Showing papers on "Solar eclipse published in 1994"
TL;DR: In this article, the authors performed an exhaustive search of the astronomical literature to find all existing observations of solar eclipses suitable for this purpose, and also taken new observations by new techniques.
Abstract: The diameter of the Sun may be measured at the time of a solar eclipse. We have performed an exhaustive search of the astronomical literature to find all existing observations of solar eclipses suitable for this purpose. We have also taken new observations by new techniques. We have undertaken a project to reduce them systematically, and in an automated, self-consistent way. This will produce determinations of the solar radius at the times of solar eclipses from 1715 to the present. Re-reduction, using newer ephemerides, of observations made in 1984 shows that the component of the residuals caused by the ephemeris is substantially reduced. This paper summarizes the research plan, outlines the detailed astronomical features included in the calculations, and presents the results available.
26 citations
TL;DR: In l'epoque d'Hipparque, Thales predit cet extraordinaire evenement, l'un des plus celebres de l'histoire grecque.
Abstract: Il avait ete demontre qu'aucune prediction d'eclipse solaire ne pouvait etre possible avant l'epoque d'Hipparque. Pourtant, quatre siecles auparavant, Thales predit cet extraordinaire evenement, l'un des plus celebres de l'histoire grecque
20 citations
TL;DR: The fine structure of the solar limb in coronal holes was explored at temperatures ranging from 10(exp 4) to 10 (exp 6) K as mentioned in this paper, where the brightness of these structures changes as a function of height above the limb.
Abstract: The fine structure of the solar limb in coronal holes is explored at temperatures ranging from 10(exp 4) to 10(exp 6) K. An image enhancement algorithm orignally developed for solar eclipse observations is applied to a number of simultaneous multiwavelength observations made with the Harvard Extreme Ultraviolet Spectrometer experiment on Skylab. The enhanced images reveal the presence of filamentary structures above the limb with a characteristic separation of approximately 10 to 15 sec . Some of the structures extend from the solar limb into the corona to at least 4 min above the solar limb. The brightness of these structures changes as a function of height above the limb. The brightest emission is associated with spiculelike structures in the proximity of the limb. The emission characteristic of high-temperature plasma is not cospatial with the emission at lower temperatures, indicating the presence of different temperature plasmas in the field of view.
18 citations
TL;DR: In this paper, the authors recorded shadow bands just before and just after the total phase of the solar eclipse of 11 July 1991, using two broad band silicon photodiodes separated horizontally by 100 mm, near to where the eclipsed Sun lay as seen from their observing site close to San Jose del Cabo in Baja California.
11 citations
Book•
01 Jan 1994
TL;DR: In this article, the authors present a detailed analysis of the 1991 total solar eclipse and its effect on the spectrum of the visible spectrum of infrared light, including magnetic fields and line formation.
Abstract: Preface. Foreword. 1. Infrared Diagnostics of the Solar Atmosphere and Solar Activity. 2. Infrared Observations of the 1991 Total Solar Eclipse. 3. Infrared Perspectives on Atmospheric Dynamics. 4. Infrared Atomic Physics and Line Formation. 5. Magnetic Fields and Infrared Magnetometry. 6. The Infrared Spectrum. 7. Infrared Technology and the Future.
11 citations
TL;DR: In this paper, the ground-based density measurements will be complimentary to SOHO observations, particularly SohO electron density measurements, and recent observations from NSO/Sac Peak are discussed.
Abstract: Observations made during the 1991 total solar eclipse and recent observations from NSO/Sac Peak are discussed. The ground-based density measurements will be complimentary to SOHO observations, particularly SOHO electron density measurements.
5 citations
01 Apr 1994
TL;DR: In this article, the numerical modeling of the changes of the concentration of trace gases in the atmosphere during the eclipse shows that the NO2 total content in the vertical column increases approximately by 80 percent.
Abstract: The numerical modeling of the changes of the concentration of trace gases in the atmosphere during the eclipse shows that the NO2 total content in the vertical column increases approximately by 80 percent. The first observations of the NO2 total content during the eclipse of 1981 have given 60 plus or minus 20 percent. In the observations of 1990 the more precise methods and instruments for stratospheric NO2 measurements were used. The surface ozone, NO, and NO2 concentrations were under control. The results of the observations give the increasing of the stratospheric NO2 during the eclipse by 55 plus or minus 6 percent. The maximum increasing of the NO2 content is observed at the moment of the maximum phase.
4 citations
TL;DR: The morning twilight of the presunrise sky was measured at the Hoher-List Observatory during the total eclipse of 22 July 1990 and the luminance showed a deep minimum in twilight during the main phase of the solar eclipse compared with normal conditions.
Abstract: The morning twilight of the presunrise sky was measured at the Hoher-List Observatory during the total eclipse of 22 July 1990. The location of observation was far away from the central eclipse zone. The luminance showed a deep minimum in twilight during the main phase of the solar eclipse compared with normal conditions. A first order scattering model explains the observations reasonably well and shows that the sky radiation during the first phase of twilight at a location far away from the central umbra depends primarily on the height profile of the air pressure between ~ 100 and 200 km.
4 citations
01 Jan 1994
TL;DR: In this article, a narrow band filter at wavelength 2.12 µm was used to observe the solar corona during the total solar eclipse of 11 July 1991, and compared with results obtained by two observers during the eclipse of November 1966, and shortly thereafter.
Abstract: Observations of the solar corona in a narrow band filter at wavelength 2.12 µm during the total solar eclipse of 11 July 1991 are described, and compared with results obtained by two observers during the eclipse of November 1966, and shortly thereafter. The lack of any observable. signature of thermal emission in the 1991 results suggests that during 1966/67, the near-solar environs were subjected to a locally enhanced dust population, supplied by one or more sungrazer comets. Possible conditions which match the observational circumstances are discussed.
4 citations
01 Jan 1994
TL;DR: In this article, a 3.8-cm, f/2 objective was used to search for dust or rocky rings around the Sun, previously detected at about 4 R ⊙.
Abstract: Infrared images (1.65 μm) of the eclipsed Sun were taken atop Mauna Kea, Hawaii, during the July 11, 1991 total eclipse with an Amber Engineering 128 × 128 InSb array camera. The camera, mounted on a portable solar tracker, had a 3.8-cm, f/2 objective that produced a 4.9° field of view. The primary objective of the experiment was to search for dust or rocky rings around the Sun, previously detected at about 4 R ⊙. High thin clouds, atmospheric dust and aerosols from the June 1991 explosion of Mount Pinatubo in the Philippines, and the overall brightness of the solar corona resulted in a very high infrared background. Despite this, high signal-to-noise radial infrared intensity profiles were obtained of the solar corona from the Moon’s limb out to about 10 R ⊙. Preliminary analysis shows some evidence for an enhanced surface brightness between 3 to 4 R ⊙along the east-west direction, but much fainter than seen in previous solar eclipses. The transition region between the K-corona and the F-corona clearly shows at 2.5 R ⊙, and the surface brightness of the F-corona as a function of radius (from about 2 to 10 R ⊙) can be fit by a simple power law.
4 citations
TL;DR: In this article, the authors observed the linear polarization of the solar corona in the white light and in the green emission line 530.3 nm during the 1991 total solar eclipse (La Paz, Mexico).
01 Jan 1994
TL;DR: The solar corona on July 11, 1991 had a shape unusual in terms of standard picture for the time near the sunspot maximum as mentioned in this paper, which confirmed the concept of the flat solar coronal streamer belt with the heliospheric current sheet.
01 Jan 1994
TL;DR: In this paper, the authors present observations of the 11 July 1991 total solar eclipse made from the Caltech Submillimeter Observatory, where the 850 µm limb is extended 3380±140 km above the visible limb, and there is a 10% brightening at the extreme limb.
Abstract: We present observations of the 11 July 1991 total solar eclipse made from the Caltech Submillimeter Observatory. The 850 µm limb is extended 3380±140 km above the visible limb, and there is a 10% brightening at the extreme limb. The measured limb height agrees with previous work at shorter and longer wavelengths. The run of limb heights with wavelength is well fit by a single electron density scale height. We argue that there is no need to invoke spicule geometry to explain the observations.
01 Jan 1994
TL;DR: In this paper, the authors used the NASA 3-meter Infrared Telescope Facility and a new Goddard large cryogenic grating spectrometer to study the limb profile of the 1232 µm MgI emission line.
Abstract: The 11 July 1991 total solar eclipse over Mauna Kea was a unique opportunity to study the limb profile of the 1232 µm MgI emission line Our observations used the NASA 3-meter Infrared Telescope Facility,1 and a new Goddard large cryogenic grating spectrometer Spectra of the line were taken in the slitless mode at second contact The results show that the emission peaks within ~ 300 km of the 12-µm continuum limb This agrees with recent theoretical predictions for this line as a NLTE upper photospheric emission feature However, the increase in optical depth for this extreme limb-viewing situation means that most of the observed emission arises from aboveT min,and we find that this emission is extended to altitudes well in excess of the model predictions The line emission can be traced to altitudes as high as 2000 km above the 12-µm continuum limb, whereas theory predicts it to remain observable no higher than 500 km above the continuum limb The substantial limb-extension observed in this line is qualitatively consistent with limb-extensions seen by other observers in the far-IR continuum, and may be indicative of departures from gravitational hydrostatic equilibrium in the upper solar atmosphere, and/or may result from temperature and density inhomogeneities The extended altitude of formation of this line enhances its value as a Zeeman probe of magnetic fields
01 Jan 1994
01 Jan 1994
TL;DR: In this paper, the authors propose to reduce the chronological data of a narrative source describing a historical fact to modern dating units, i.e., be referred to by B.C. or A.D.
Abstract: Chronology informs us of how much time has passed since a certain historical fact. Meanwhile, the chronological data of a narrative source describing the fact should be reduced to the modern dating units, i.e., be referred to by B.C. or A.D. This problem proves to be quite complicated, since many a historical inference depends on which date we ascribe to the events discussed in the source.
01 Jan 1994
TL;DR: In this article, the thermal structure of the corona was studied in the light of the He I 10830 A line, the 10000 A continuum, and the Fe XIV 5303 A line.
Abstract: Coronal images were taken in the light of the He I 10830 A line, the 10000 A continuum, and the Fe XIV 5303 A line, with the aim of studying the thermal structure of the corona. In addition, spectroscopic observations were made in the violet wavelength region (3760-4060 A) and near-infrared (10745-10835 A), to obtain details of physical conditions of the corona, especially of its cool part. The data obtained do not show any distinct cool structures other than ordinary prominences. Some preliminary results concerning the corona and prominence structures are given.
01 Jul 1994
TL;DR: A total eclipse of the sun will be visible from Asia and the Pacific Ocean on 24 Oct. 1995 as mentioned in this paper, where the path of the moon's shadow begins in the Middle East and sweeps across India, Southeast Asia, and the waters of the Indonesian archipelago before ending at sunset in the Pacific.
Abstract: A total eclipse of the sun will be visible from Asia and the Pacific Ocean on 24 Oct. 1995. The path of the moon's shadow begins in the Middle East and sweeps across India, Southeast Asia, and the waters of the Indonesian archipelago before ending at sunset in the Pacific. Detailed predictions for this event are presented and include besselian elements, geographic coordinates of the path of totality, physical ephemeris of the umbra, topocentric limb profile corrections, local circumstances for 400 cities, maps of the eclipse path, weather prospects, the lunar limb profile, and the sky during totality.
Patent•
20 Jul 1994
TL;DR: In this paper, the authors propose a tridimensional teaching aid simulating celestial body movements which mainly comprises a triangular supporting frame, a rotary frame, dynamic force source, a metric dial, a parallel light source, an sun, a moon, an earth, a time difference dial and a lunar dial.
Abstract: The utility model relates to a tridimensional teaching aid simulating celestial body movements which mainly comprises a triangular supporting frame, a rotary frame, a dynamic force source, a metric dial, a parallel light source, a sun, a moon, an earth, a time difference dial and a lunar dial. The utility model can exactly demonstrate the running traces of the sun, the earth and the moon and lunar or solar calendar times corresponding to the positions of the sun, the earth and the moon. When the running positions of the earth, the sun and the moon conform to a certain condition, the utility model can display the total lunar eclipse, the partial lunar eclipse and the partial solar eclipse. The utility model has the advantages of simple structure, reliable performance, high precision of running and objective demonstration. The utility model is an objective tridimensional teaching aid and can be made into a fine tridimensional calendar.
Posted Content•
TL;DR: In this paper, a pedagogical review of neutrino oscillations including vacuum oscillations, constant density matter oscillations and variable density mass oscillations is presented, and the question of whether MSW solar neutrinos oscillations in the moon could be observed during a solar eclipse is addressed.
Abstract: The first three quarters of this paper consists of a pedagogical review of neutrino oscillations, including vacuum oscillations, constant density matter oscillations and variable density matter oscillations. We then address the question of whether MSW solar neutrino oscillations in the moon could be observed during a solar eclipse. For the small angle MSW solution, the effect is unmeasureable; for the large angle solution, we find an enhancement in the rate which can be as large as a factor of two. Since the center of the Sun, as seen from a typical solar neutrino detector (through a transparent Earth) is covered for roughly three hours per decade, a world-wide event rate of a few solar neutrino events per hour might be sufficient to observe this effect. This work constituted the undergraduate senior thesis of Brian Mason, and has been submitted to the American Journal of Physics.
01 Jan 1994
TL;DR: In this article, near IR total eclipse measurements have provided clear evidence during both 2nd and 3rd contacts for a limb extension of about 125 km for wavelengths in the range containing the CO fundamental vibration-rotation bands between 4.3 and 5.5 µm, when compared to the limb at nearby shorter wavelengths.
Abstract: Near IR total eclipse measurements have provided clear evidence during both 2nd and 3rd contacts for a limb extension of about 125 km for wavelengths in the range containing the CO fundamental vibration-rotation bands between 4.3 and 5.5 µm, when compared to the limb at nearby shorter wavelengths. This is interpreted as a “flash” spectrum in the CO lines, with the above extension representing the outer level of the CO emission layer. This height can be compared to the τco = 1.0 level incorporated into recent representative atmospheric models (Ayres and Wiedemann, 1989) which is 90 km above the visible limb for a semi-empirical “hot chromosphere” model (Avrett, 1985) and 220 km for a “cool” radiative equilibrium model based upon work by Anderson (1989).
01 Jan 1994
TL;DR: The total solar eclipse of July 11, 1991 was observed from La Matanza, Baja California Sur, Mexico, only 5 km south of the center line of totality, with several small instruments intended to obtain images of the corona during totality, and using a range of exposure times which allowed to detect both the inner and outer corona.
Abstract: The total solar eclipse of July 11, 1991 was observed from “La Matanza”, Baja California Sur, Mexico, only 5 km south of the center line of totality, with several small instruments intended to obtain images of the corona during totality, and using a range of exposure times which allowed us to detect both the inner and outer corona. Relations between large and fine scale structures of the corona, the photospheric and chromospheric activity, and the presence of coronal holes are presented.