共查询到20条相似文献，搜索用时 15 毫秒
1.
Airborne eclipse observations of the [Six] 1430.5 nm coronal emission line are reviewed, and new ground-based out-of-eclipse coronagraph observations obtained at NSO/Sacramento
Peak are reported. We find that the [Six] 1430.5 nm coronal emission line brightness is less than 8 × 10−6
B⊙ in small active region corona which showed [Fexiii] 1074.7 nm emission (corrected for sky background) of about 20 × 10−6
B⊙.
Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National
Science Foundation. 相似文献
2.
The absolute magnitudeM
v
of the hydrogen deficient binary υ Sgr has been estimated as -4.8 ± 1.0 from the distribution of the interstellar reddening,
polarization and interstellar lines of the surrounding stars. From the ANS observations obtained at the time of the secondary
eclipse, it appears that the hotter secondary is surrounded by a disc with colours of a B8-B9 star. The λ 1550 CIv absorption
line arising in the stellar wind does not show any change in strength during the secondary minimum. The upper limit to the
mass-loss rate from the high temperature wind is estimated as ≤ 5 × 10-7 M⊙ yr-1 from the 2 cm and 6 cm radio observations.
Based on observations obtained with the Astronomical Netherlands Satellite and VLA. The National Radio Astronomy Observatory’s
Very Large Array at Socorro, New Mexico is operated by Associated Universities Inc. under contract with the National Science
Foundation. 相似文献
3.
David H. Bruning 《Solar physics》1981,71(2):233-236
The center to limb variation of solar spectral line positions, or limb effect, has been measured for the two neutral iron lines at 5250.2 Å and 5576.1 Å. Both limb effect curves show a disk-center reversal of 40–60 ms–1 and the 5576 data also exhibit a possible second reversal at the limb. The limb effect curves are best described by polynomial expressions rather than by traditional power law expressions.Visiting Student, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
4.
We study the covariance of longitudinal and latitudinal motions of small magnetic features after subtracting long-term averages
of differential rotation and meridional flow. The covariance is generally interpreted as Reynolds stress and linked to the
equatorward transport of angular momentum. Using high-resolution magnetograms taken daily with the NSO Vacuum Telescope on
Kitt Peak, we determine large-scale motions by a two-dimensional crosscorrelation analysis of pairs of consecutive daily observations
from which active regions are excluded, i.e., we analyze the motions of small magnetic features. In the present work, we focus
on 107 day pairs obtained during the year 1988 and on 472 day pairs taken in selected intervals from 1978 to 1990. We find
that all covariance values are very small (below 250 m2 s−2), which is about one to two orders of magnitude smaller than the values from sunspot measurements derived by other authors.
At active region latitudes, the masking process increases the noise, which increases the chance that the covariances at these
latitudes are not significantly different from zero. We find that the results depend strongly on the temporal averaging involved.
Daily unaveraged crosscorrelations lead to no apparent correlation between the residual velocities, while in the monthly averages
of the 1988 data, we find a covariance of −37 ± 15 m2 s−2 at 45° with a linear correlation of −0.59, which is significantly different from zero and has the right sign for an equatorial
transport of angular momentum. When we average over longer time periods, the covariance values decrease again. The annual
averages of the 1978–1990 data show both no significant covariances and the smallest errors. These small covariances imply
that the motions of small magnetic features do not reflect the transport of angular momentum via the mechanism of Reynolds
stress.
Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National
Science Foundation. 相似文献
5.
G. Beskin V. Debur V. Plokhotnichenko S. Karpov A. Biryukov L. Chmyreva A. Pozanenko K. Hurley 《Astrophysics and Space Science》2007,308(1-4):477-479
The region of SGR 1806-20 localization was observed during its gamma-ray activity in 2001. The observations have been performed
on the 6-meter telescope of the Special Astrophysical Observatory, using the Panoramic Photometer-Polarimeter (PPP). The search
for variability was performed on the 10−6–10 s time scale, and its results were compared to the properties of corresponding X-ray flares.
This work has been supported by the Russian Foundation for Basic Research (grant No 04-02-17555), Russian Academy of Sciences
(program “Evolution of Stars and Galaxies”), and by the Russian Science Support Foundation. The authors would also like to
thank the anonymous referee for his/her valuable comments. 相似文献
6.
Simultaneous observations obtained with the HAO/SPO coronal emission-line polarimeter and the new SPO emission-line coronagraph are compared. The polarimeter data are measured in the Fexiii (10747 Å) line and the coronagraph observations are recorded in the Fexiv (5303 Å) line. The polarimeter field-of-view is relatively coarse compared with the resolution limit of the coronagraph. Therefore, the observed coronal polarization cannot be related directly to the detailed loop structures that characterize the localized coronal distribution, but it is found that large-scale emission features have corresponding polarization signatures. Since the measured linear polarization vectors describe the projected magnetic field direction, as shown theoretically, it follows that the form of the large-scale coronal distribution describes corresponding magnetic field structures. Measured polarization values are consistent with those predicted theoretically. Interpretation of these data to obtain corresponding magnetic field directions suggests that the value usually accepted for iron abundance in the corona might be too large.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc. under contract AST 78-17292 with the National Science Foundation. 相似文献
7.
A preliminary discussion is presented of measurements of the polarization of the He i D3 multiplet in a quiescent prominence, observed with a wavelength-scanning Stokes polarimeter. For a series of 43 observations in the same prominence, the linear polarization of the major component of D3 lies primarily in the range 1 to 2% and of the wing component, the range 2 to 5%; the polarization vector angle lies primarily in the range 10–25° for the major component, and 25–35° for the other component. From a more limited data set, the polarization of both components is found to first increase as a function of height in the prominence, and then to decrease; the polarization angles of the major component vary in a random-like way with height, while the wing component shows a systematic change. The amount of polarization and the angle of polarization are governed by the Hanle effect. The collective effect of the group of lines at the peak of D3 evidently has a different sensitivity to the Hanle effect than does the wing component, thus yielding at least four independent measurements - two polarizations and two angles. With some redundancy, the vector magnetic field can then be established using the detailed theory of the Hanle effect. Since the wing component of D3 is a simple triplet, an initial estimate of the magnetic field strength and its horizontal orientation, 0, relative to the line of sight, is simply obtained. Examples of such calculations are presented.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc. under contract AST 78-17292 with the National Science Foundation. 相似文献
8.
Sequences of the oscillations of solar lines up to 2 hours 20 min long have been recorded at the same point on the sun. The power spectra show several peaks separated by 0.85 × 10–3 cps on average from each other. A sharp main peak at 3.3 × 10–3 cps (300 sec period) is almost always present.These results suggest that the lifetime of the phase of the oscillation is much longer than that of the amplitude and is likely to exceed one hour. We actually observe the modulation of a wave in smaller wave trains about 11 min long and 20 min apart (average values).Observations with low spatial resolution also suggest that the area of coherence is much greater for the phase than for the amplitude.Kitt Peak National Observatory Contribution No. 425.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
9.
Observations of quiescent prominences with the Zeiss Universal Birefringent Filter at Sacramento Peak show short-lived brightenings and velocity transients in H and D3. The larger events range in area from 25 to 170 square arc sec, have lifetimes of approximately 30 min, velocities of 30 km s–1, and total energy excesses up to 7 × 1027 ergs. These events do not disrupt the stable structure of the prominence, and are interpreted as either condensation events or low energy flares.Visiting astronomer, Sacramento Peak Observatory, operated by the Association of Universities for Research in Astronomy Inc. under contrast AST-78-17292 with the National Science Foundation.Visiting student, Sacramento Peak Observatory, operated by the Association of Universities for Research in Astronomy Inc. under contract AST-78-17292 with the National Science Foundation. 相似文献
10.
Double pass photoelectric observations are presented of five Caii lines (H, K, 8498 Å, 8542 Å, and 8662 Å) in a number of solar plages of different degrees of activity, quiet regions, and a sunspot. The data are compared with previous work. All five lines show increasing emission together in plages and the least opaque of the infrared triplet lines appears to exhibit core emission prior to the more opaque members of the multiplet. The question of source function equality is considered and the differences and similarities among plage profiles and between plage and quiet profiles are shown qualitatively and quantitatively.Staff Member, Laboratory Astrophysics Division, National Bureau of Standards.Visiting Astronomer at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy. Inc., under contract with the National Science Foundation. 相似文献
11.
K. R. Nicolas G. E. Brueckner R. Tousey D. A. Tripp O. R. White R. G. Athay 《Solar physics》1977,55(2):305-319
Spectral line profiles of Si ii and Si iii are presented which were observed both at solar center and near the quiet solar limb with the Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute intensities and line profiles are derived from the photographic data. A brief discussion is given of their center-to-limb variations and of the optical thickness of the chromosphere in these lines. Nonthermal broadening velocities are found for the optically thin lines from their full width at half maximum intensity (FWHM).Also at High Altitude Observatory for part of this work.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
12.
Arch-like features are often seen in spectrograms of very strong lines near the solar limb when the slit crosses the chromospheric network. We show how earlier kinetic-equilibrium (non-LTE) calculations for Ca ii can be used to predict such features for the K line with two-component atmospheric models.Publication of the Goethe Link Observatory, Indiana University, No. 144Now on leave at the High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado. (NCAR is sponsored by the National Science Foundation.) 相似文献
13.
We formulate rate equations for the reaction network coupling H, H–, H+, H2, and H2
+. We attempt to systematize the notation, and to write the equations in a form suitable for modern computational methods of handling the coupled rate equations and radiative transfer equations, for both dynamical and static atmospheres. We have accounted for more processes than are generally considered in most current work; some of these may have an impact on the equilibrium of H– (hence its opacity) and on charge conservation (hence the proton density) in the atmospheres of solar-type stars.Operated by the Association of Universities for Research in Astronomy, Inc. under Contract AST 78-17292 with the National Science Foundation.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
14.
Integrating 26 624 pairs of video frames, the authors have mapped the circular polarization in an active-region filament against
the solar disk by using a traditional magnetograph working at the Hβ line. This filament, offset the disk center, appeared
at the boundary of three decayed active regions. It was quiet and away from any strong enhanced network. The mapped circular
polarization in the filament has an average polarization degree of 1.1×10−3 with a measurement precision of 4×10−4. The mapping of circular polarization in a filament may provide a supplementary diagnosis of the filament magnetic field,
in addition to the mapping of linear polarization via the Hanle effect. However, the interpretation of the circular polarization
requires treatment of the full quantum problem of Zeeman and non-Zeeman effects of Stokes line profiles. 相似文献
15.
R. G. Athay 《Solar physics》1970,12(2):175-185
Profiles are computed for Ha and two Fei lines for a differentially moving atmosphere. The results show that the profiles are asymmetric and that velocity measurements made in the Doppler cores will often lead to erroneous results when the velocity gradient is significant in the regions of the atmosphere where the core forms.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
16.
Wavelengths of clean atmospheric water lines, and some solar lines, in the wavelength interval 10750 Å to 10900 Å have been measured to an accuracy approaching ± 1 mÅ. Strengths and wavelengths have been measured for all atmospheric water lines with absorption coefficients > 5 × 10–4 cm–1 gm–1 cm–2 at 280K, that lie within 15 Å of the He I 10830 Å featur of the stronger He component is affected by a weak water line which reduces atmospheric transmission by nearly 1 % with 10 mm precipitable water in the line of sight.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
17.
Sunspot umbral molecular lines have been used to look for the oscillatory velocities in the umbra. Power spectrum analysis showed conspicuous power for periods in the range between 448 and 310 s. The maximum peak-to-peak amplitude of the umbral oscillatory velocity component is observed to be in the order of 0.5 km s–1.Visiting Astronomer, Solar Division, Kitt Peak National ObservatoryOperated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
18.
A Stokes polarimeter has been built at the High Altitude Observatory to obtain line profiles in both linear and circular polarization in solar spectral lines. These measurements are interpreted using the theory of radiative transfer in the presence of a magnetic field to obtain vector magnetic fields on the solar disk and using the theory of resonance scattering and the Hanle effect to obtain vector magnetic fields in prominences. The polarimeter operates on the Sacramento Peak Observatory 40 cm coronagraph. It is an extensively modified and improved version of an earlier instrument.Polarization modulation is achieved by two KD*P Pockels cells at the coronagraph prime focus and demodulation is by a microprocessor. The instrument control and data handling is done by a minicomputer. Silicon photodiode 128 element line array detectors have replaced the two photomultipliers used on the earlier instrument. This gives a speed increase of a factor of 50.A polarization scrambler provides a chop to a reference beam of unpolarized light by time scrambling the polarization of the solar beam. This device improves sensitivity to polarizations less than 0.01%. The polarization measurements are photon noise limited in most cases. This noise is 0.1% for a typical three second observation which is about one gauss on the longitudinal field and 10 gauss on the transverse field.The National Center for Atmospheric Research is sponsored by The National Science Foundation. 相似文献
19.
Observations of the H272α recombination line towards the galactic centre show features near VLSR= 0, −50 and + 36 kms−1. We have combined the parameters of these features with the available H166α measurements to obtain the properties of the
ionized gas present along the line of sight and also in the ‘3 kpc arm’. For the line-of-sight ionized gas we get an electron
density around 7 cm−3 and a pathlength through it ∼ 10–60 pc. The emission measure and the electron temperature are in the range 500–2900 pc cm−6 and 2000–6000 K. respectively. The ionized gas in the 3 kpc arm has an electron density of 30 cm−3 and extends over 9 pc along the line of sight if we assume an electron temperature of 104 K. Using the available upper limit to the intensity of the H351α recombination line, we show that the distributed ionized
gas responsible for the dispersion of pulsar signals should have a temperature >4500 K. and a minimum filling factor of 20
per cent. We also show that recombination lines from the ‘warm ionized’ gas proposed by McKee & Ostriker (1977) should be
detectable in the frequency range 100–150 MHz towards the galactic centre with the sensitivity available at present. 相似文献
20.
We show that the He i 10830 A line gives reliable Doppler shift measurements in the upper chromosphere above active regions. Persistent flow patterns in active regions observed near the solar limb show features previously noted in Dopplergrams using the Civ transition region ultraviolet emission line. Unlike the Civ measurements, however, the He i absorption shows a strong correlation with the line-of-sight velocity images in certain regions of some active regions.Operated by the Association of Universities for Research in Astronomy, Inc., under contract AST 78-17292 with the United States National Science Foundation.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.Visiting Astronomers, Sacramento Peak Observatory. 相似文献