共查询到20条相似文献，搜索用时 250 毫秒
1.
R. G. Giovanelli 《Solar physics》1978,59(2):293-311
The cooling effect of emission in the spectral lines, which dominates over continuous emission in the chromosphere and becomes important first around the temperature minimum, modifies greatly the radiative relaxation timet
r in the solar atmosphere. This rises from low photospheric values to a maximum of 8 min just aboveT
min, falls in the low chromosphere to 1.5 min because of line emission, but rises again to 6 min atT 7000–8400 K in the chromosphere where hydrogen ionization increases the specific heat. 相似文献
2.
Numerical experiments of fictitious small bodies with initial eccentricities e=0.1 have been performed in the overlapping region of the 3/1 mean motion resonance and of thev
6 secular resonance 2.48a2.52AU for different values of the initial inclination 16°i20°. An analysis for thev
6 secular resonance shows that the topology is different from the one found outside the overlapping region: the critical argument for thev
6 resonance in the overlapping region rotates in opposite direction as compared to the purev
6 region. In the 3/1 resonance region the secular resonancev
5 is dominant, and some secondary secular resonances asv
6 –v
16 andv
5 +v
6 are present. 相似文献
3.
Slitless spectrograms obtained during the eclipse of 10 June 1972 have been analyzed to determine the height distribution of the D3 He line intensity.For undisturbed regions the maximum of D3 line intensity is confirmed to exist at about 1700km above the limb. Besides the above mentioned maximum, in plages a considerable intensity may be observed at low heights (h < 1000 km).An analysis of these observations for h > 1000 km has been carried out within the low temperature mechanism of triplet helium emission taking into account the helium ionization by XUV radiation. The density dependence of the 23
S level population at different XUV flux values has been calculated. Our observations give N
e 2 × 1010 cm–3 in the chromosphere at h = 2000 km. The probable coincidence of the H and He emission small filaments in the middle chromosphere is discussed. 相似文献
4.
E.A. Perdios 《Astrophysics and Space Science》2001,278(4):405-407
The known intervals of possible stability, on the mgr-axis, of basicfamilies of 3D periodic orbits in the restricted three-body problem areextended into -A1 regions for oblate larger primary, A
1 beingthe oblateness coefficient. Eight regions, corresponding to the basicstable bifurcation orbits l1v, l1v, l2v, l3v, m1v, m1v,m2v, i1v are determined and related branching 3D periodic orbits arecomputed systematically and tested for stability. The regions for l1v,m1v and m2v survive the test emerging as the regions allowing thesimplest types of stable low inclination 3D motion. For l1v, l2v,l3v, m1v and m2v oblateness seems to have a stabilising effect,while stability of i1v survives only for a very small range of A
1values. 相似文献
5.
Cyclotron microwave emission from magnetic stars is considered, assuming that they have coronae with the temperatureT107 K and the emission measureEM1054 cm–3. It has been shown that the cyclotron radiation from a star with a dipole magnetic field has a specific spectrum with a maximum in the frequency rangesv
o/2 >v >sv
o/2 (s being the number of cyclotron harmonic, andv
o the gyrofrequency corresponding to the polar magnetic field) and radiation flux decreasing towards lower frequencies asv
4/3. The frequency of the spectrum maximum depends on the angle between the line-of-sight and the magnetic axis of the star. The observed radiation from a rotating magnetic star can be modulated with a modulation depth of about 0.2 at frequencies near maximum. The radiation is partially circularly-polarized in the sense of an extraordinary mode. The degree of polarization is almost constant at frequenciesv >sv
o/2 and increases with frequency atv >sv
o/2. The estimation of cyclotron radio fluxes of the nearest magnetic stars shows that they are observable in microwaves by means of modern radio astronomy. 相似文献
6.
P. G. Kazantzis 《Astrophysics and Space Science》1979,65(2):493-513
New families of three-dimensional double-symmetric periodic orbits are determined numerically in the Sun-Jupiter case of the restricted three-body problem. These families bifurcate from the vertical-critical orbits (
v
= –1,c
v
),c
v=0) of the basic plane familiesi,g
1,g
2,h,a,m andl. Further the numerical procedure employed in the determination of these families has been described and interesting results have been pointed out. Also, computer plots of the orbits of these families have been shown in conical projections. 相似文献
7.
The intervals of possible stability, on the -axis, of the basic families of three-dimensional periodie motions of the restricted three-body problem (determined in an earlier paper) are extended into regions of the -m
3 parameter space of the general three-body problem. Sample three-dimensional periodic motions corresponding to these regions are computed and tested for stability. Six regions, corresponding to the vertical-critical orbitsl1v, m1v,m2v, andilv, survive this preliminary stability test-therefore, emerging as the mass parameters regions allowing the simplest types of stable low inclination three-dimensional motion of three massive bodies. 相似文献
8.
R. Muller 《Solar physics》1975,45(1):105-114
High resolution pictures (about 0.3) of photospheric faculae near the solar limb have been obtained with the Pic du Midi 50 cm refractor; their granular structure then clearly appears. The microphotometric study of these facular granules shows that the ratio of their intensity to the photospheric intensity, I
f/I
ph (cos) reaches a maximum near cos = 0.3 and then decreases towards the limb. The values of this ratio have been corrected with a most likely spread function. Then a temperature model of a facular granule is obtained: with respect to the neighbouring photosphere, this granule appears as a photospheric hot cloud which does not extend high in the solar atmosphere (thickness 100 km above 5000 = 1). The temperature excess is 750K at maximum. This hot region is located over a layer which is cooler than the normal photosphere at the same level. Another hot region might extend above the photospheric hot cloud, possibly up to the chromosphere. This photospheric facula model which is confined to the lower photosphere seems to indicate that this phenomenon is different from the photospheric network which is visible up to the lower chromosphere. 相似文献
9.
The structure of stars more massive than about 1.2M
is characterized by a convective core. We have studied the evolution with age and mass of acoustic frequencies if high radial ordern and low degree for models of stars of 1, 1.5 and 2M
. Using a polynomial approximation for the frequency, the p-mode spectrum can be characterized by derived global asteroseimic coefficients, i.e. the mean separationv
0v
n,
–v
n,–1,
and the small frequency separationv
0,2v
n,=0
–v
n,–1,=2
. The diagram(v
0,(v
0,2/v
0
plotted along the evolutionary tracks would help to separate the effects of age and mass. We study of sensitivity of these coefficients and other observable quantities, like the radius and luminosity, the stellar parameters in the vicinity of 1M
and 2M
; this sensitivity substantially depends on the stellar mass and must be taken into account for asteroseismic calibration of stellar clusters. Considering finally some rapid variations of the internal structure, we show that the second frequency difference2
v=v
n,
–2v
n,–1,
+v
n,–2,
exhibits and oscillatory behaviour well related to the rapid variation of the adiabatic exponent in the HeII ionization zone.A more complete discussion is given in Audard N, Provost J, Seismological properties of intermediate-mass stars,A&A, 1993, in press. 相似文献
10.
P. G. Kazantzis 《Astrophysics and Space Science》1979,61(2):357-367
Two new families of three-dimensional simple-symmetric periodic orbits are determined numerically in the Sun-Jupiter case of the restricted three-body problem. These families emanate from the vertical-critical orbits (v = 1,c
v
= 0)of the familiesi andl of plane symmetric simpleperiodic orbits direct around the Sun and the Sun-Jupiter respectively. Further, the numerical technique employed in the determination of these families has been described and interesting results have been pointed out. Also, computer plots of the orbits of these families have been shown in conical projections. 相似文献
11.
The muon neutrino-antineutrino flux ratios, viz.,v
/v
generated from the decays of charged pions and kaons in atmosphere have been derived from the latest primary spectrum and the CERN ISRpp-collision data modified forp-nucleus interactions. The dynamical method of Allkoferet al. (1978) has been used in the present investigation. The estimated result forv
/v
yields 1.39 and 1.70 asE0 and , respectively. The neutrino fluxes from pion- and kaon-decay spectra have been calculated. Attention has been paid on prompt neutrino spectrum calculation from the decays ofD mesons. A rough estimate on the prompt muon spectrum has been given. The calculated results have been compared with the previous available results. 相似文献
12.
Hong-Nan Zhou 《Astrophysics and Space Science》1988,141(2):199-206
The contact binary system CC Com (=12h09m33s.8, =+22°4339, (1950);V
max=11.31, (B-V)max=1.24) is a W UMa-type system with the shortest known period. The photometric solution of CC Com is presented using the Wilson and Devinney method. The results show that the CC Com belongs to the late-type eclipsing binary with the spectral type K5V and K6V, low temperatureT
1=4300 K,T
2=4265 K, the mass ratioq=0.5873±0.0021, and the inclinationi=87°.719±1°.44. The best regions of the gravity darkening exponents , the bolomotric albedov, and the limb-darkening coefficients are tested. It is found that 0.1250.065, 0.1v0.5, =0.5 are better regions for CC Com. The third body ofl
3 is not found to be significant. The results are combined with the spectroscopic results of Rucinski to provide an estimate of the absolute parameters. 相似文献
13.
Chemical composition anomalies of the corona and solar wind (FIP effect) have their origins in the chromosphere. We study the influence of the possible stratification of abundances in the chromosphere on the shape of corresponding strong Fraunhofer line profiles. A rough estimate is made of this influence for some variants of the variation in elemental abundance a
el(m) (m being the column mass). Calculations are made for the K and 8542Å Caii lines in two semi-empirical models of the chromosphere above sunspot umbra. In practice it is difficult to realize a direct search of the FIP effect in the chromosphere for lack of self-consistent theoretical models of the chromosphere required to match observations to them. An attempt is therefore proposed to find indirect signatures of the effect using a statistically significant sample of spectra for different objects, say, sunspots with a different magnetic structure and a different age. 相似文献
14.
Mitsugu Makita 《Solar physics》1972,24(1):59-71
Direct images of the Sun were photographed in continuum emission centered at 6900 Å by the jumping film method near the second contact of the Mexico eclipse on 7 March 1970. The band width was 150 Å defined by a combination of a sharp cut filter and KODAK IV F film. The intensity distribution of the solar outer layers obtained shows a steep decrease by a factor of 0.9 in logarithmic units around 2500 km. This is interpreted as the boundary of the chromosphere and corona. Spicules observed at 3500 km are explained by log n
e
= 11.25 and T
e
6000 K. Discussions are made in relation to the other observations and some chromosphere models. 相似文献
15.
Tadashi Hirayama 《Solar physics》1971,19(2):384-400
The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of Hei 3888.65 to H8 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.A new schematic model of the chromosphere is presented where spicules have no hot region of emitting neutral helium lines. Here it is suggested that the kinetic temperature of spicules, 6000 8000 K, would be primarily determined by the radiation temperature of the corona and the transition region beyond the Lyman continuum of hydrogen which happens to be around those temperatures. 相似文献
16.
K. Katopodis 《Astrophysics and Space Science》1986,125(1):149-155
In this paper we extend the computation of four families of vertical critical periodic orbitsb
1v
,b
2v
,c
1v
,c
2v
, found in part I (Ichtiaroglouet al., 1980), for >0.5. The planar stability of the periodic orbits is also examined. 相似文献
17.
J.- P. Wülser 《Solar physics》1988,114(1):115-126
H line profile observations of solar flares with high temporal resolution are an important tool for the analysis of the energy transport mechanism from the site of the flare energy release to the chromosphere. A specially designed instrument (imaging spectrograph) allows two-dimensional imaging of an active region simultaneously in 15 spectral channels along the H line profile with a temporal resolution of 5.4 s. Two flares have been observed in November 1982. The first one shows H signatures which one would typically expect in the case of explosive chromospheric evaporation produced by massive injection of non-thermal electrons. The observations of the other flare indicate that the heating of the upper chromosphere is dominated by thermal conduction, although during the impulsive hard X-ray burst there are also signatures of heating by non-thermal electrons. 相似文献
18.
Calculations are made for the center-limb variations of the K2 and K3 components of the solar Ca ii K line using an optically thick model of the chromosphere. The center-limb variations are shown to require an increase of Doppler width with height in the chromosphere and to depend critically upon the location of the point where
D has increased by a factor e. Good agreement with observations is found when, and only when, the increase in
D occurs nearly simultaneously with the increase in chromospheric temperature. 相似文献
19.
The location and the stability of the libration points in the restricted problem have been studied when small perturbation and are given to the Coriolis and the centrifugal forces respectively. It is seen that the pointsL
4 andL
5 form nearly equilateral triangles with the primaries and the pointsL
1,L
2,L
3 remain collinear. It is further observed that for the pointsL
4 andL
5, the range of stability increases or decreases depending upon whether the point (, ) lies in one or the other of the two parts in which the (, ) plane is divided by the line 36-19=0 and the stability of the collinear points is not influenced by the perturbations and they remain unstable. 相似文献
20.
Satoshi Hinata 《Solar physics》1982,80(1):173-183
Current dissipation models of coronal loop heating are studied. Turbulent current dissipation is shown to lead to a time dependent process because of an enormous mass motion induced in the current layer. A stationary heating process involves only ohmic heating, which requires a large current layer. To insure MHD stability, the loop must be composed of many elements with the oppositely directed currents. A stationary current dissipation process induces the plasma motion across the magnetic field into the loop and down the loop with the speeds v
104 cm s–1 and v
104 cm s–1, respectively. The pressure of the loop is also estimated to be proportional to the current density: p/J=6.3 × 10-8dyn/statamp. 相似文献