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1.
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   

2.
The radio radii of the Sun at wavelengths of 5, 10.7, 12, and 95 cm have been determined from eclipse observations as R5 ?? (1.0 ± 0.015)R ??, R 10,12 = (1.05 ± 0.003)R ??, and R 95 = (1.2 ± 0.02)R ??. The bright-ness temperatures of quiet solar disk areas at these wavelengths have turned out to be Td 5 = (22 ± 2) × 103, Td 10 = (44 ± 3) × 103, Td 12 = (47 ± 3) × 103, and Td 95 = (1000 ± 30) × 103 K. There were local sources of radio emission with angular sizes from 1.9 to 2.4 arcmin and brightness temperatures from 80 × 103 to 1.75 × 106 K above sunspot groups at short wavelengths of 5, 10.7, and 12 cm. The radio flux from the local sources at 95 cm turned out to be below the detection threshold of 1.0 × 10?22 W m?2 Hz?1. Comparison of the values obtained with the results of observations of another eclipse on August 1, 2008, occurred at the epoch of minimum of the 11-year solar cycle has shown that the radio radius of the Sun at 10.7 and 12 cm increased from 1.016 R ?? to 1.05 ± 0.003R ??, the height of the emitting layer at these wavelengths moved from 11 × 103 km to (30 ± 7) × 103 K, and the brightness temperature of the quiet Sun rose from (35.8 ± 0.4) × 103 K to (44 ± 3) × 103 K at 10.7 cm and from (37.3 ± 0.4) × 103 K to (47 ± 3) × 103 K at 12 cm. Consequently, the parameters of the solar atmosphere changed noticeably in 2 years in connection with the beginning of the new solar cycle 24. The almost complete absence of local sources at the longest wavelength of 95 cm suggests that the magnetic fields of the sunspot groups on January 4, 2011, were weak and did not penetrate to the height from where their emission could originate. If this property is inherent in most sunspot groups of cycle 24, then it can be responsible for its low flare activity.  相似文献   

3.
The eclipse observations were performed at the Laboratory of Radio Astronomy of the CrAO in Katsiveli with stationary instrumentation of the Solar Patrol at wavelengths of 10.5 and 12.0 cm. The data obtained were used to determine the brightness temperature of the undisturbed Sun at solar activity minimum between 11-year cycles 23 and 24: T d10.5 = (43.7 ± 0.5) × 103 K at 10.5 cm and T d12.0 = (51.8 ± 0.5) × 103 K at 12.0 cm. The radio brightness distribution above the limb group of sunspots NOAA 0866 was calculated. It shows that at both wavelengths the source consisted of a compact bright nucleus about 50 × 103 km in size with temperatures T b10.5 = 0.94 × 106 K and T b12.0 = 2.15 × 106 K located, respectively, at heights h 10.5 = 33.5 × 103 km and h 12.0 = 43.3 × 103 km above the sunspot and an extended halo with a temperature T b = (230–300) × 103 K stretching to a height of 157 × 103 km above the photosphere. The revealed spatial structure of the local source is consistent with the universally accepted assumption that the radiation from the bright part of the source is generated by electrons in the sunspot magnetic fields at the second-third cyclotron frequency harmonics and that the halo is the bremsstrahlung of thermal electrons in the coronal condensation forming an active region. According to the eclipse results, the electron density near the upper boundary of the condensation was N e ≈ 2.3 × 108 cm?3, while the optical depth was τ ≈ 0.1 at an electron temperature T e ≈ 106 K. Thus, the observations of the March 29, 2006 eclipse have allowed the height of the coronal condensation at solar activity minimum to be experimentally determined and the physical parameters of the plasma near its upper boundary to be estimated.  相似文献   

4.
We describe the technique and results of modelling the solar radio emission during the maximum phase of the solar eclipse of March 29, 2006 on the RATAN-600. The aim of modelling is to refine the brightness temperature of the solar corona at the distances up to two solar radii from the center of the optical disk of the Sun. We obtained the distribution of brightness temperature in the vicinity of the coronal hole above the solar North Pole at the wavelength of 13 cm. The results of modelling showed that brightness temperatures of the coronal hole at the distances greater than 1.02 RC (here RC is the radius of the optical disk of the Sun) is substantially lower than the expected average brightness temperature of a typical coronal hole, and that of the quiescent Sun (below 30000 K) at the wavelength of 13 cm. The classical Baumbach-Allen formula for electron density in a spherically symmetric corona agrees with the results of observations starting at distances of (1.4–1.5) RC.  相似文献   

5.
Two extreme ultraviolet (EUV) spectrophotometers flown in December 1978 on Venera 11 and Venera 12 measured the hydrogen Lyman α emission resonantly scattered in the atmosphere of Venus. Measurements were obtained across the dayside of the disk, and in the exosphere up to 50,000 km. They were analyzed with spherically symmetric models for which the radiative transfer equation was solved. The H content of the Venus atmosphere varies from optically thin to moderately thick regions. A shape fit at the bright limb allows one to determine the exospheric temperature Tc and the number density nc independently of the calibration of the instrument or the exact value of the solar flux. The dayside exospheric temperature was measured for the first time in the polar regions, with Tc = 300 ± 25°K for Venera 11 (79°S) and Tc = 275 ± 25°K (59°S) for Venera 12. At the same place, the density is nc = 4?2+3 × 104 atom.cm?3, and the integrated number density Nt from 250 to 110 km (the level of CO2 absorption) is 2.1 × 1012 atom.cm?2, a factor of 3 to 6 lower than that predicted in aeronomical models. This probably indicates that the models should be revised in the content of H-bearing molecules and should include the effect of dynamics. Across the disk the value of Nt decreases smoothly with a total variation of two from the morning side to the afternoon side. Alternately it could be a latitude effect, with less hydrogen in the polar regions. The nonthermal component if clearly seen up to 40,000 km of altitude. It is twice as abundant as at the time of Mariner 10 (solar minimum). Its radial distribution above 4000 km can be simulated by an exospheric distribution with T = 1030K and n = 103 atom.cm?3 at the exobase level. However, there are less hot atoms between 2000 and 4000 km than predicted by an ionospheric source. A by-product of the analysis is a determination of a very high solar Lyman α flux of 7.6 × 1011 photons (cm2 sec Å)?1 at line center (1 AU) in December 1978.  相似文献   

6.
The occultation of the Pioneer 10 spacecraft by Io (JI) provided an opportunity to obtain two S-band radio occultation measurements of its atmosphere. The dayside entry measurements revealed an ionosphere having a peak density of about 6 × 104 elcm?3 at an altitude of about 100 km. The topside scale height indicates a plasma temperature of about 406 K if it is composed of Na+ and 495 K if N2+ is principal ion. A thinner and less dense ionosphere was observed on the exit (night side), having a peak density of 9 × 103 elcm?3 at an altitude of 50 km. The topside plasma temperature is 160 K for N2? and 131 K for Na+. If the ionosphere is produced by photoionization in a manner analogous to the ionospheres of the terrestrial planets, the density of neutral particles at the surface of Io is less than 1011?1012 cm3, corresponding to a surface pressure of less than 10?8 to 10?9 bars. Two measurements of its radius were also obtained yielding a value of 1830 km for the entry and 192 km for the exit. The discrepancy between these values may indicate an ephemeris uncertainty of about 45 km. The two measurements yield an average radius of 1875 km, which is not in agreement with the results of the Beta Scorpii stellar occultation.  相似文献   

7.
The radiative lifetimes of cometary OH are calculated as a function of the heliocentric velocity of the comet and the velocity distributions of the product atoms are determined. At a distance of 1 AU from the Sun, the lifetimes vary between 1.2×105 and 1.9×105 sec at solar minimum and between 1.0×105 and 1.4×105 sec at solar maximum, depending upon velocity. Continuous absorption into the repulsive 12Σ- state is major destruction path. The calculated lifetimes are generally consistent with the lifetimes inferred from observations, but suggest some elaboration of the models is necessary. Photodissociation of OH produces a low-velocity component of hydrogen atoms at 8 km sec?1 relative to the parent OH molecule and a high-velocity component between 17 and 27 km sec?1. Photodissociation of OH leads to metastable O(1D) and O(1S) and is an additional source of the red and green line emission of atomic oxygen. The lifetime of OD is estimated to be about 4.3× 105 sec at solar minimum and 2.6×105 sec at solar maximum so that the OD/OH ratio in comets is enhanced relative to the HDO/H2O production ratio by a factor between 2 and 3. Photodissociation of OD produces only high-velocity D atoms with a mean value of 17 km sec?1.  相似文献   

8.
Two coherently related radio signals transmitted from Voyager 1 at wavelengths of 13 cm (S-band) and 3.6 cm (X-band) were used to probe the equatorial atmosphere of Titan. The measurements were conducted during the occultation of the spacecraft by the satellite on November 12, 1980. An analysis of the differential dispersive frequency measurements did not reveal any ionization layers in the upper atmosphere of Titan. The resolution was approximately 3 × 103 and 5 × 103 electrons/cm3 near the evening and morning terminators, respectively. Abrupt signal changes observed at ingress and egress indicated a surface radius of 2575.0 ± 0.5 km, leading to a mean density of 1.881 ± 0.002 g cm?3 for the satellite. The nondispersive data were used to derive profiles in height of the gas refractivity and microwave absorption in Titan's troposphere and stratosphere. No absorption was detected; the resolution was about 0.01 dB/km at the 13-cm wavelength. The gas refractivity data, which extend from the surface to about 200 km altitude, were interpreted in two different ways. In the first, it is assumed that N2 makes up essentially all of the atmosphere, but with very small amounts of CH4 and other hydrocarbons also present. This approach yielded a temperature and pressure at the surface of 94.0 ± 0.7°K and 1496 ± 20 mbar, respectively. The tropopause, which was detected near 42 km altitude, had a temperature of 71.4 ± 0.5°K and a pressure of about 130 mbar. Above the tropopause, the temperature increased with height, reaching 170 ± 15°K near the 200-km level. The maximum temperature lapse rate observed near the surface (1.38 ± 0.10°K/km) corresponds to the adiabatic value expected for a dry N2 atmosphere—indicating that methane saturation did not occur in tbis region. Above the 3.5-km altitude level the lapse rate dropped abruptly to 0.9 ± 0.1°K/km and then decreased slowly with increasing altitude, crossing zero at the tropopause. For the N2 atmospheric model, the lapse rate transition at the 3.5-km level appears to mark the boundary between a convective region near the surface having the dry adiabatic lapse rate, and a higher stable region in radiative equilibrium. In the second interpretation of the refractivity data, it is assumed, instead, that the 3.5 km altitude level corresponds to the bottom of a CH4 cloud layer, and that N2 and CH4 are perfectly mixed below this level. These assumptions lead to an atmospheric model which below the clouds contains about 10% CH4 by number density. The temperature near the surface is about 95°K. Arguments concerning the temperature lapse rates computed from the radio measurements appear to favor models in which methane forms at most a limited haze layer high in the troposphere.  相似文献   

9.
The u.v. spectrometer polarimeter on the Solar Maximum Mission has been utilized to measure mesospheric ozone vs altitude profiles by the technique of solar occultation. Sunset data are presented for 1980, during the fall equinoctal period within ± 20° of the geographic equator. Mean O3, concentrations are 4.0 × 1010 cm?3at 50 km, 1.6 × 1010 cm?3 at 55 km. 5.5 × 109 cm?3 at 60 km and 1.5 × 109 cm?3 at 65 km. Som profiles exhibit altitude structure which is wavelike. The mean ozone profile is fit best with the results of a time-dependent model if the assumed water vapor mixing ratio employed varies from 6 ppm at 50 km to 2–4 ppm at 65 km.  相似文献   

10.
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   

11.
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   

12.
The theory of plasma emission is developed under the assumption that the Langmuir waves are generated by an isotropic distribution of fast electrons. Emission from inverse power-law distributions tend to favor emission at the second harmonic with brightness temperatures up to about 108 K at 100 MHz. The concept of a gap (in velocity space) distribution is developed. Very bright plasma emission can result from a gap distribution. For brightness temperatures between 109 K and 1011 K for the second harmonic the fundamental has a brightness temperature between 108 K and 109 K. For higher brightness temperatures the fundamental is amplified and can be very much brighter than the second harmonic. The maximum brightness temperatures for the fundamental and second harmonic at 100 MHz are about 1016 K and 1013 K respectively. Mechanisms by which a gap distribution might be formed are discussed and two effective mechanisms are identified. The theory is applied to the interpretation of radio bursts of types I, II, stationary IV and V. In each case the suggested mechanism appears to be favorable.  相似文献   

13.
The Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe eight solar bursts at 2, 6, or 20 cm wavelength with second-of-arc angular resolution. The regions of burst energy were all resolved with angular sizes between 5″ and 30″, brightness temperatures between 2 × 107 K and 2 x 108 K, and degrees of circular polarization between 10 and 90%. A series of 10 s snapshot maps are presented for the more intense bursts, and superimposed on photospheric magnetograms or Hα photographs. The impulsive phase of the radio bursts is located near the magnetic neutral line of the active regions, and between the flaring Hα kernels which mark the footpoints of magnetic loops. The impulsive phase of one 6 cm burst was smaller and spatially separated from both the preburst radio emission and the gradual decay phase of the burst. Another 6 cm burst exhibited preburst heating of the coronal loop in which the burst occurred. The plasma was probably heated at a lower level in the loop, while the burst energy was released several minutes later at a higher level. A multiple-spike 20 cm burst exhibited polarity inversions with degrees of circular polarization of 90%. The rapid changes in circular polarization are attributed to either a magnetically complex region or the emersion of new magnetic flux at coronal heights where magnetic field strengths H ≈ 300 to 400 G.  相似文献   

14.
Two density profiles of the thermospheric nitric oxide were obtained by means of the γ(1,0) band airglow measured with rocket-home radiometers flown from Uchinoura, Japan (31°N) at around autumnal equinoxes in 1982 and 1983. The peak densities were found at altitudes of 105–110 km and are 9 × 107 and 7 × 107 cm−3, respectively. They are well reproduced by the variation of solar activity in terms of a one-dimensional photochemical-diffusive model, but the densities above 140 km under moderate solar activity differ considerably from the model prediction. A similar discrepancy has already been found in the NO density profile obtained by our previous experiment at solar maximum. These discrepancies infer a possibility either that our understanding of thermospheric nitrogen chemisty includes a serious error, or that the meridional circulation affects considerably the NO density profile even at altitudes above 140 km and at low latitudes.  相似文献   

15.
From the photographs taken at the total solar eclipse of 11 June 1983, we derived the electron density for the north polar rays and for the thread-like fine structures above the active region, which are 108 at 1.4 solar radii and 3×109 at 1.15 solar radii, respectively. The brightness distributions of the corona at the polar region and above the active region, and the flattening index were also derived.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

16.
Unique timelapse sequences of Skylab/ATM spectroheliograms reveal the following characteristics of normal (i.e. non-flare) loop structures in the solar atmosphere:
  1. At the 0.5 × 106 K temperature of Ne vii, emission is concentrated into individual spiky structures that project 104–105 km from their magnetic footpoints and live on the order of 30 min.
  2. At the 1.0 × 106 K temperature of Mg ix, the individual spikes are more diffuse, and have greater lengths and longer lifetimes (～ 1.5 hr) than their 0.5 × 106 K counterparts. Perhaps for this reason, more 1.0 × 106 K loops are visible than 0.5 × 106 K loops at any given time.
  3. At the 2.0 × 106 K temperature of Fe xv, emission is confined to a number of relatively diffuse and irregularly shaped features whose collective patterns define closed field volumes in and between active regions. Although the individual features evolve on a time scale of roughly 6 hr, their collective patterns last for several days or more. Unlike the 0.5 × 106 K features, the 2.0 × 106 K features never form as a linear extension along an apparent magnetic field line, but seem to brighten and fade in place.
These results place severe constraints on theoretical models of coronal heating and mass flow.  相似文献   

17.
Kulagin  E.S.  Kouprianov  V.V. 《Solar physics》2004,219(1):79-86

A distribution map of the large-scale chromospheric Doppler velocities on the solar disk for 5 June 2002 is presented. The map was obtained using a 2D-spectroscopy technique within the He?i 10830 Å line. The spatial resolution of the map is about 30 arc sec. The map demonstrates a downflow in the chromosphere over active regions, especially significant around the spots and inside the plages. Positive Doppler velocities correspond to strong magnetic field areas, regardless of the field sign. Three major chromospheric outflow zones are observed: an equatorial and two polar ones. Each area of substantial negative Doppler velocities matches a zone of weak intensity of inner corona observed within the Fe?ix-x 171 Å line by the SOHO spacecraft. A Doppler velocity histogram and the dependence of the Doppler velocities on the cosine of the heliocentric angle for the solar disk are calculated. The total mass outflow from the upper chromosphere is estimated as 2×1013 g s?1. Four percent of this amount is sufficient to produce the fast solar wind.

  相似文献   

18.
The space density of life-bearing primordial planets in the solar vicinity may amount to ～8.1×104?pc?3 giving total of ～1014 throughout the entire galactic disk. Initially dominated by H2 these planets are stripped of their hydrogen mantles when the ambient radiation temperature exceeds 3?K as they fall from the galactic halo to the mid-plane of the galaxy. The zodiacal cloud in our solar system encounters a primordial planet once every 26 My (on our estimate) thus intercepting an average mass of 103 tonnes of interplanetary dust on each occasion. If the dust included microbial material that originated on Earth and was scattered via impacts or cometary sublimation into the zodiacal cloud, this process offers a way by which evolved genes from Earth life could become dispersed through the galaxy.  相似文献   

19.
From photographic recordings of some hundred bright Ca+-network cells on the solar disk we find evidence for a smaller size of polar cells as compared to equatorial cells by a factor of about 0.9. We do not find an indication of a dependence of the structure of the cells on the heliographic position.  相似文献   

20.
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   

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