity, and the height. The second method (Davis, 1963) used a model of the density which takes into account the rotation of the atmosphere, the bulging atmosphere and the height. For different values of eccentricities from 0.001 to 0.05 we computed the perturbations P
r
in the perigee distance at different heights from 200 to 350 km for both methods. The results show a good agreement for the computed values of P
r
for different values of e (0 < e 0.02) in both methods at perigee heights from 250 to 350 km. Meanwhile, for perigee heights smaller than about 250 km we found a maximum difference in P
r
amounting to 20 metres/revolution for e = 0.005 and 0.01. 相似文献
13.
For infinitesimal, homologous perturbations, stability analysis has found the solar radiative interior thermally stable. It is considered for the first time here whether stability is preserved when finite amplitude nonhomologous perturbations are present. We argue that local heated regions may develop in the solar core due to magnetic instabilities. Simple numerical estimations are derived for the timescales of the decay of these events and, when heated bubbles are generated that rise towards the surface, of their rising motion. These estimations suggest that the solar core is in a metastable state. For more detailed analysis, we developed a numerical code to solve the differential equation system. Our calculations determined the conditions of metastability and the evolution of timescales. We obtained two principal results. One of them shows that small amplitude heating events (with energy surplus Qo < 1026 ergs) contribute to subtle but long-lifetime heat waves and give the solar interior a persistently oscillating character. Interestingly, the slow decay of heat waves may make their accumulation possible and so their overlapping may contribute to the development of an intermittent, individual, local process of bubble generation, which may also be generated directly by stronger (Qo > 1026 ergs) heating events. Our second principal result is that for heated regions with ΔT/T ≥ 10−4 and radius 105–106cm, the generated bubbles may travel distances larger than their linear size. We point out to some possible observable consequences of the obtained results. 相似文献
14.
Using the broad band spectral index of 164 blazars in a low state, we studied the possible correlation between different broad band spectral index (α r.ir , α r.o , α r.x , α r.γ , α ir.o , α ir.x , α ir.γ , α o.x , α o.γ , α x.γ ). We also studied the possible correlation between different broad band spectral index of high-frequency peaked Bl Lac object (HBL), low-frequency peaked BL Lac object (LBL) and flat spectral radio quasars (FSRQs), respectively. The strong anti-correlations were found between α r.o and α o.γ , between α r.o and α x.γ in a low state for our blazar sample. For LBL and FSRQs, the strong anti-correlations were found between α r.ir and α ir.x , between α r.o and α o.x , and between α r.o and α o.γ in a low state. Based on these results, we suggested that the seed photons of the γ-ray drive from both the jet and the external accretion disk or the broad-line region, and that the subclasses of blazars seem to the different emission mechanism. 相似文献
15.
High-resolution optical spectroscopy of the V2324 Cyg variable star associated with the IR source IRAS 20572+4919 is performed for the first time. More than 200 absorption features (mostly Fe II, Ti II, Cr II, Y II, Ba II, and Y II) are identified in the wavelength interval from 4549 to 7880 Å. The spectral type and rotation velocity of the star are found to be F0 III and V sin i = 69 km/s, respectively. Neutral-hydrogen and NaI D lines have complex P Cyg-type profiles. Neither systematic trend of radial velocity Vr with line depth Ro nor temporal variability of Vr have been found. We found that the value for the average heliocentric radial velocity is Vr = ?16.8 ± 0.6 km/s. The radial velocities inferred from the cores of the absorption components of the Hβ and NaI wind lines vary from ?140 to ?225 km/s (and the expansion velocities of the corresponding layers, from about 120 to 210 km/s). The maximum expansion velocity is found for the blue component of the split Hα absorption: 450 km/s for December 12, 1995. The method of model atmospheres is used to determine the following parameters of the star: effective temperature T eff = 7500 K, surface gravity log g = 2.0, microturbulence velocity ξ t = 6.0 km/s, and metallicity, which is equal to the solar value. The main peculiarity of the chemical composition of the star is the overabundance of lithium and sodium. The results cast some doubt on the classification of V2324 Cyg as a post-AGB star. 相似文献
16.
Comet outburst activity and the structure of solar wind streams were compared on the basis of Pioneer 10, 11, Vela 3 and IMP
7, 8 measurements at the heliocentric distance r ≈ 1–6 AU. It is shown that the solar wind velocity waves which are evolving into corotating shock waves beyond the Earth
orbit may be responsible for comet outburst activity. The correlation between variations of comet outburst activity with heliocentric
distance and the behavior of the solar wind velocity waves is established. The closeness of the characteristic times for the
velocity waves and comet outburst activity (7–8 days at r = 1 AU) as well as the simultaneous growth of both the characteristic times with r are noted. The observed distribution of the comet outburst activity parameters during the 11-year cycle is also in good agreement
with the phase distributions during the 11-year cycle of variations of the coronal hole areas and the rate of change of the
sunspot area δS
p. 相似文献
17.
The scattering of radiowaves in the outer solar corona is discussed. Results are given of the decametric wave observations.
In the theoretical analysis both regular refraction and the gradients in the electron density fluctuations are considered.
The theory is in satisfactory agreement with the experimental data. From their comparison the ratio n=(l
r
/l
t
) is deduced of the correlation scales in the radial (l
r
)and transverse directions. This value is not equal to the ratio of the observed distribution dimensions. The frequency dependence
of the angular spectrum rms width is not λ2 at longer wavelengths. At small separations from the Sun, however, the rms angular size cannot serve as the only characteristic
of the spectrum, the latter being non-Gaussian.
Referred to in the paper as the Ukr. IRE. 相似文献
18.
Myron Lecar 《Celestial Mechanics and Dynamical Astronomy》1996,64(1-2):163-166
We have accumulated thousands of orbits of test particles in the Solar System from the asteroid belt to beyond the orbit of Neptune. We find that the time for an orbit to make a close encounter with a perturbing planet, T
c
,is a function of the Lyapunov time, T
ty
.The relation is log (T
c
/T
o
)= a + b log (T
ly
T
o
)where T
o
is a fiducial period which we have taken as the period of the principal perturber or the period of the asteroid. There are exceptions to this rule interior to the 2/3 resonance with Jupiter. There, at least in the restricted problem, for sufficiently small Jupiter mass, orbits may have a positive Lyapunov exponent and still be blocked from having a close approach to Jupiter by a zero velocity curve. Of more serious concern is whether the relation holds for purely secular resonances, and if it does, how to choose T
o
.This is the case of interest for the planets in the solar system. 相似文献
19.
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
20.
An attempt is made to infer the structure of the solar convection zone from observedp-mode frequencies of solar oscillations. The differential asymptotic inversion technique is used to find the sound speed in
the solar envelope. It is found that envelope models which use the Canuto-Mazzitelli (CM) formulation for calculating the
convective flux give significantly better agreement with observations than models constructed using the mixing length formalism.
This inference can be drawn from both the scaled frequency differences and the sound speed difference. The sound speed in
the CM envelope model is within 0.2% of that in the Sun except in the region withr > 0.99R
⊙. The envelope models are extended below the convection zone, to find some evidence for the gravitational settling of helium
beneath the base of the convection zone. It turns out that for models with a steep composition gradient below the convection
zone, the convection zone depth has to be increased by about 6 Mm in order to get agreement with helioseismic observations. 相似文献