Observations Of Solar Eclipse Research Articles

Halley as an eclipse pioneer: his maps and observations of the total solar eclipses of 1715 and 1724

Total solar eclipses crossed England in 1715 and 1724, and Edmond Halley took advantage of the occasions to make broadside maps in order to solicit observations and to summarize the results. His articles in <italic>Philosophical Transactions of the Royal Society</italic> turn out to represent early references to phenomena usually associated with later observers. This article describes reports and maps by Halley and by other scientists of the time, including William Whiston. The Houghton Library of Harvard University and the Royal Astronomical Society of London, between them, own copies of all these maps. The maps drawn by Halley and Whiston for the 1724 eclipse are surprisingly similar to a modern map drawn for the 1999 August 11 total solar eclipse.

Historical eclipses and the rotation of the earth

This paper summarises recent research on long-term variations in the Earth's past rotation. A variety of ancient and medieval observations of both solar and lunar eclipses are investigated to determine changes in the length of the day (LOD) between 700 BC and AD 1600. These data originate from Babylon, China, Europe and the Arab world. In all, some 400 individual observations - both timed and untimed - are analysed. The results indicate an average rate of increase in the LOD by 1.7 milliseconds per century (ms/cy), considerably less than that calculated on the basis of lunar and solar tidal friction alone (i.e. 2.3 ± 0.1 ms/cy). The residual mean non-tidal decrease in the LOD by about 0.6 ms/cy is in good accord with that expected on the basis of post-glacial isostatic compensation. However, there is also some indication of long-term fluctuations in the LOD of amplitude some 4 ms on a time-scale of around 1500 years. Possible causes are core-mantle coupling and variations in global sea-level associated with climatic fluctuations.

Records of lunar eclipses in medieval Arabic chronicles

In a previous paper, we discussed a series of solar eclipse observations recorded in medieval Arabic chronicles both for their astronomical and chronological value. In the present paper we investigate lunar eclipses reported in these same sources as well as in many further chronicles. It should be stressed that our interest here is limited to eclipse records from chronicles; we have not included any material from technical treatises composed by astronomers. The observations are largely from al-Andalus (Islamic Spain), Egypt, Iraq, and Syria; they mainly cover the date range from A.D. 867 to 1520, with additions from 1674 to 1791.

日食観測の学術的意義と今後の課題

日食観測の学術的意義と今後の課題

Radio observations of total solar eclipse of November 3, 1994 at Chapecó (Brzil)

Radio observations of the eclipse on November 3, 1994, were carried out at Chapecó, Brazil by using a decimetric spectrograph having high spectral and time resolution. The light curve shows that: (1) Time variation of the radio flux before the totality was more compared to that after. (2) During the totality radio emission at 1.5 GHz was observed. Advantage of high spatial resolution (∼ 3.2 arc sec) possible during solar eclipse enabled us to determine the height of radio emission at 1.5 GHz. (3) Microwave bursts were observed associated with metric Type III-RS bursts. The source size of one of the microwave bursts was ∼ 7 arc sec and its physical parameters have been estimated. (4) The time difference between radio and optical contacts suggested for the first time asymmetrical limb brightening at 1.5 GHz.

An analysis of POAM II solar occultation observations of polar mesospheric clouds in the southern hemisphere

The second Polar Ozone and Aerosol Measurement (POAM II) instrument is a space‐borne visible/near IR photometer which uses the solar occultation technique to measure vertical profiles of ozone, nitrogen dioxide, and water vapor as well as aerosol extinction and atmospheric temperature in the stratosphere and upper troposphere. Here we report on the detection of polar mesospheric clouds (PMCs) in the high‐latitude southern hemisphere by POAM II during the 1993 and 1994 summer seasons. These measurements are noteworthy because they are the first measurements of PMCs in atmospheric extinction. The POAM II PMC data set has been analyzed using a simple geometric cloud model. We find that mean cloud altitudes deduced from these data are 82–83 km, consistent with previous ground‐based and satellite measurements. In addition, the 0.7 km vertical resolution of POAM II allows for accurate determination of cloud thickness. For the PMCs detected by POAM II we find a mean thickness of 2.4 km. The mean peak slant optical depth was determined to be 1.2×10−3 for the 1993 season and 1.8×10−3 for the 1994 season, corresponding to a cloud extinction coefficient of 3.9×10−6 and 6.1×10−6 km−1, respectively. The multichannel capability of POAM II also makes it possible to study the wavelength dependence of the measured slant optical depth for the clouds with largest extinction. The results of this analysis suggest an upper limit to the modal particle radii for these clouds of approximately 70 nm.

A comparison of ozone measurements made by the ATMOS, MAS, and SSBUV instruments during ATLAS 1, 2, and 3

Ozone profile measurements were made by three instruments, ATMOS, MAS, and SSBUV, using distinctly different observing techniques, as part of the ATLAS Space Shuttle missions in March 1992, April 1993, and November 1994. ATMOS makes solar‐occultation observations of infrared spectra using a Fourier transform interferometer. MAS uses a limb‐scanning antenna to measure emission spectra at millimeter wavelengths. SSBUV is a nadir‐viewing instrument measuring the transmission of scattered solar ultraviolet radiation modified by ozone absorption. A sample of zonal‐mean mixing ratio profiles indicates that these three ATLAS instruments generally agree to within 10%, although a few potential biases have been noted. There are significant differences in the character of the agreement between ATLAS 1 and ATLAS 2 which will require further study.

Scattering models for the solar infrared F-corona brightness

Model calculations are made of the infrared brightness in the solar F-corona motivated by recent infrared solar eclipse observations. Two different approaches are employed to describe the scattering properties of interplanetary dust : Mie scattering theory and diffraction theory, with and without an isotropic scattering term. In addition. two different particle size distributions are used in the calculations and the resultant line of sight brightness is compared with observational data of the solar F-corona between 3 and 8 solar radii ( R) in the ecliptic plane. It is found that the use of diffraction theory without an isotropic scattering contribution gives a very poor match with the observations, for both assumed particle size distributions. However, both the diffraction theory including isotropic scattering and the Mie scattering theory agree reasonably with the observed brightness, and especially its radial slope within the corona. for the model size distribution which is dominated by large particles. Only Mie theory may be employed in describing the second model size distribution because diffraction theory poorly describes the scattering due to the small particles which dominate this size distribution. It is concluded that the derivation of particle size distributions from the F-coronal brightness is still ambiguous and a further analysis needs either improved observations, or the application of further reasonable physical assumptions.

Accuracy of Solar Eclipse Observations Made by Jesuit Astronomers in China

Accuracy of Solar Eclipse Observations Made by Jesuit Astronomers in China

Paraconical pendulum as a detector of gravitational effects during solar eclipses (processing data and results)

A statistical analysis of data collected during observation of a total solar eclipse of July 11, 1991 at Mexico City is presented. The variation of the velocity of the azimuth of the major axis of the pendulum's oscillation ellipse during the eclipse is determined and the sudden deviation of the azimuth of the plane of swinging at the start of the eclipse is calculated.

Variation of the solar diameter from solar eclipse observations, 1715?1991

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.

Exploring the fine structure at the limb in coronal holes

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.

Tentative identification of formaldehyde in the Martian atmosphere

Solar occultation observations of the Martian atmosphere near the limb of the planet were performed during the Phobos mission by means of the Auguste infrared spectrometer in the ranges 2707–2740 and 5392–5272 cm −1 with a resolving power of ≈ 1300. The spectra exhibit features at 2710 and 2730 cm −1 which have not been identified previously. After applying a set of corrections to the data and examining the spectra of various molecules, we are led to conclude that the best candidate for the above-mentioned features is formaldehyde (CH 2O). It was observed in eight of the nine successful occultation sequences, mainly between 8 and 20 km with an average mixing ratio of 0.5 +0.8 −0.3 ppm (there are no good data below 8 km). The observations are performed in equatorial spring conditions. The altitude distribution of formaldehyde reveals correlation with the permanent haze opacity.

Correction to the field of view for the high altitude observatory mark III K-coronameter

The field of view widely in use for representation of the coronal data collected with the Mark III K-coronameter at Mauna Loa is incorrect. Analysis of the observations of a partial solar eclipse in August 1980 and of observations of high eruptive prominences seen both with the K-coronameter and the occulted Hα chromospheric telescope at Mauna Loa indicate that the field of view actually begins 0.09 R⊙ higher than thought; the pixel-to-pixel separation is as originally published. We describe the analysis which leads to the description of the image scale and discuss both the qualitative and quantitative effects of this new information on published results.

Vertical Structure of Martian Dust Measured by Solar Infrared Occultations from the Phobos Spacecraft

Solar occultation observations of the Martian atmosphere from the Phobos spacecraft resulted in nine vertical profiles of volume extinction coefficient at 3.7 and 1.9 μm in the altitude range of 12-35 km. Interpretation of the profiles in terms of the Mie scattering theory, with the adopted refraction index 1.5-0.01 i and particle size distribution of gamma-type, gives vertical profiles of the particle number density and the effective radius (weighted-mean extinction cross-section). The number density ( n) is found to be typically 0.2-1 cm -3 between 15 and 25 km; the effective radius ( r eff) varies from 0.8 μm near 25 km to 1.6 μm at 15 km. Average values of these parameters are n = 0.32 ± 0.15 cm -3 and r eff = 1.26 ± 0.2 μm. The dependence of these parameters on the refraction index and an effective variance of the size distribution is also studied. The data can be interpreted by a one-dimensional dynamic atmospheric model with a source of aerosol of 3 · 10 -12 g/cm 2/sec near 22 km. The derived mixing coefficient, K = (1.1 ± 0.5) · 10 6 cm 2/sec found to be independent of height between 15 km and 30 km ( d log K/dz ≤ 0.025 km -1). The width of the particle size distribution, v eff, is estimated with the modeling from the vertical profiles of particle number density assuming it is independent on height: v eff = 0.2 ± 0.1. Mean value of the total optical thickness obtained by extrapolation of the extinction profiles to the surface, assuming dust scale height equal to that of gas, is 0.24 ± 0.06 at 1.9 μm.

Combined radiation mechanism in the sun's active region No. 75 during the eclipse of 16 February, 1980

We assume that the physical conditions above an active solar region vary continuously from the centers of sunspots to the adjacent quiet region and try to take into account the influence of the magnetic field. Thus we calculate the three-dimensional distribution of the electron temperature and density based on the radio spectrum of active region No. 75 obtained from the solar eclipse observation of 16 February, 1980. If we assume a potential field, we calculated the magnetic field above the active region in terms of the solar photospheric magnetic field. Using the electron temperature, density, and the magnetic field as described above, and assuming the slowly varying radiation mechanism to consist of bremsstrahlung and gyro-resonance radiation, we obtained the flux density spectrum and the brightness temperature spectrum. The calculated results are essentially consistent with the observations.

Hydrocarbons and eddy mixing in Neptune's atmosphere

The most recent analysis of the Voyager ultraviolet solar occultation observations at Neptune indicates a methane mixing ratio 1–10 times above saturation in the lower stratosphere, unlike the value of 500–1000 times saturation which was suggested just before the encounter of Voyager with Neptune. The acetylene mixing ratio in the 0.1 mb region is found to be (6–8) × 10 −8, which is approximately a factor of 3 lower than the value reported in our Voyager/Science paper. The eddy diffusion coefficient at the homopause, (1–3) × 10 7 cm 2 s −1, is found to be more like that on Saturn than Uranus. The new results on CH 4, C 2H 2 and K have strong implications for the stratospheric temperatures, now warmer, and the source of heating. Furthermore, the pre-Voyager models of the hydrocarbon hazes need to be revised in view of the new model atmosphere.

Submillimeter solar limb profiles determined from observations of the total solar eclipse of 1988 March 18

Observations were made of the extreme solar limb in six far-infrared wavelength bands ranging from 30 to 670 micron using the Kuiper Airborne Observatory during the total eclipse of the sun on 1988 March 18. By observations of the occultation of the solar limb by the moon, it was possible to obtain a spatial resolution of 0.5 arcsec normal to the limb. The solar limb was found to be extended with respect to the visible limb at all of these wavelengths, with the extension increasing with wavelength. Limb brightening was observed to increase slightly with increasing wavelength, and no sign of a sharp emission spike at the extreme limb was found at any of these wavelengths. The observations can be well fitted by a chromospheric model incorporating cool dense spicules in the lower chromosphere.

Solar occultation observations of the Martian atmosphere in the ranges of 2–4 and 4–8 keV measured by phobos 2

Occulations of the Martian atmosphere measured during two solar flare events are studied to obtain density and temperature profiles in the altitude range from 80 to 130 km. The temperature profile observed at enhanced solar activity ( F 10.7cm = 201) demonstrates a temperature wave with an amplitude of 15 K and a length of 20 km similar to those observed by the Viking probes. The profile measured at very high solar activity ( F 10.7cm = 257) shows a steep increase of temperature in the range of 110–125 km which is caused by the downward heat flux and results in a solar EUV heating efficiency of ϵ = 0.1. The structure of this profile between 85 and 110 km may be explained by a temperature wave and/ or eddy cooling and turbulent heating of the atmosphere.

Solar eclipse observation: some simple devices

The terrestrial solar irradiance is evaluated in view of the energy absorbed by the retina and the blue light hazard. The evaluated irradiance is compared with the known safety standard, to determine the safety requirement of solar eclipse observation devices. Simple devices are then proposed. The first is a folded pinhole camera, giving a magnified sun image from a relatively small box. The second is a pinhole projector, used to display the image in a large room, while the third is a compact multimirror periscope enabling one to see the sun sharper than with a pinhole camera.