Showing papers on "Solar eclipse published in 1984"

The study of the effect of solar eclipses on the ionosphere based on satellite beacon observations

Abstract: Satellite beacon observations during eclipses have provided much information on the behavior of the ionosphere. A combination of Faraday rotation and differential phase measurements as well as ionosonde data can provide information on the topside and bottomside ionospheric behavior during an eclipse as well as on the production rate. Recent attention has been directed toward a study of the dynamics of the F region during an eclipse and the relation between the amount of depletion in the total electron content and the percent obscuration of the sun. Of particular interest is the time delay from the maximum obscuration to the maximum depletion of the total electron content. Further modeling studies are required in order to reproduce the experimental results. Further observations are also required in order to establish whether TID's are generated following a total solar eclipse as predicted theoretically. In particular, it appears that a more sensitive technique such as differential Doppler rather than Faraday rotation is required. The total solar eclipse of June 11, 1983, with its long totality time of 4–5 min over Indonesia and Papua New Guinea will provide an ideal opportunity for further studies of these unanswered questions.

High-frequency coronal oscillations and coronal heating

Abstract: At the 1980 total solar eclipse, we searched for high-frequency (0.1–2 Hz) oscillations in the intensity of the 5303-A coronal green line, as a test of predictions of theories of coronal heating via magnetohydrodynamic waves. Portions of the image 2.5- or 5-arc sec across were fed to cooled photomultipliers using fiber-optic probes. We detected excess power in Fourier transforms of the data for the region between 0.5 and 2 Hz at the level of 1% or 2% of the incident power. Such oscillations could be associated with Alfven waves that are trapped on loops a few thousand kilometers long or with fast waves that are trapped on loops a few thousand kilometers in diameter. Additional observations at the 1983 eclipse are planned to resolve atmospheric and instrumental contributions.

Near-infrared observation of the circumsolar dust emission during the 1983 solar eclipse

Abstract: A near-infrared excess emission superposed on the coronal continuum at ∼4R⊙ from the Sun was first observed at 2.2 µm by Peterson1 and MacQueen2 during the total solar eclipse in 1966, and was later confirmed by MacQueen2 using a balloon-borne coronagraph. Two subsequent observations were made; one3 obtained a similar result, while the other4 detected no excess emission. The excess emission was thought to be due to thermal radiation by a dust cloud around the Sun, and interpreted to be interplanetary dust2. Brecher et al.5, on the other hand, have proposed that the ring is composed of much larger objects (of about 10 km diameter). To obtain more definite information, we have therefore carried out observations of near-infrared brightness distributions of the solar corona, using a balloon-borne photometer at a balloon altitude, during the total eclipse on 11 June 1983 in Indonesia. As we report here, emissions in excess of the strong coronal background emission were recorded in some of the scans at ∼4R⊙ from the Sun. The spatial distribution of the excess emission implies the existence of a circumsolar ring of dust lying approximately in the ecliptic plane.

Thermospheric response to the June 11, 1983, solar eclipse

Abstract: The NCAR thermospheric general circulation model (TGCM) that includes coupling of dynamics and composition is used to calculate the time-dependent thermospheric response to the June 11, 1983 total solar eclipse. The path of totality originated at sunrise in the Indian Ocean near 35°S and 60°E. The path moved equatorward passing through Indonesia near 5°S latitude 125°E longitude and ending near 20°S latitude and 165°E longitude in the vicinity of the Solomon Islands. Although the path of totality is relatively small, the area of partial shadow is relatively large, and the total flux incident on the dayside earth decreases by about 7% during the total eclipse. The TGCM calculates the time-dependent response of the winds, temperature, and mass mixing ratios of the major constituents throughout the thermosphere. Perturbations follow the path of totality, with maximum deviations occurring near 0530 UT at about 350 km. The winds converge from all directions toward the shadow at speeds reaching 60 m s−1 in the upper thermosphere. The maximum temperature anomaly (−70°K) and vertical wind anomaly (−8 m s−1) occur near the center of the shadow. The mass mixing ratio at N2 along a constant pressure surface decreases by up to 2%, and that of O increases by up to 2% in response to the sudden thermospheric cooling caused by the shadow passing over the dayside of the earth. At a constant altitude of 300 km the N2 and O number densities both decrease by about 6%. The time-dependent calculation shows that disturbances are generated during the onset of the eclipse, with the largest perturbations following the path of totality.

Traveling atmospheric pressure waves measured during a solar eclipse

Abstract: An array of microbarographs near Saskatoon, Saskatchewan, detected traveling pressure waves at a time and with a direction of motion that indicates an association with the solar eclipse of February 26, 1979. The velocity was 10 m/s moving toward azimuth 65°; the wave period and amplitude were approximately 120 s and 12.0 Pa, respectively; the duration of the wave train was approximately 3 hours. The probability that it was a free gravity wave is examined and rejected. A plausible source mechanism similar to the low level nocturnal jet is suggested.

Fabry-Perot interferometric observations of the coronal red and green lines during the 1983 Indonesian eclipse.

Abstract: During the total solar eclipse of 11 June 1983 over Java, Indonesia, a dual-channel Fabry-Perot interferometric system was used to study simultaneously the coronal emission lines at 5303 A (Fe xiv) and at 6374 A (Fe x) The two coronal lines were spatially separated by a multilayer interference beam splitter; the beams then entered two separate optically contacted Fabry-Perot systems operating off-axis The resulting interference fringes were imaged on fine-grain film Initial results indicate an emission corona confined largely within 12 R⊙ Doppler temperatures derived from the width of the 5303-A line appear to be appreciably lower than similar temperatures determined during the solar-maximum eclipse of 1980

Observations of shadow bands at the total solar eclipse of 16 february 1980

Abstract: Photoelectric observations of short term light variations (shadow bands) at the 16 Feb. 1980 total solar eclipse have been made using a set of spatially separated PIN diodes. Light variations in a bandpass of 1-500 Hz were detected during the half-minutes preceding and following the total phase. Fourier analysis of the noise spectrum of the variations reveals a sharp drop-off for frequencies above 50 Hz and an overall spectrum quite similar to previously reported power spectra of stellar scintillation. This is consistent with an atmospheric origin for the shadow bands. Cross-correlations between the detector outputs are low, suggesting a short persistence time for the turbulent elements causing the patterns.

Coronal Temperature Measurements Near a Helmet Structure Base at the 1973 Solar Eclipse

Abstract: Observations of coronal Fe XIV emission lines from the NE quadrant during the 1973 solar eclipse are reported. Temperatures are deduced from a pure thermal broadening model, and, in the region near an observed white-light enhancement, an alternative interpretation of halfwidth as being in part due to turbulent velocities is suggested.

Photometric analysis of the June 11, 1983 solar corona

Abstract: Observations de la couronne solaire le 11 juin 1983 durant une eclipse totale, a l'aide de differentes photocameras. Analyse morphologique des structures de la couronne K et analyse isophotometrique

The corona near the time of the 1983 June 11 total solar eclipse

Abstract: Observations are presented of the corona during the June 11, 1983 total solar eclipse, together with preliminary results of a coordinated observing program conducted to investigate the relationship between the corona and the lower parts of the solar atmosphere. Synoptic observations of the white light corona and disk in H-alpha are compared with the eclipse image, together with the inferred longitudinal component of the photospheric magnetic field measured using the magnetically sensitive Fe line at 6303 A. Using these data, an interpretation of the global three-dimensional coronal structure is attempted; showing that the eclipse image contains bright features which are far from the plane of the sky, and that it is dominated by streamers over polar filament neutral lines.

Brightness, polarization and electron density of the solar corona of 1980 february 16

Abstract: During the eclipse of 1980 February 16 we photographed the solar corona at an effective wavelength of 6300 a Using a quadruple camera we also obtained the coronal pictures in polarized light for four Polaroid orientations We have used these observations to derive the coronal brightness and polarization and from these the electron densities in the corona out to a distance of about 25 R⊙ from the centre of the disc The coronal brightness matches well with that of the corona of 1958 October 12

Structure of the inner corona derived from observations of the eclipse of 16 February 1980

Abstract: The volume emission measure EM(V) of the arch systems of the inner corona, not immediately associated with developed active regions, has been determined by analyzing the pictures of the green corona. It was found that the EM(V)-values of these systems are substantially lower than those obtained from X-ray data for the active regions, and this fact should be taken into account in interpreting extra-atmospheric observations. The combined investigation of data on the radiation of the corona in the green line and in the continuum enables one to determine the total extension of the radiating matter, (0.5–1) × 1010 cm, as well as the density in the separate arches, ≈ 1.5 × 109 cm-3. It is assumed that matter exists between the arches with a density of ≤ 108 cm-3.