共查询到20条相似文献，搜索用时 15 毫秒
1.
We present a new method for measuring the solar magnetic meridional flow, and provide a comparison with other recent work. We have performed a least-squares fit to azimuthally averaged Mount Wilson Observatory synoptic data encompassing Carrington rotations 1722 to 1929 to produce an estimate of the solar meridional flow. A parametric fit to our results expresses the solar meridional flow as v() = 28.5 sin2.5 cos. 相似文献
2.
On the basis of more abundant data a relation logPV/logR for cepheid variables (Fernie, 1965) is constructed. A linear relation between logP V and logR for classical cepheids is found, which perhaps has a break at R=10R
. On the logR/logP diagram thes-cepheids (Efremov, 1968) show a distinct sequence. Alls-cepheids present a relative variation of the radii R/R0.075. The existence of non-s-cepheids with R/R0.075 raises a point about the evolutionary place of these stars (see Efremov, 1968). One could suppose that cepheids with logP>1.1 pulsate in the first overtone. 相似文献
3.
Spectro-polarimetric observations at 2231 nm were made of NOAA 10008 near the west solar limb on 29 June 2002 using the National Solar Observatory McMath–Pierce Telescope at Kitt Peak and the California State University Northridge – National Solar Observatory infrared camera. Scans of spectra in both Stokes I and Stokes V were collected; the intensity spectra were processed to remove strong telluric absorption lines, and the Stokes V umbral spectra were corrected for instrumental polarization. The sunspot temperature is computed using the continuum contrast and umbral temperatures down to about 3700 K are observed. A strong Tii line at 2231.0 nm is used to probe the magnetic and velocity fields in the spot umbra and penumbra. Measurements of the Tii equivalent width versus plasma temperature in the sunspot agree with model predictions. Zeeman splitting measurements of the Stokes I and Stokes V profiles show magnetic fields up to 3300 G in the umbra, and a dependence of the magnetic field on the plasma temperature similar to that which was seen using Fei 1565 nm observations of the same spot two days earlier. The umbral Doppler velocity measurements are averaged in 16 azimuthal bins, and no radial flows are revealed to a limit of ±200 m s–1. A Stokes V magnetogram shows a reversal of the line-of-sight magnetic component between the limb and disk center sides of the penumbra. Because the Tii line is weak in the penumbra, individual spectra are averaged in azimuthal bins over the entire penumbral radial extent. The averaged Stokes V spectra show a magnetic reversal as a function of sunspot azimuthal angle. The mean penumbral magnetic field as measured with the Stokes V Zeeman component splitting is 1400 G. Several weak spectral lines are observed in the sunspot and the variation of the equivalent width versus temperature for four lines is examined. If these lines are from molecules, it is possible that lines at 2230.67, 2230.77, and 2231.70 nm originate from OH, while the line at 2232.21 nm may originate from CN. 相似文献
4.
A. A. Pevtsov 《Solar physics》1992,141(1):65-73
Using observational data on 14 sunspots from the Sayan Observatory vector magnetograph, a study was made of the relationship between the sunspot magnetic field and the Evershed motions. It is shown that the central area of the solar disk is dominated by an anti-correlation of the longitudinal magnetic field B
and the line-of-sight velocity V
when a maximum of V
corresponds to the neutral line of the longitudinal field. Near the limb there usually is a coincidence of the field and velocity neutral lines. There is evidence for the possible asymmetric character of the effect with respect to the central meridian. 相似文献
5.
A magnetopause that separates two regimes of different flow, additional to the separation of a magnetic field from a field-free plasma, gives rise to the formation of asymmetric Stokes profiles. Using a simple two-layer model atmosphere, where one layer comprises a magnetic field, the other being field-free, it is shown by analytical derivation that a wide variety of Stokes V profiles can be produced, having amplitude asymmetries a in the range –a. These include two-humped V profiles, which have two lobes of equal sign. For the most simple models, the asymmetry depends on the ratio of continuum intensity to the Planck radiation intensity of the magnetic layer at the wavelength of the spectral line under consideration, and on the line depth. Two-humped profiles (|a|>1) require the temperature of the magnetic layer to surpass the temperature of the line-core forming region, implying a temperature inversion, so that the V profile is partially in emission. The confrontation of this formation scenario with properties of observed one-lobe profiles of quiet-Sun network regions is inconclusive due to insufficient spatial resolution and lack of a sufficient sample of simultaneously recorded Stokes spectral lines of varying line depths. It seems, however, to be in good agreement with the observed frequent occurrence of abnormal V profiles of the very strong Nai D
2 and D
2 spectral line. A possible observational verification for the present formation scenario of abnormal Stokes V profiles and a novel method of Stokes inversion are discussed. 相似文献
6.
V. G. Eselevich 《Solar physics》1992,137(1):179-197
In this paper, by considering an example of four Carrington rotations (1671,1672,1681, and 1682), it is shown that there generally exists an exhaustive correspondence between quasi-stationary flows of fast and slow solar wind (SW), on the one hand, and their sources on the Sun: coronal holes (CHs) and the heliospheric current sheet (HCS), on the other. It is also shown that by knowing characteristics such as the coordinate of the center of gravity of CHs on the Sun, their areas S and the positions of the neutral line (NL) and of the HCS without the NL on the Sun, it becomes possible to calculate the time of appearance and the amplitude of three points on the SW velocity profile at the Earth's orbit, namely time, t
F
,and velocity amplitude, V
F
,corresponding to the mean point of the forward front of the SW flow velocity profile, the value of V = V
m
in the central part of the flow, and angular width
+ of the flow at level V = V
F
.Calculated values agree with those observed. 相似文献
7.
Theoretical electron-temperature-sensitive Mgix emission line ratios are presented forR
I =I(443.96 )/I(368.06 ),R
2 =I(439.17 )/I(368.06 ),R
3 =I(443.37 )/I(368.06 ),R
4 =I(441.22 )/I(368.06 ), andR
5 =I(448.28 )/I(368.06 ). A comparison of these with observational data for a solar active region, obtained during a rocket flight by the Solar EUV Rocket Telescope and Spectrograph (SERTS), reveals excellent agreement between theory and observation forR
1 throughR
4, with discrepancies that average only 9%. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations, and also resolves discrepancies found previously when the theoretical results were compared with solar data from the S082A instrument on boardSkylab. However in the case ofR
5, the theoretical and observed ratios differ by almost a factor of 2. This may be due to the measured intensity of the 448.28 line being seriously affected by instrumental effects, as it lies very close to the long wavelength edge of the SERTS spectral coverage (235.46–448.76 ). 相似文献
8.
The radial dependencies of four solar wind parameters (plasma density N, velocity V, temperature T, and magnitude of the interplanetary magnetic field B) are derived from remote sensing data of the solar corona and from in situ measurements in the heliosphere (Helios-1, 2, Pioneer-10, 11, and Voyager-1, 2). Using doubly logarithmic scaling (solar wind parameter vs radial distance from the Sun) one finds two distinct intervals in the ecliptic, i.e., an exponential section within, approximately, the inner heliosphere and a linear section - up to at least 61 AU - in the outer heliosphere. 相似文献
9.
A technique is proposed for separating the rays of the streamer belt with quasi-stationary and non-stationary solar wind (SW) flows. It is shown that the lifetime of rays with a quasi-stationary SW can exceed 20 days. A new method has been developed for measuring the relative density distribution of a quasi-stationary slow SW flowing along the streamer belt's ray of increased brightness, based on the LASCO/SOHO data. It is shown that the density n for such SW flows varies with the radius R according to the relationship nR
–, where =13.3–3.9 within 4 R
0 R 6 R
0 (here R
0 is the solar radius), and decreases gradually further away. It is also shown that the V(R)-profiles in some rays of the streamer belt differ little from each other, although the value of the mass flow density, j
E, at the Earth's orbit in them can vary more than by a factor of 4. This distinguishes in a crucial respect a slow SW in the streamer belt's rays from a fast SW originating in coronal holes, for which j
Econstant and the dependences V(R) in different fast flows can differ greatly. 相似文献
10.
A list of solar spectral lines in the wavelength 4300–6700 exhibiting large Stokes V amplitudes in observed spectra of active region plages and the quiet network is presented.Visiting astronomer at National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
11.
It is shown that X-ray radiation of neutron stars with magnetic fieldsB=1011–1013 G near cyclotron resonances=s
B
(s=1,2,...) is deeply affected by such quantum effects as electron-positron vacuum polarization (significant at V=3×1028
n
e
–1
(B/B
C
4)1, whereB
C
=4.4×1013G), the quantizing character of the magnetic field (significant atV=3 x 1028
n
e
–1
(B/B
c)41 whereB
c
=4.4 x 1013G), the non-harmonic character of the Landau levels, and the quantum recoil of electrons. The latter two factors shift the resonances by the frequency –s
2
B
(B/2B
c
)sin2, being the angle between the direction of radiation propagation and the magnetic field. IfVV
0 (for 1,V
0–1=(mc
2/2T)1/2), the normal mode (NM) polarizations, as well as the absorption coefficientk
1 of the extraordinary NM in the Doppler core of the first resonance (|–| B cos ), is only slightly affected by varyingb and/orV, whereas for the ordinary NM (at 1)k
2k
1
2[b + (3 + tan2–2V)2]k
1. For sufficiently largeb and/orV the quantum effects amplify resonant absorption of the ordinary NM at
B
, with spin-flip transitions playing a major role atb1+V
2. IfVV
0, the coefficientsk
1 andk
2 in the Doppler core of the resonance are of the same order and acquire some peculiar features (shifts, intersections, etc.), with the NM polarizations depending sharply on and being strongly non-orthogonal. AtVV
0,k
2=k
1(cos2 +B/2B
C
) and the polarizations are almost linear. Near high resonances (s2), as a rule,k
1,2(1 + b)
s–1
2s–3 i.e., absorption increases withb due to replacement of the thermal energy of the transverse motion of electron,T, by the magnetic energy
B
. The above effects should be taken into account for an interpretation of observational data on X-ray pulsars (e.g., Her X-1) and other X-ray sources associated with neutron stars. 相似文献
12.
A. K. R. Anantharamaiah B. Pradeep Gothoskar C. T. J. Cornwell 《Astrophysics and Space Science》1996,243(1):77-81
We present Very Large Array observations at wavelengths of 2, 3.5, 6, and 20 cm, of angular broadening of radio sources due to the solar wind in the region 2–16 solar radii. Angular broadening is anisotropic with axial ratios in the range 2–16. Larger axial ratios are observed preferentially at smaller solar distances. Assuming that anisotropy is due to scattering blobs elongated along magnetic field lines, the distribution of position angles of the elliptically broadened images indicates that the field lines are non-radial even at the largest heliocentric distances observed here. At 5R
, the major axis scattering angle is 0.7 at =6 cm and it varies with heliocentric distance asR
–1.6. The level of turbulence, characterized by the wave structure function at a scale of 10 km along the major axis, normalized to =20 cm, has a value 20±7 at 5R
and varies with heliocentric distance asR
–3. Comprison with earlier results suggest that the level of turbulence is higher during solar maximum. Assuming a power-law spectrum of electron density fluctuations, the fitted spectral exponents have values in the range 2.8–3.4 for scales sizes between 2–35 km. The data suggests temporal fluctuations (of up to 10%) in the spectral exponent on a time scale of a few tens of minutes. The observed structure functions at different solar distances do not show any evidence for an inner scale; the upper limits are 1 km at 2R
and 4 km at 13R
. These upper limits are in conflict with earlier determinations and may suggest a reduced inner scale during solar maximum. 相似文献
13.
Previous global models of coronal magnetic fields have used a geometrical construction based on a spherical source surface because of requirements for computational speed. As a result they have had difficulty accounting for (a) the tendency of full magnetohydrodynamic (MHD) models to predict non-radial plasma flow out to r 10r
and (b) the appreciable magnitude, 3, of B
r
, (the radial component of B) consistently observed at r 1 AU. We present a new modelling technique based on a non-spherical source surface, which is taken to be an isogauss of the underlying potential field generated by currents in or below the photosphere. This modification of the source surface significantly improves the agreement between the geometrical construction and the MHD solution while retaining most of the computational ease provided by a spherical source surface. A detailed comparison between the present source-surface model and the MHD solution is made for the internal dipole case. The resulting B field agrees well in magnitude and direction with the coronal B field derived from the full MHD equations. It shows evidence of the slightly equatorward meridional plasma flow that is characteristic of the MHD solution. Moreover, the B field obtained by using our non-spherical source surface agrees well with that observed by spacecraft in the vicinity of the Earth's orbit. Applied to a solar dipole field with a moment of 1 G-r
3
, the present model predicts that B
r
at r 1 AU lies in the range of 1–2 and is remarkably insensitive to heliomagnetic latitude. Our method should be applicable also to more general (i.e., more realistic) configurations of the solar magnetic field. Isogauss surfaces for two representative solar rotations, as calculated from expansions of observed photospheric magnetic-field data, are found to show large and significant deviations from sphericity. 相似文献
14.
P. K. Manoharan 《Solar physics》1993,148(1):153-167
Interplanetary Scintillation (IPS) measurements obtained from a large number of compact radio sources (nearly 150 sources) distributed over the heliocentric distance range 15–175 solar radii (R() and heliographic latitude 75° N-75° S have been used to study the global three-dimensional density distribution of the solar wind plasma. Contours of constant electron-density fluctuations (N
e) in the heliospheric plasma obtained for both the solar minimum and maximum show a strong solar latitude dependence. During low solar activity, the equatorial density-fluctuation value decreases away from the equator towards higher latitudes and is reduced by 2.5 times at the poles; the level of turbulence is reduced by a factor of 7; the solar-wind mass flux density at the poles is 25% lower than the equatorial value. However, during high solar activity, the average distribution of density fluctuations becomes spherically symmetric. In the ecliptic, the variation of N
e with the heliocentric distance follows a power law of the formR
–2.2 and it does not show any change with solar activity. 相似文献
15.
Simultaneous observations of chromospheric (H) and photospheric (Fei 5324.19 Å) magnetograms in quiet solar regions enable us to study the spatial configuration of the magnetic field in the solar atmosphere. With the typical spatial resolution of the Huairou magnetograph, the photospheric and chromospheric magnetic structures of the quiet Sun maintain a very similar pattern. Moreover, the vertical magnetic flux is almost the same from the photosphere to the chromosphere. As an intermediate step, we analyze the formation of the working lines used by the Huairou video magnetograph of the Beijing Astronomical Observatory. The Stokes V contribution function of H and Fei 5324.19 Å are calculated. It is found that our H magnetograms provide the distribution of the chromospheric magnetic field at a height some 1000–1500 km above the photosphere. 相似文献
16.
Synoptic photoelectric observations of the coronal Fexiv and Fex emission lines at 530.3 nm and 637.4 nm, respectively, are analyzed to study the rotational behavior of the solar corona as a function of latitude, height, time and temperature between 1976 (1983 for Fex) and 2001. An earlier similar analysis of the Fexiv data at 1.15 R
over only one 11-year solar activity cycle (Sime, Fisher, and Altrock, 1989, Astrophys. J.
336, 454) found suggestions of solar-cycle variations in the differential (latitude-dependent) rotation. These results are tested over the longer epoch now available. In addition, the new Fexiv 1.15 R
results are compared with those at 1.25 R
and with results from the Fex line. I find that for long-term averages, both ions show a weakly-differential rotation period that may peak near 80° latitude and then decrease to the poles. However, this high-latitude peak may be due to sensing low-latitude streamers at higher latitudes. There is an indication that the Fexiv rotation period may increase with height between 40° and 70° latitude. There is also some indication that Fex may be rotating slower than Fexiv in the mid-latitude range. This could indicate that structures with lower temperatures rotate at a slower rate. As found in the earlier study, there is very good evidence for solar-cycle-related variation in the rotation of Fexiv. At latitudes up to about 60°, the rotation varies from essentially rigid (latitude-independent) near solar minimum to differential in the rising phase of the cycle at both 1.15 R
and 1.25 R
. At latitudes above 60°, the rotation at 1.15 R
appears to be nearly rigid in the rising phase and strongly differential near solar minimum, almost exactly out of phase with the low-latitude variation. 相似文献
17.
J. M. Fontenla 《Solar physics》1979,64(1):177-186
Intensities and profiles of the H, H, H, K, and D3 lines are measured in a solar prominence. From the profiles of these lines we estimate T = 6400 K and
t = 5.7 km s–1. We construct a simple isothermal model which explains the H intensity and profile for an assumed total particle density n
T = 3 × 1011 cm–3, and a filling factor, = 1/6.From this model we find that the source function in the H line is nearly constant through the prominence. We estimate from the model that the radiative energy loss at the center of the prominence is of the order of 107 erg s–1 g–1. 相似文献
18.
Phase dependences of circular polarization were obtained with a precision Stokes polarimeter designed and constructed at the Main Astronomical Observatory of AS Ukraine. A study was made of dielectric and metallic powders with grains of diameter 10–100 m. Metallic powders were found to produce an essential circular polarization - up to 3%, just as dielectric powders did not show circular polarization values more than 0.05% Change of circular polarization with phase angle V is greatly depended on surface structure. Loose powders give phase curves with the same sign of circular polarization everywhere and with maximum at large phase angles V > 120 . Measurements of compacted powders show curves which change the sign repeatedly and have additional maxima, including a maximum at small phase angles V < 40 . A theory was created which considers a circular polarization as a result of multiple reflections of light from particulate surface. The theory provides reasonable good fit to the experimental data. It was concluded that measurements of circular polarization can be used to find metals in surface material of cosmic bodies (especially asteroids) and to determine characteristics of surface structure, in particular, to establish presence of regolith on metal-rich bodies. 相似文献
19.
S. I. Akasofu 《Solar physics》1981,71(1):175-199
It is shown that major geomagnetic storms (¦Dst¦ > 100) tend to develop at about the time of the passage of the solar current sheet or disk at the location of the Earth, provided this passage is associated with (1) a large impulsive increase of the IMF magnitude B, (2) a negative value of the IMF angle (Theta), and (3) an increasing solar wind speed. The passage occurs in association with the 27-day rotation of the warped current disk or a temporal up-down movement of the latter. The period in which ¦Dst¦/t< 0 during major storms coincides approximately with the period when the solar windmagnetosphere energy coupling function becomes 1019 erg s–1. These conclusions do not depend on the phase of the sunspot cycle.These results may be interpreted as follows: A high speed solar wind flow, originating either from flare regions or coronal holes, tends to push the solar current disk to move upward or downward for either a brief period (1 3 days) or an extended period (2 weeks). A relatively thin region of a large IMF B > 10 is often present near the moving current disk. Waves are also generated on the moving current disk, and some of them cause large changes of . A high value of is found in the region of a large IMF B near the wavy solar current disk, where has a large negative value. 相似文献
20.
Temperatures and temperature gradients for the outer corona are obtained from brightness gradients of EUV lines that were measured with the spectroheliograph on OSO-7. Brightness gradients show considerable deviations from isothermal model calculations that include collisional excitation and photoexcitation. A negative temperature gradient that gives both positive and negative ion abundance gradients appears to be able to account for the discrepancy. For 284 of Fe xv, perhaps the strongest line from the outer corona, measurements during 1972 appear to be consistent with (i) a temperature near 2.3×106K near the equator at = 1.3±0.1 solar radii from the solar center; (ii) (/T) dT/d values near -0.7 that extend from as low as = 1.2 to about = 1.8. Temperatures from strong lines of Fe xiv and Fe xvi indicate that variations of about ±0.2×106K exist along lines of sight where emission is appreciable. There appears to be some agreement between these results and temperature measurements from ion abundances in the solar wind and Doppler width of 5303. 相似文献