首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
A rocket-borne coronagraph utilizing external occulting disks was used to photograph the solar corona from 3 to 9 R s at 1931 UT on 7 March, 1970. Comparison of the rocket and ground-based observations shows a one-to-one correspondence between major streamers from the inner to the outer corona. In particular streamers over the poles are clearly visible against the background corona from 3 to 8 R s. These rocket data had a scattered light level of 1.2 × 10–10 B s. The derived quiet equatorial and polar K + F corona was within 10% of the absolute brightness of standard coronal models and displayed identical radial gradients to those models. The photometric profiles of the NE limb streamer were analyzed assuming a model in which the core density follows a Gaussian distribution in directions perpendicular to the radius vector. This streamer was assumed to be rooted on the visible disk at 55 to 60° from the plane-of-the-sky as based on K-coronameter and XUV data. An uncertainty of as much as a factor of three still remains for the value of the axis density owing to uncertainty in the line-of-sight dimension of the streamer.  相似文献   

2.
A large equatorial coronal streamer observed in the outer corona (3R ) grew in brightness and size during successive limb passages between October 6, 1973 and January 10, 1974 (solar rotations 1606–1611). Unlike previous studies of streamers and their photospheric associations, no definite surface feature could be identified in the present case. This suggests that the streamer is associated with the large scale photospheric magnetic field. Comparison of the streamer growth with observed underlying photospheric magnetic flux changes indicated that as the streamer increased in brightness, areal extent, and density, the photospheric magnetic flux decreased. Three possible explanations for the streamer's growth are presented; the conceptually simplest being that the decrease in photospheric field results in an opening of the flux tubes under the streamer which permits an increased mass flux through the streamer.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

3.
The analysis of a storm of type III solar radio bursts observed in August 1968 between 5 and 0.2 MHz by the RAE-1 satellite has yielded the storm morphology, a possible relation to meter and decameter storms, and an average exciter speed of 0.37 c between 10 and 40 R (Fainberg and Stone, 1970a, b). A continuation of the analysis, based on the apparent dependence of burst drift rate on heliographic longitude of the associated active region, now provides a distance scale between plasma levels in the streamer, an upper limit to the scale size of coronal streamer density inhomogeneities, and an estimate of the solar wind speed. By fixing one level the distance scale is utilized to determine the electron density distribution along the streamer between 10 and 40 R . The streamer density is found to be 16 times that expected for the solar minimum quiet solar wind. An upper limit to the scale size of streamer density inhomogeneities is estimated to be of the order of 1 or 2 solar radii over the same height range. From the progressive delay of the central meridian passage (CMP) of the lower frequency emission, a streamer curvature is inferred which in turn implies an average solar wind speed of 380 km/sec between 14 and 36 R within the streamer.  相似文献   

4.
Slitless spectra of the chromosphere, observed cinematographically at the total solar eclipse of 10 July 1972, were reduced. The surface brightness distribution of the helium D3 line in the undisturbed chromosphere was obtained in agreement with results by other observers. The available eclipse data on the D3 absolute brightness was analysed by means of theoretical curves of growth. Intensity data by some observers were found to be certainly too high. A trend was found that the D3 absolute brightness in the quiet chromosphere decreases with the increasing solar activity (sunspot number). This perhaps indicates a variation of the spicule number over the solar surface during a sunspot cycle.  相似文献   

5.
An analysis of 1210 visual brightness estimations of the Moon's ashen light is presented, performed by a working group of amateur astronomers from June 1972 to December 1973. In the Moon phase interval 0.1 T b 0.7 the brightness expressed in a semi-empirical scale, S G, is found to be linearly related to the phase. Monthly deviations from the mean brightness show well defined winter maxima (January) and summer minima (July). Within the referenced period the brightness of the ashen light tends to increase, whereas the solar magnetic activity decreased. In addition, minor correlations and, respectively, anti-correlations are found at stratospheric temperature and, respectively density. On account of the nature of the ashen light its variations are regarded as fluctuations of the Earth's albedo.  相似文献   

6.
Observations of the solar eclipse on March 29, 2006, at the Laboratory of Radio Astronomy of the CrAO showed that the radio radius of the Sun at a wavelength of 1 m in the direction of the first contact was R d = 1.12 R ⊙ during solar activity minimum between cycles 23 and 24. The brightness temperature of the undisturbed Sun was T d = (0.6 ± 0.06) × 106 K. There was a noise storm source above the sunspot group NOAA 0865 whose bright nucleus had a size of 1′.3 and a brightness temperature T b = 16 × 106 K. The noise storm bursts were emitted from the region of the bright nucleus above the group NOAA 0865 and were absent during its covering by the disk of the Moon. Thermal radiation from a coronal condensation with a brightness temperature of (1?2) × 106 K extending out from the visible solar disk to 2′.7 was observed during the eclipse above the eastern limb sunspot group NOAA 0866. The bright nucleus in this limb source appeared 42 min after eclipse termination and persisted in the ensuing days. This may be indicative of the time of its emergence from behind the radio horizon formed by regular refraction of radio waves in the corona. The refractive displacement was measured by comparison with the eclipse observations at a shorter wavelength of 12 cm. Its value of 0′.96 is close to the calculated value of 0′.8.  相似文献   

7.
A study of the background corona near solar minimum   总被引：2，自引：0，他引：2  
The white light coronagraph data from Skylab is used to investigate the equatorial and polarK andF coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona is dominated by either streamers or coronal holes seen in projections on the limb approximately 50% and 30% of the time, respectively; (2) despite the domination by streamers and holes, two periods of time were found which were free from the influences of streamers or holes (neither streamers nor holes were within 30° in longitude of the limb); (3) the derived equatorial background density model is less than 15% below the minimum equatorial models of Newkirk (1967) and Saito (1970); (4) a spherically symmetric density model for equatorial coronal holes yields densities one half those of the background density model; and (5) the inferred brightness of theF-corona is constant to within ±10% and ±5% for the equatorial and polar values, respectively, over the observation period. While theF-corona is symmetric at 2R it begins to show increasing asymmetry beyond this radius such that at 5R the equatorialF-coronal brightness is 25% greater than the polar brightness.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

8.
An analytical expression is obtained for the K-corona brightness as a function of the distance from the solar limb. The agreement of the theory with the numerous observational data indicates that the density distribution at the levels located at 1.2–2.5 R heliocentric distances may be treated as hydrostatic with T = const. The deviation of the observed K-corona brightness from the expression obtained may be indicative of supersonic fluxes of matter. These concepts may be used to verify the various theoretical models for solar wind source.  相似文献   

9.
A computer program to convolve numerically any azimuthally symmetric, solar radial brightness distribution with standard antenna patterns of small half power beamwidths has been used to find a solar brightness distribution which is a good fit to the eclipse curve obtained during the 7 March 1970 partial solar eclipse with the NRAO 36-ft antenna at 3.5 mm. This brightness distribution is compared with the brightness distribution at 3.2 mm determined by the Pennsylvania State University Radio Astronomy Observatory group during the same eclipse but observed from Mexico where totality occurred. The two brightness distributions are very similar in shape, showing a double peak near the limb, but differing slightly in the positions of the peaks.  相似文献   

10.
Richard Woo 《Solar physics》2007,241(2):251-261
In the absence of magnetic field measurements of the solar corona, the density structure of white-light images has provided important insight into the coronal magnetic field. Recent work sparked by highly sensitive radio occultation measurements of path-integrated density has elucidated the density structure of unprocessed solar eclipse pictures. This paper does the same for processed images that reveal low-contrast small-scale structures, specifically Koutchmy’s edge-enhanced white-light image of the 11 August 1999 solar eclipse. This processed image provides visual evidence for two important results deduced from radio occultation measurements of small-scale density variations. First, in addition to the closed loops readily seen at the base of the corona in high-resolution EUV and soft X-ray images, open filamentary structures permeate the corona including active regions generally thought to be magnetically closed. Observed at the image resolution, the filamentary structures are 1° wide in latitude and an order of magnitude smaller than polar plumes. Second, although inhomogeneities that are convected along with the solar wind are also present, filamentary structures dominate the image because of their steeper density gradients. The quantitative profile of polarized brightness (pB) at the base of the corona shows that the filamentary structures have transverse density gradients that are proportional to their density. This explains why edge-enhanced images, limited in sensitivity to density gradients, tend to detect filamentary structures more readily in high-density regions (e.g., active regions, streamer stalks, and prominences) than in low-density polar coronal holes, and why filamentary structures seem more prevalent in solar eclipse pictures during solar maximum. The pB profile at the base of the corona also fills the gap in Doppler measurements there, reinforcing that open ultra-fine-scale filamentary structures observed by the radio measurements are predominantly radial and that they are an integral part of the radial expansion of the solar wind.  相似文献   

11.
Eselevich  V.G.  Eselevich  M.V. 《Solar physics》1999,188(2):299-313
It is shown that within R>3–4 Rfrom the solar center the coronal streamer belt consists in a sequence of radial brightness rays. A minimum angular size of the individual ray d2.0°–2.5°, which is about the same in the directions normal to and along the streamer-belt, is independent of the distance from the Sun at R=4–6 R. The lifetime of the rays can exceed 10 days. From time to time, inhomogeneities of material inside the rays begin to move in the antisunward direction. Plots of increase in their velocity with the distance from the Sun are similar to those obtained by Sheeley et al. (1997) for inhomogeneities that are carried by a quasi-stationary solar wind in streamers. It is concluded that the phenomena discussed in this paper and by Sheeley et al. (1997) share a common origin. It is suggested that a different origin of solar wind flows in streamers and in coronal holes may be associated with a different character of flows in microtubes of the magnetic field comprising a total solar wind flow. These tubes are observed as brightness rays in streamer belts and plumes in coronal holes.  相似文献   

12.
Observations of the white light corona were made on over 900 days during the years 1964–67 at heights between 1.125 and 2.0 R with the K-coronameter at Mount Haleakala and Mauna Loa, Hawaii. The brightness distribution of the minimum corona was elliptical with average equatorial intensities three times the polar. Coronal features of the new cycle at 1.125 R occurred predominantly in the sunspot zones at 25–30° latitude and in a high latitude zone which migrated toward the North pole before solar maximum. The brightness of the inner corona doubled over this period and a close association is found between the average corona and 10.7-cm solar radio flux. Electron densities in the equatorial regions were nearly twice those of Van de Hulst's model corona, in agreement with the results of recent eclipse observations.At Hawaii Institute of Geophysics.  相似文献   

13.
A model of the chromosphere and transition zone for quiet regions of the Sun is given.The height dependence of temperature and density are different for the borders of the supergranules and for their inner parts. The difference is caused by the enhanced mechanical energy flux at the places of strengthened magnetic field.The average dependence of density on height is given by eclipse data, the corresponding values for temperatures are obtained by a trial and error method using calculation of solar radio emission for different wavelengths and comparison with observations.The adopted model is consistent with observational data on the solar visual, radio and UV emission. This model also accounts for the brightness distribution on spectroheliograms taken in H wings, K232 Caii and in several UV spectral lines.  相似文献   

14.
As a result of a collaborative rocket experiment carried out during the solar eclipse on 7 March, 1970, measurements have been made of the brightness of Lyman from the corona, at heights between 5 × 104 and 5 × 105 km above the limb. The emission is shown to occur primarily through the resonance scattering of chromospheric Lyman from the residual neutral hydrogen in the corona. Both the absolute value and radial fall-off of the brightness agree well with calculations based on solar density models. The Lyman emission has similar variations around the limb to the white light corona, showing in particular an equatorial enhancement.  相似文献   

15.
The spectrum of the solar corona obtained during the eclipse of 7 March, 1970 has been studied. From the analysis of the line halfwidths it is concluded that the emission of coronal lines of various groups arises in different volumes of the corona. The lines 5303 and 4231 are analyzed in detail and by the use of the equations of excitation and ionization balance. The distribution of electron temperature T e and density n e vs height in the solar corona has been found. The usually adopted n e and T e are noticeably less than those values obtained in present analysis. This discrepancy may be due to the fact that the considered area of the corona seems to be in an unusual condition.  相似文献   

16.
We review the photometric work on eclipse reappearances of Io. New observations of eclipse reappearances of Io confirm the post-eclipse brightness anomaly reported by Binder and Cruikshank (1964) but testify to its intermittent nature. A post-eclipse anomaly of approximately 0.07 mag was observed on two occasions in 1972, while observations of Europa and Ganymede showed no brightness anomaly greater than 0.01 mag. The atmospheric condensation model for the anomaly on Io is reviewed in terms of the quantity of frost required to produce the effect and the corresponding amount of gas liberated to the atmosphere upon sublimation. The observational data and the results from a stellar occultation are in general accord with the theoretical predictions of the stability of heavy gases on Io, while both observational and theoretical criteria are satisfied by a tenuous atmosphere of a heavy gas such as methane or ammonia having a surface pressure ～10?7 bar.  相似文献   

17.
The radio observations of the coronal streamers obtained using Clark Lake radioheliograph at 73.8, 50.0, and 38.5 MHz during a period of minimum activity in September 1986 are presented. Streamers appear to correlate with two prominent disk sources whose intensities fluctuated randomly. The variations in half-power diameter of the radio Sun are found to correspond with the variations in the white-light extents of the coronal streamers. It appears that the shape of the radio Sun is not a function of the phase of the solar cycle; instead it depends on the relative positions of the streamers in the corona. The observed peak brightness temperatures,T B , of the streamers are found to be very low, being 6 × 104 K.We compute the brightness temperature distribution along the equator by tracing the rays in the coronal plasma. The rays are deflected away by the streamers before reaching the critical density level, whereas they penetrate deeper into the coronal hole for small angles between the line of sight and the streamer axis. As a consequence, it is found that the streamers and coronal holes appear in the calculated equatorial brightness distribution as irregular brightness depressions and enhancements, respectively. The fine structures are found to disappear when the scattering due to small-scale density inhomogeneities is included in the ray-tracing calculations. The required relative level of density fluctuations, 1 = N/N, is found to be greater than 12% to reduce the peak brightness temperature from 106 K to 6 × 104 K for all the three frequencies.On leave from Indian Institute of Astrophysics, Bangalore 560034, India.  相似文献   

18.
Eselevich  V.G.  Fainshtein  V.G.  Eselevich  M.V. 《Solar physics》2001,200(1-2):259-281
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   

19.
A unique combination of photographic and K-coronameter data were used to study the structure and evolution of two known coronal streamers. In addition, two other K-coronameter enhancements were studied as representing ideal second examples of the known streamers. As a general rule the observations indicate that these features were direct coronal manifestations of photospheric bipolar magnetic regions (BMR) and were of two basic types:active region, by which is meant a coronal streamer which develops radially over a low-latitude active region; andhelmet which denotes a streamer whose structure and development appear to be a consequence of a long-lived complex of activity, composed of both trailing magnetic fields and a parent center of disk activity.The similarity of growth rates during the first solar rotation of life led to derivation of a total streamer density of 4–5 × 108 cm–3 atr = 1.125R . This density may represent a characteristic maximum density at the base of streamers. The intensity gradient of the inner (r1.5R ) corona was used to establish a qualitative evolutionary model of streamers which synthesizes the observations. Briefly, streamers initially develop over active regions; the streamer growth rate may be as rapid as the disk activity, or at worst lags flare activity by solar rotation. The streamer can be the cause of interplanetary and geomagnetic effects at 1 AU within a solar rotation after birth. Thereafter the streamer follows an evolution dictated by the underlying solar magnetic fields. In any case the lowest level of the coronal enhancement has a lifetime not exceeding that of the solar disk activity.  相似文献   

20.
C. F. Keller 《Solar physics》1971,21(2):425-429
White-light photographs of the solar corona were taken during the March 1970 eclipse from an Air Force NC-135 jet aircraft at an altitude of 36 380 ft. Four photographs each were made for several exposure times varying from 0.1 to 10.0 s. Three each were made with plane polaroid filters whose orientation was varied at 60° intervals. Stabilization of the camera was approximately 10 even during the longest exposures. The corona was recorded to distances beyond 12 R .A preliminary study of per cent polarization as a function of position with respect to the solar disk for a set of 1.0 s exposures shows an inversion in per cent polarization in the region 6 to 8 R -polarization decreasing outward to the region and increasing again beyond it. This inversion is most apparent along the major streamers.Intensities traced outward from the Sun in both polar and equatorial directions are compared with previous observations.Work done under the auspices of the U.S. Atomic Energy Commission.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号