Showing papers on "Solar eclipse published in 1974"

Faraday rotation studies in Africa during the solar eclipse of June 30, 1973

Abstract: FOUR stations were set up in southern and eastern Africa (Table 1) to observe variations of total electron content during the eclipse of the Sun on June 30, 1973. Each station was equipped with a conventional Faraday rotation recording system consisting of a receiver and a mechanically rotating aerial. We recorded the amplitude fading of the 137 MHz signals from the geostationary satellite, Intelsat IIF3, located at approximately 14°W. The four stations were operating for a total period of 10 d, including June 30, the day of the eclipse.

Hipparchus on the distances of the sun and moon

Abstract: "Hipparchus' investigation of this topic is based principally on the sun. For since it is a consequence of certain other properties of the sun and moon (which we shall discuss below) that when the distance of one of the luminaries is given that of the other is also determined, he tries to demonstrate the distance of the moon by guessing the distance of the sun. He first assumes that the sun has only the least perceptible parallax, in order to find its distance, and afterwards uses the solar eclipse which he adduces. At one time he assumes that the sun has no perceptible parallax, at another that it has a significant [ixavov] parallax : as a result the ratios of the moon's distance [to the earth's radius] came out different for him for each of the hypotheses he set out. For in the case of the sun it is quite uncertain not merely how great a parallax it has, but whether it has any at all".

The F1 region during a solar eclipse

Abstract: Temperature and ion composition results obtained during the eclipse of 7 March 1970 at Millstone Hill are presented. The temperature variations appear to be controlled by the high degree of magnetic activity present on the eclipse day. Ion composition variations may be explained in terms of photochemical processes and the distribution of ionizing radiation across the solar disk. The data indicate the quality of ion composition determination by incoherent scatter radar, and it is concluded that these data are more useful when averaged in quantity to determine diurnal, seasonal, and solar cycle variations rather than short-term temporal variations on a given day.

Electrons in the solar corona. I. Electron density models of streamers at eclipse 15 February 1961

Abstract: During the eclipse of 15 February 1961, photometric measurements were obtained for the inner corona till r/Ro = 2.5 at hnperia, Italy (Figure 1), and for the outer corona between r/Ro = 2.0 and 7.0 at Hvar, Jugoslavia (Plate I). Morphologic pictures of the streamers were taken at Observatoire de Haute-Provence, France, with the technique of the gradient compensation (Plate II). K-corona- meter observations were daily recorded at Meudon and Pic-du-Midi Observatories, France, from 9 to 22 February 1961 (Figures 9 and 10). These combined techniques give accurate localization, shape and photometry of the streamers. Four of them lie near the limb-plane and the mathematical approach of Van de Hulst applies to derive the electron-density repartition within these streamers (Figures 13, 15 and 16a). Compared with the pre- viously published electron-density determinations on 10 corona-streamers (Figure 16b), the new determinations correspond to a particularly large variety of streamers. Local increases of electron- densities are found at the neck of helmet-shaped streamers, with an almost local zero gradient and are discussed. A research program was initiated in the decade of the 50's by the Laboratory 'Physique du Syst6me Solaire', Observatoire de Paris, Meudon (France) to refine our knowledge about the electron densities and their variations in coronal streamers and condensa- tions. The electrons are detected by their Thompson scattering of the solar light in the optical range. Observational techniques were: the K-coronameter photoelectric polarimeter to survey the inner parts of the corona, the balloon-borne externally occulted corono- graph to study the streamers up to 5 solar radii from the center of the Sun, and the eclipse white light photometry. The present Part ( refers to the solar eclipse of 15 February 1961. Measurements of the number of electrons by cm 3 within 4 coronal streamers are given. Typical electron density models for coronal streamers are derived.

Partial solar eclipse effects on temperature and wind in an equatorial atmosphere

Abstract: A partial solar eclipse (approximately 3-hour duration) occurred at Fort Sherman, Panama Canal Zone (9°20′N, 79°59′W), in the early morning hours on December 24, 1973. Five rocket-borne temperature sensors were deployed at an altitude of 60–65 km before, during, and after the eclipse. Temperatures and winds were measured as the sensors descended by parachute. Analysis of the data indicates that there was 3°–5°C cooling produced in the 50- to 52-km layer as the solar radiation was partially blocked from reaching the earth's atmosphere. Zonal wind speed was also affected at those levels from 15 m/s before the eclipse to 9 m/s during the maximum phase.

Normal and abnormal E‐region electron density profiles at a midlatitude station

Abstract: The problems of measuring reliable E-region electron density vs. height profiles with a vertically pointing, pulsed incoherent scatter radar are discussed, and profiles from heights of 90 km upward observed at Malvern are presented. The minimum above h/.sub max/E is more pronounced in winter than in summer, and the overall average density in the minimum is 92% of N/sub max/E. From the observationai point of view profiles showing an unresolved sporadic-E layer seen merely to be an extreme case of the normal type. Many layers are present in the E region at night; the behavior of these is erratic except for the principal layer centered just below 100 km, which may be meteoritic in origin. Incoherent scatter offers a new method of investigating the effects of solar flares in the 100 to 130 km range; observations taken during a flare, and also during a partial solar eclipse and on a magnetically disturbed day, are described. (auth)

Internal Gravity-Wave Motions Induced in the Earth's Atmosphere by a Solar Eclipse

Abstract: In a solar eclipse, the moon shields a limited region of the earth's atmosphere from the heating effect of the solar radiation. This shadow travels through the earth's lower atmosphere at supersonic velocity, causing the neutral gas to emit internal gravity waves that form a bow wave about the shadow region. Tentative estimates of the amplitude of this wave indicate that it will be detectable well outside the area where the eclipse can be observed directly.

The continuum of the extreme limb and the chromosphere at the 1970 eclipse

Abstract: The flash spectra of the partial Sun and the chromosphere were obtained at the total solar eclipse on 7 March, 1970. We studied the distributions of the surface brightness of the continuum at six wavelengths in the visual region to compare them with the previous observations and the existing model atmospheres. All of the distributions show a shallow dip and a small hump similar to those of Heintze's observation at the 1954 eclipse. But the hump in our results is of quite a different type from that given by Heintze's revised model. It was found that none of the existing model atmospheres can reproduce this hump. The intensity distribution in the low chromosphere was also examined.

Atmospheric gravity waves induced by Earth's diurnal rotation

Abstract: Tentative arguments are drawn to suggest that portions of the earth's lower atmosphere in the course of the earth's diurnal rotation could behave in a manner analogous to the fast moving cooling spot of the lunar shadow during a solar eclipse and thereby could induce atmospheric gravity waves in that region. The implications of this phenomenon are qualitatively explored for describing some features of TID's and sporadic E in the ionosphere as have been reported elsewhere.

Photometrie photographique de la couronne solaire

Abstract: A series of plates of the solar corona were obtained during the total solar eclipse of July 10th, 1972 near Anadyr (U.S.S.R.) using a standard eclipse coronagraph of O = 20 cm and F = 300 cm. A neutral radial filter (Figure 2) was specially conceived to enable the study of the corona up to 5 R ⊙ and also that of the lunar background. The absolute calibration takes into consideration the different components of the recorded radiation: the K and F corona, the sky background B c, the coronal aureola B aur and details of the earthshine on the lunar background. The brightness of the corona (K + F) is given along the N-S and E-W axes and also the total brightness recorded along the tangential directions, at selected radial distances. The photometry shows that the K corona in 1972 was very heterogeneous and its mean brightness close to that of a corona of maximum activity for r < 2 R ⊙. Moreover, the difference of brightness between the equator and the poles for r > 2 R bd is about twice larger than in the Van de Hulst' model of the corona of minimum activity. At the north pole, a coronal ‘hole’ clearly appears.

The coronal aureola in the time of total solar eclipse

Abstract: A computational method allowing one to obtain the intensity of the coronal aureola from the measures of the solar aureola is proposed. The method is applied to 2 very different observations performed at the solar eclipses at Sept. 22, 1968 and March 7, 1970. In addition, a scattering function is given for some typical cases observed (clear sky) showing a large variety in values. Use of this type of function is suggested in order to describe the scattered light superimposed on the lunar earthshine and the sky background. For good observing conditions, it is shown that the coronal aureola is everywhere one order of magnitude less than the F-corona but becomes higher than the minimum electronic corona, for r > 2.5. When the sky background is important. especially because of the low value of the eclipse magnitude, the intensity of coronal aureola may be compared to the F-corona intensity. (auth)

Coronal disturbances : symposium no. 57 held at Surfers Paradise, Queensland, Australia, 7-11 September, 1973

Abstract: I / Magnetic Structure Responsible for Coronal Disturbances.- Magnetic Structure Responsible for Coronal Disturbances: Observations.- Magnetic Structure Responsible for Coronal Disturbances: Theory.- Inversion Lines of Photospheric Magnetic Fields and Solar Corona (Presented by M.-J. Martres).- Large-Scale Magnetic Structures Responsible for Coronal Disturbances (Presented by V. Bumba).- Distribution of Circularly Polarized Emission across the Solar Disk at ? = 4.3 cm (Presented by P. Kaufmann).- Boundary Fitting Problems Associated with Coronal Magnetic Models.- Analysis of EUV Observations of a Coronal Active Region Made During the 7 March 1970 Eclipse (Presented by C. Jordan).- Coronal Magnetic Field Structure Derived from Two-Frequency Radioheliograph Observations (Presented by K. V. Sheridan).- II / The Flash Phase of Solar Flares.- Impulsive (Flash) Phase of Solar Flares: Hard X-Ray, Microwave, EUV and Optical Observations.- Spectral Association of the 7 August 1972 Solar Radio Burst with Particle Acceleration (Presented by J. P. Castelli).- X-Ray Emission in Absence of Flares Related to H? Activity and Type III Burst Production (Presented by M.-J. Martres).- Coronal Disturbances Observed in the Optical Emission Lines.- Forbidden Line Excitation Data for Certain Coronal Lines (Presented by L. H. Aller).- Multiple Hard X-Ray Bursts and Associated Emission.- Ground-Based Observations of Type III Bursts.- Solar Radio Bursts at Low Frequencies.- The Flash of Solar Flares: Satellite Observations of Electrons.- High Resolution Studies of Type III Solar Radio Bursts (Presented by H. Rosenberg).- Coronal Density Structures in Regions of Type III Activity (Presented by Y. Leblanc).- Meter and Decameter Wavelength Positions of Solar Radio Bursts of July 31-August 7, 1972 (Presented by W. C. Erickson).- Source Structure in Metre-Wave Type V Solar Bursts (Presented by N. R. Labrum).- Direct Measurements of the Directivity of Type I and Type III Radiation at 169 MHz (Presented by C. Carou-balos).- Paired Type III Bursts (Presented by M. Pick).- Unusual Absorption of a Solar Type II Burst by `Shadow' Type III Bursts.- High Resolution Observations of Generalized Fast Drift Bursts (Presented by ?. Elgaroy).- Mechanisms for Flash Phase Phenomena in Solar Flares.- A Theory of Type III Solar Radio Bursts (Presented by D. B. Melrose).- A Relationship Between the Brightness Temperatures for Type III Bursts.- The Third Harmonic in Solar Radio Bursts (Presented by D. B. Melrose).- Fine Structure in Type IV Solar Radio Bursts (Presented by H. Rosenberg).- A Theory of Type I Solar Radio Bursts.- Synchrotron Radiation in Directions Close to Magnetic-Field Lines.- III / Shock Waves and Plasma Ejection.- Shock Waves and the Ejection of Matter from the Sun: Radio Evidence.- Optical Evidence for Plasma Ejections and Waves in the Solar Corona.- The Behaviour of the Outer Solar Corona (3 R? to 10 R?) During a Large Solar Flare Observed from OSO-7 in White Light.- The Coronal Disturbance of 12 August 1972 (Presented by A. C. Riddle).- Observation of a Coronal Disturbance from 1 to 9 R? (Presented by R. T. Stewart).- Type II Solar Radio Bursts in the Decimeter Band.- Observations of Split-Band Harmonic Type II Bursts with the Culgoora Radioheliograph at 80 and 160 MHz (Presented by G. J. Nelson).- Type II Bursts at Hectometric and Kilometric Wavelengths from Interplanetary Shocks (Presented by H. H. Malitson).- East-West Asymmetry on Magnetic Bottle Expansion and Its Relation to Shock Waves Propagating in the Solar Atmosphere.- Shock Waves and Plasma Ejection: Corpuscular and Interplanetary Evidence (Presented by G. Newkirk).- Theory of Shock Waves and Plasma Wave-Emission.- Interplanetary Shock Waves from McMath Region 11976 During Its Passage in August 1972 (Presented by M. Dryer).- Type II Burst-Sources as Low-VA Regions in the Corona `Illuminated' by Flare-Induced MHD Shocks.- On the Theory of Moving Type IV Radio Bursts.- On Split-Band Structure in Type II Radio Bursts from the Sun (Presented by S. F. Smerd).- On the Thermal Interpretation of Hard X-Ray Bursts from Solar Flares.- IV / Acceleration, Containement and Emission of High-Energy Flare Particles.- The Charge and Isotopic Composition of Solar Cosmic Rays.- X-Ray Evidence for the Acceleration, Containment, and Emission of High Energy Flare Particles.- Acceleration, Containment and Emission of High Energy Flare Particles: Radio Evidence.- Particle Acceleration in Solar Flares.- Millimeter Radio Evidence for Containment Mechanisms in Solar Flares (Presented by E. B. Mayfield).- Acceleration, Containment, and Emission of Very Low Energy Solar Flare Particles (Presented by R. P. Lin).- Solar Radio Pulsations.- Coronal Magnetic Fields and Energetic Particles.- Coherent Effect in the Preferential Acceleration of Relativists Solar Heavy Cosmic Ray Nuclei.- A Conductive Cooling Model for a Confined Solar Flare Plasma (Presented by L. W. Acton).- The Gyro-Synchrotron Radiation from Moving Type IV Sources in the Solar Corona.- V / Reports on Special Observatoins.- Temporal Observations of the ? 5303 Emission Line Profile During the 74 Minute Totality from the Concorde SST at the 30 June 1973 Total Solar Eclipse: Preliminary Intensity Variations Above an Active Region (Presented by D. H. Liebenberg).- Skylab: A Progress Report (Presented by G. Newkirk).- Preliminary Results from the NRL/ATM Instruments from Skylab SL/2.- Solar EUV Photoelectric Observations from Skylab.- Dynamic Events in the X-Ray Corona (A Progress Report from the AS&E X-Ray Telescope on Skylab).- The High Altitude Observatory White Light Coronagraph Experiment.- Index of Subjects.

Temporal Observations of the λ 5303 Emission Line Profile during the 74 Minute Totality from the Concorde SST at the 30 June 1973 Total Solar Eclipse: Preliminary Intensity Variations Above an Active Region

Abstract: (Nature). Apparatus was flown aboard the French-British Concorde SST to obtain high resolution emission line intensity profiles during the 30 June 1973 total solar eclipse. A prime objective was to obtain profiles that could be used to determine the presence in the FeXIV coronal emission line, 530.3 nm, of the 300 s periodicity such as is observed in the photosphere and chromosphere. The long totality duration of 74 min on the French Concorde 001 provided a unique opportunity for this study. At the 55000 ft cruise altitude weather influences are negligible, scattered light background reduced and seeing conditions excellent. The instrumentation included a high resolution pressure scanned Fabry-Perot interferometer and high resolution recordind. This instrumentation was perfected in earlier Los Alamos Scientific Laboratory solar eclipse flights since 1965 (Liebenberg, 1965, 1967; Hoffman et al., 1970). A 12 cm aperture window and 7.7 cm aperture f/13 telescope were designed to optimize the use of the available space as shown in Figure 1.

Spectral irradiance curve calculations for any type of solar eclipse

Abstract: A simple procedure is described for calculating the eclipse function (EF), alpha, and hence the spectral irradiance curve (SIC), (1-alpha), for any type of solar eclipse: namely, the occultation (partial/total) eclipse and the transit (partial/annular) eclipse. The SIC (or the EF) gives the variation of the amount (or the loss) of solar radiation of a given wavelength reaching a distant observer for various positions of the moon across the sun. The scheme is based on the theory of light curves of eclipsing binaries, the results of which are tabulated in Merrill's Tables, and is valid for all wavelengths for which the solar limb-darkening obeys the cosine law: J = sub c (1 - X + X cost gamma). As an example of computing the SIC for an occultation eclipse which may be total, the calculations for the March 7, 1970, eclipse are described in detail.

Curvature and surface distribution of the polar rays in the solar corona on 12 November 1966

Abstract: Following a technique developed by Saito, the positions and orientations of the polar rays visible in a photograph of the total solar eclipse of 12 November 1966 were examined to infer the length of an equivalent bar magnet representing the Sun's external magnetic field and the true distribution of polar rays from the two-dimensional projection seen in the photograph. In spite of the strong asymmetry in solar activity between the northern and southern solar hemispheres at the time of the eclipse, it was found that the magnetic field as delineated by the polar rays could be well represented by an extended dipole whose poles were each 0.43 R ⊙ from the center of the Sun and on the axis of rotation. The polar rays are distributed mainly in a circular zone 9° away from the pole and about 8° wide, with this zone bounded by empty regions at the pole and 15° to 20° away from it, beyond which there are again some rays, but not so many. These results are in good accord with expectation from Saito's analysis.