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1.
P. R. Wilson 《Solar physics》1974,35(1):111-121
This paper considers the recent criticism by Mullan (1973) of sunspot models and the cooling mechanism which I have proposed in Papers I, II and III of this series. The discussion of the cooling produced by an idealized flow cycle has been extended to include vertical temperature gradients which are consistent with a convectively unstable atmosphere. This leads to an expression for Mullan's parameter f (the ratio in which estimates of the energy flux based on an idealized Carnot cycle should be reduced) which is appropriate to this situation. It is shown that, for a cycle similar to that of Paper III, f = 0.82, while for one which has a vertical extent of order 5 Mm, f= 0.4. Hence the energy flux which, in principle, can be transported away from a sunspot by such a cycle is conservatively estimated to be 1.1 × 1029 erg s?1 compared with a typical sunspot energy deficit of 2.2 × 1029 erg s?1. Other criticisms relating to the magnetic field amplification and the ‘cool one’ model are discussed. It is concluded that the essential features of these models remain valid and that the modifications suggested by Mullan's criticism greatly increase their applicability to the sunspot problem.  相似文献   

2.
Characteristic times for heating and cooling of the thermal X-ray plasma in solar flares are estimated from the time profile of the thermal X-ray burst and from the temperature, emission measure and over-all length scale of the flare-heated plasma at thermal X-ray maximum. The heating is assumed to be due to magnetic field reconnection, and the cooling is assumed to be due to heat conduction and radiation. Temperatures and emission measures derived from UCSD OSO-7 X-ray flare observations are used, and length scales are obtained from Big Bear large-scale Hα filtergrams for 17 small (subflare to Class 1) flares. The empirical values obtained for the characteristic times imply (1) that flares are produced by magnetic field reconnection, (2) that conduction cooling of the thermal X-ray plasma dominates radiative cooling and (3) that reconnection heating and conduction cooling of the thermal X-ray plasma are approximately in balance at thermal X-ray maximum. This model in combination with the data gives estimates for the electron number density (1010–1011 cm?3) and the magnetic field strength (10–100 G) in the thermal X-ray plasma and for the total thermal energy generated in a subflare (≈ 1030 erg for an Hα area ≈ 1 square degree) which agree with previous observational and theoretical estimates obtained by others.  相似文献   

3.
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4.
We present analyses of new optical photometric observations of three W UMa-type contact binaries FZ Ori, V407 Peg and LP UMa. Results from the first polarimetric observations of the FZ Ori and V407 Peg are also presented. The periods of FZ Ori, V407 Peg and LP UMa are derived to be 0.399986, 0.636884 and 0.309898 d, respectively. The O?C analyses indicate that the orbital periods of FZ Ori and LP UMa have increased with the rate of 2.28×10?8 and 1.25×10?6 d?yr?1, respectively and which is explained by transfer of mass between the components. In addition to the secularly increasing rate of orbital period, it was found that the period of FZ Ori has varied in sinusoidal way with oscillation period of ～30.1 yr. The period of oscillations are most likely to be explained by the light-time effect due to the presence of a tertiary companion. Small asymmetries have been seen around the primary and secondary maxima of light curves of all three systems, which is probably due to the presence of cool/hot spots on the components. The light curves of all three systems are analysed by using Wilson-Devinney code (WD) and the fundamental parameters of these systems have been derived. The present analyses show that FZ Ori is a W-subtype, and V407 Peg and LP UMa are A-subtype of the W UMa-type contact binary systems. The polarimetric observations in B, V, R and I bands, yield average values of polarization to be 0.26±0.03, 0.22±0.02, 0.22±0.03 and 0.22±0.05 per cent for FZ Ori and 0.21±0.02, 0.29±0.03, 0.31±0.01 and 0.31±0.04 per cent for V407 Peg, respectively.  相似文献   

5.
It is shown that the mean value for the heat flow of a gravitationally-differentiated Moon of fission origin is about 13 erg cm?2 s?1 and that the heat flow varies regionally from about 3 erg cm?2s?1 to more than 45 erg cm?2s?1. These regional variations in the heat flow are caused by a non-uniform distribution of K, U and Th in the KREEP zone at the crust-upper mantle boundary and the redistribution of crustal materials and K, U and Th rich KREEP materials by basin-forming impacts. The scale of these regional variations is hundreds of km. The models presented are in accord with the Apollo 15 and 17 heat flow measurements.  相似文献   

6.
The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016.  相似文献   

7.
Mid-infrared extinction coefficients of five natural amorphous silicates and seven synthetic glasses were measured. Three bands at about 10, 12, and 20 μm were seen for all the measured samples. The quantities of these bands are found to have good correlations with the SiO2 content of the samples. The correlations are the most remarkable for the 10 μm band. As the SiO2 content decreases, the peak wavelengthλ m shifts to longer side, the peak heightK m decreases and the full width of half maximumW increases. A quantityλ m K m W is constant within 15%. Empirical formula $$\lambda_m (\mu m) = {11.10-2.30 x 10^-2} {[SiO_2 wt.\%]} \pm 0.15$$ and $$W(\mu m) = {5.14-4.68 x 10^- 2} {[SiO_2 wt.\%]} \pm 0.30$$ are obtained for the measured samples. Therefore, the correlation is present between the 10 μm peak wavelengthλ m and peak widthW for amorphous silicates. The change in peak widthW is remarkable compared the change in peak wavelengthλ m as the SiO2 content varies. For the 12 μm band the correlations with the SiO2 content are not so good. A tendency that theλ m shifts to the red and theK m lowers as the decreasing SiO2 content are found. For the samples with SiO2 content less than 50% the 12 μm band cannot recognized as the peak. For the 20 μm band, theλ m is almost independent on SiO2 content and theK m lowers with decreasing SiO2 content. The results are compared with the observed 10 μm band of the astronomical objects. A method to estimate the SiO2 content of astronomical grain materials is proposed and 48±8% SiO2 wt.% is found corresponding to the peak wavelength of 9.7 μm and the peak width of 2.5–3.0 μm of typical celestial objects.  相似文献   

8.
In the set of small satellites of Saturn recently imaged by the Voyager probes, we can observe the transition from irregularly-shaped, strength-dominated objects to larger, gravity-dominated bodies with shapes roughly fitting the theoretical equilibrium figures. The transition occurs for a radius of 100±50 km, corresponding to a typical material strength of the order of 107 dynes cm?2. We discuss briefly the cases of Mimas, Enceladus, Hyperion, Phoebe and the small coorbital and F-ring shepherding moons, showing that an analysis of the shape data can often provide interesting results on the physical properties, origin and collisional history of these objects.  相似文献   

9.
This paper describes the detailed calibration at soft X-ray energies (0.1–2.0 keV; 125 Å-6 Å) of gold coated, paraboloidal X-ray mirrors, four of which were subsequently flow on the Ariel-6 satellite. Uncertainties in the attitude of the satellite together with an apparent reduction in sensitivity of the soft X-ray experiment necessitated observations using the Crab Nebula as a reference. These showed that a dramatic reduction in the reflection efficiencies of all four mirrors had occurred, almost certainly after or during launch. An initial recalibration of the mirrors using the Crab observation is described.  相似文献   

10.
In this paper, the presence of Faraday rotation in measurements of the orientation of a sunspot's transverse magnetic field is investigated. Using observations obtained with the Marshall Space Flight Center's (MSFC) vector magnetograph, the derived vector magnetic field of a simple, symmetric sunspot is used to calculate the degree of Faraday rotation in the azimuth of the transverse field as a function of wavelength from analytical expressions for the Stokes parameters. These results are then compared with the observed rotation of the field's azimuth which is derived from observations at different wavelengths within the Fei 5250 Å spectral line. From these comparisons, we find: the observed rotation of the azimuth is simulated to a reasonable degree by the theoretical formulations if the line-formation parameter η o is varied over the sunspot; these variations in η o are substantiated by the line-intensity data; for the MSFC system, Faraday rotation can be neglected for field strengths less than 1800 G and field inclinations greater than 45°; to minimize the effects of Faraday rotation in sunspot umbrae, MSFC magnetograph measurements must be made in the far wings of the Zeeman-sensitive spectral line.  相似文献   

11.
The jet/grain model proposed by Ramatyet al. (1984, hereafter abbreviated as RKL) for production of the narrow gamma-ray lines reported from SS433 is examined and shown to be untenable on numerous grounds. Most importantly:
  1. The huge Coulomb collisional losses (W c?2×1041 erg s?1) from the jet, which would necessarily accompany non-thermal production of the gamma rays, demands a jet acceleration/collimation process acting over a very long range and with a power at least 102 times the Eddington limit for any stellar object.
  2. There is a collisional thick target limit (irrespective of jet mass) to the gamma ray yield per interstellar proton. Consequently, the gamma-ray data demand an improbably high interstellar density (?109 cm?3).
  3. For the grains to be kept cool enough (?3000 K) to survive the heating rateW c either by radiation or jet expansion would demand a ‘jet’ wider than its length and so inconsistent with narrow lines. In the case of radiative cooling, the resultant IR flux would exceed the observed values by a factor ?104.
  4. Light scattered on the jet grain mass required would be highly polarized, contrary to observations, unless the jet was optically thick to grains, again precluding their radiative cooling.
  5. To avoid unacceptable precessional broadening of the gamma-ray lines demands an emitting jet length ?0.5 days atv=0.26c. This increases the necessary mass loss rate by a factor ?10 over the values obtained by RKL who assumed a 4-day ‘flare’.
  6. The model also predicts rest energy gamma-ray lines which are not observed.
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12.
The observations of VV Ori inUBV and inuvby obtained by Chambliss in 1975–79 have been re-analyzed with the use of an updated version of the WINK program of Wood. Several solutions were obtained using the normal points (ca. 80 per light curve). These establish fairly reliable values for the linear limb-darkening coefficient of VV Ori A and approximate values for the luminosity of the third component of this system. Attempts to determine non-linear coefficients of limb darkening for the primary component, however, proved to be unsuccessful. Solutions were also obtained using all observations (ca. 620 per light curve). Very close agreement was found between the values of the geometric elements determined from these solutions and those determined by use of the normal points only. The solutions based on all observations produced reliable values foru 1, the limb darkening coefficient of VV Ori A, (typically, 0.30±-0.04). These results are in good agreement with theoretical limb darkening coefficients derived from model atmospheres calculations. The contribution of VV Ori C to the light of the system was also ascertained, and it was found that this could be best interpreted, if this component has a spectral type of A3V. The other orbital elements of VV Ori were also discussed, and the differences between the various solutions were noted. Since VV Ori A is one of the very few early-type stars for which reliable limb-darkening coefficients can be empirically determined, this system is viewed as being of considerable importance.  相似文献   

13.
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14.
We present the results of spectroscopic and photometric observations for three hot southern-hemisphere post-AGB objects, Hen 3-1347 = IRAS 17074-1845, Hen 3-1428 = IRAS 17311-4924, and LSS 4634 = IRAS 18023-3409. In the spectrograms taken with the 1.9-m telescope of the South African Astronomical Observatory (SAAO) in 2012, we have measured the equivalent widths of the most prominent spectral lines. Comparison of the new data with those published previously points to a change in the spectra of Hen 3-1428 and LSS 4634 in the last 20 years. Based on ASAS data, we have detected rapid photometric variability in all three stars with an amplitude up to 0 · m 3-0 · m 4 in the V band. A similarity between the patterns of variability for the sample stars and other hot protoplanetary nebulae is pointed out. We present the results of UBV observations for Hen 3-1347, according to which the star undergoes rapid irregular brightness variations with maximum amplitudes ΔV = 0 · m 25, ΔB = 0 · m 25, and ΔU = 0 · m 30 and shows color-magnitude correlations. Based on archival data, we have traced the photometric history of the stars over more than 100 years. Hen 3-1347 and LSS 4634 have exhibited a significant fading on a long time scale. The revealed brightness and spectrum variations in the stars, along with evidence for their enhanced mass, may be indicative of their rapid post-AGB evolution.  相似文献   

15.
On July 5, 1980 the Hard X-Ray Imaging Spectrometer on board the Solar Maximum Mission observed a complex flare event starting at 22 : 32 UT from AR 2559 (Hale 16955), then at N 28 W 29, which developed finally into a 2-ribbon flare. In this paper we compare the X-ray images with Hα photographs taken at the Big Bear Solar Observatory and identify the site of the most energetic flare phenomena. During the early phases of the event the hard X-rays (>16 keV) came from a compact source located near one of the two bright Hα kernels; we believe the latter are at the footpoints of a compact magnetic loop. The kernel identified with the X-ray source is immediately adjacent to one of the principal sunspots and in fact appears to ‘rotate’ around the sunspot over 90° in the early phase of the flare. Two intense X-ray bursts occur at the site of the rotating kernel, and following each burst the loop fills with hot, X-ray emitting plasma. If the first burst is interpreted as bremsstrahlung from a beam of electrons impinging on a collisionally dominated medium, the energy in such electrons, >16 keV, is ～ 5 × 1030 erg. The altitude of the looptop is 7–10 × 103 km. The temperature structure of the flare is extremely non-homogeneous, and the highest temperatures are found in the top of the loop. A few minutes after the hard X-ray bursts the configuration of the region changes; some of the flare energy is transferred along a system of larger loops that now become the defining structure for a 2-ribbon flare, which is how the flare develops as seen in Hα. In the late, cooling phase of the flare 15 min after maximum, we find a significant component of the plasma at temperatures between 25 and 30 × 106 K.  相似文献   

16.
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17.
John A. Eddy 《Solar physics》1983,89(1):195-207
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18.
The paper describes a new sensor for the spatial registration and measurement of particle parameters in near and deep space. The following modern materials are applied in the sensor structure: a PVDF piezoactive film and lightweight heat-shielding high-temperature aerogel. The results from studying the aerogel morphology as well as its thermal conductivity depending on the air temperature are presented. The thermal conductivity of a SiO2-aerogel is compared with one of foreign aerogels and air. Its elemental quantitative chemical composition is determined.  相似文献   

19.
L. Mollwo 《Solar physics》1983,83(2):305-320
The earlier interpretation of the Zebra patterns by the concept of double resonance is examined for a realistic magneto-hydrostatic model of a coronal condensation over a bipolar spot group. It appears that the frequency drift of the Zebra stripes over a longer time can scarcely be explained by a change of state of the plasma as done till now. The proposed modified mechanism is based on a helical beam of electrons forming fronts that excite radiation at places of double resonance. Considering the field and density configuration conditions are found which produce drifting Zebra stripes. Structures of longer duration and absorptions arise from more or less overlapping stripe segments, which are excited by the fronts following one another in a beam of sufficient great length. The second stripe system of other drift direction found by Slottje (1972a) arises from lateral splitting of the beam.  相似文献   

20.
Pioneer VI was launched into a circumsolar orbit on December 16, 1965, and was occulted by the sun in the latter half of November, 1968. During the occultation period, the 2292-MHz S-band telemetry carrier underwent Faraday rotation due to the interaction of this signal with the plasma and magnetic field in the solar corona. The NASA/JPL 210-ft diameter antenna of the Deep Space Network near Barstow, California, was used for the measurement. The antenna feed was modified for automatic polarization tracking for this experiment. The measurement results are interpreted with a theoretical model of the solar corona. This model consists of a modified Allen-Baumbach electron density and a coronal magnetic field calculated both from Mount Wilson magnetograph observations using a source surface model and field extrapolations from the Explorer 33 satellite magnetometer. The observations and the calculated rotation show general agreement with respect to magnitude, sense, and timing, suggesting the source-surface model and field extrapolations from 1 AU are a valid technique to obtain the magnetic field in the corona from 4 to 12 solar radii. Variations present can easily be ascribed to density enhancements known to be present in the corona. Longitudinal variations of the density in the corona cannot be obtained from coronagraph observations, and thus a purely radial variation was assumed. An improved fit to the Faraday rotation data is obtained with an equatorial electron density $$N = 10^8 \left( {\frac{{6000}}{{R^{10} }} + \frac{{0.002}}{{R^2 }}} \right)...{\text{ cm}}^{{\text{ - 3}}} {\text{ (4 < }}R < 12){\text{ }}...$$ where R is in solar radii. The work of W. V. T. Rusch and J. E. Ohlson was supported in part by research sponsored by the Joint Services Electronics Program through the Air Force Office of Scientific Research under Grant AF-AFOSR 69-1622A at the University of Southern California. The work done by K. H. Schatten was in part supported by the National Academy of Science on a National Research Council postdoctoral fellowship. The work of J. M. Wilcox was supported in part by the Office of Naval Research under Contract Nonr 3656(26), by the National Aeronautics and Space Administration under Grant NGR 05-003-230, and by the National Science Foundation under Grant GA-1319 at the University of California at Berkeley.  相似文献   

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