Showing papers on "Solar eclipse published in 1981"

Dynamics of the atmospheric boundary layer during the 1980 total solar eclipse

Abstract: An atmospheric boundary layer experiment was conducted at Raichur, India to study the variations in the surface shear stress, heat flux and the meteorological processes that take place during a total solar eclipse. Interesting results were observed regarding the evolution of the planetary boundary layer. Changes in atmospheric stability from unstable to stable to unstable were observed during different phases of the eclipse. Downward propagation of negative heat flux associated with decreasing scales of convective eddies was also observed during the eclipse.

IR observations of the solar corona—a ring around the Sun?

Abstract: The possibility of a permanent ring structure around the Sun was first pointed out by Brecher et al.1 from evolutionary, physical and chemical considerations as well as constraints arising from observational astronomy related to Sun and its immediate neighbourhood. In particular, Brecher et al.1 concluded that such a ring, located at ∼4 R⊙, must consist of refractory particles (graphite, for example) of size >10 km at ∼1,000–2,000 K which, therefore, would emit thermal radiation peaking around 1.5–3.0 µm. We report here our attempt to detect the existence of this ring structure utilizing the IR observations taken during optimal viewing conditions of the total solar eclipse of 16 February 1980.

Modeling the ion chemistry of the D region: A case study based upon the 1966 total solar eclipse

Abstract: The November 12, 1966, solar eclipse has been modeled by a large multispecies chemistry code and the results compared with the numerous experimental measurements that were made at that time. Measured preeclipse values of electron density and code-predicted values agree closely if ionization by precipitating electrons from the radiation belts is included. Current gas-phase ion chemistry does not predict the rapid decrease and subsequent reconstitution of electron density about totality in the 65- to 85-km region, nor does it produce the large number of negative ions above 70 km that can be inferred from the experimental data. While basic constraints can be placed on the electron attachment processes because of the experimental data, an entirely new class of physical processes may need to be included to explain this phase of D region behavior.

Temperatures and differential line-of-sight velocities observed in the solar corona during a total solar eclipse.

Abstract: During the total solar eclipse on 16 Feb. 1980 over India we obtained a coronal interferogram in the Fe XIV green line at 5303 A. The objective of the experiment was to obtain a temperature map of the solar corona from the observed line widths. The experiment was carried out from Gadag, India (15° 25' N, 75° 37 ́ E). The interferogram was obtained using a 50-mm aperture optically contacted Fabry-Perot etalon (IC optical systems) with air spacing of 300 μm and finesse ~20. We confirmed the finesse at the end of the experiment by

Ionospheric Effects of the Total Solar Eclipse of 16 Feb. 1980 Observed over Ahmedabad

Abstract: Ionosonde observations and Faraday rotation measurements were made at Ahmedabad to study the ionospheric effects of the total solar eclipse of 16 Feb. '1980. Data on the eclipse day and control day (mean for 17-19 Feb. 1980)are presented in a comparative way. Decrease in the critical frequencies of E-. F1and F2-layers, viz.foE,foFI and foF2 and in the minimum frequency f;";o detected by the ionosonde, associated with the eclipse are noted. True height analysis of the quarter hourly ionograms shows decreases in the electron densities at various heights, the effects being gradually delayed at higher altitudes. Increase in the height of maximum F2-1ayer ionization (hmF2) and in the semi-thickness of the F2-layer (Yml are noted. A decrease in the total electron content (TEC) derived from the recordings of Faraday rotation at Ahmedabad is found during solar eclipse. No evidence of gravity waves, generated due to the eclipse and propagating in the ionosphere, could be detected from the continuous recording of foF2 or TEe.

Winter nighttime ion temperatures and energetic electrons from OGO 6 plasma measurements

Abstract: In the reported investigation, ion temperature and suprathermal electron flux data were acquired with the retarding potential analyzer on board the OGO 6 satellite when it was in solar eclipse. Attention is given to measurements in the 400- to 800-km height interval between midnight and predawn in the northern winter nonpolar ionosphere. Statistical analysis of data recorded during a 1 month time span permits a decoupling of horizontal and altitude effects. A distinct longitudinal variation is observed for ion temperature above 500 km, with a significant relative enhancement over the western North Atlantic. Altitude distributions of ion temperature are compatible with Millstone Hill profiles within the common region of this enhancement. Large fluxes of energetic electrons are observed and extend to much lower geomagnetic latitudes in the same longitude sector.

Solar limb brightening at 350 microns

Abstract: The NASA Infrared Telescope Facility at Mauna Kea was used to observe the intensity profile of the quiet solar limb in the 300-400 micron continuum. A significant resolved brightening of several percent over the outer 60 arcsec of the solar limb in this band is found. However, the magnitude of the brightening is considerably less than that indicated by earlier observations of a total solar eclipse in integrated sun-moon radiation by Beckman, Lesurf, and Ross (1975) in the 1.2 mm continuum. More recent ground-based observations indicate that the magnitude of solar limb brightening at 800 microns and at 1.3 mm is stronger than that at 350 microns. This may be regarded as an indication that the hot material which produces the brightening at the extreme limb, thought to consist in part of chromospheric spicules, is optically thin in the 350 micron continuum.

Solar quiescent prominences at 10.7 GHz

Abstract: Filaments on the Sun, which are dark linear features in the light of the Fraunhofer Hα line, are a mysterious feature of the solar surface. They are blade-like extensions of the chromosphere projecting to a height of 40,000 km into the corona, and may extend for up to 200,000 km along the surface. The fact that they may persist for a year or so, disappear abruptly and then reappear in the same positions shows that they are superficial indicators of deeper phenomena. There have been several reports1–4 of reduced brightness in the radio spectrum associated with the Hα filaments, leading to the widely accepted view that filaments are associated with broad dark radio features. This picture is, however, contradicated by our observations at 10.7 GHz of one solar filament during the solar eclipse of 12 October 1977.

A search of short-period coronal waves

Abstract: In 1973, during the total solar eclipse, we flew an experiment aboard the Concorde supersonic airliner in order to investigate the possible presence of white-light coronal waves. Our experiment failed to detect any significant effects, so it became clear that such waves should be searched for by use of finer, i.e., spectroscopic methods.

Zenith sky brightness and airglow emissions during the equatorial solar eclipse of 30 June 1973.

Abstract: Experimental and calibration procedures used for photometric zenith measurements at Loiyengalani (2.75°N, 36.6°E) during the total solar eclipse of 30 June 1973 are described briefly. Comparison was made between sky brightness at wavelengths in the 3914–6300-A range during totality and morning twilight at Dar es Salaam. The twilight 3914- and 6300-A sky background ratio is sometimes close to the expected value for a pure Rayleigh molecular scattering process, but the corresponding ratio at eclipse mid-totality is about one-third this, indicating a shift toward the red consistent with an atmosphere containing aerosols. The zenith sky brightness at 5600 A was <1 kR/A, somewhat lower than has been observed at low latitudes during the past 50 years. Comparison of the 6300-A line emission rate of 1.4 ± 0.6 kR with the Jan. 1974 Atmosphere Explorer satellite dayglow analysis suggests the main source of O(1D) atoms during totality is by excitation of O(3P) atoms in the lower thermosphere. About 1 kR of 5577 A was also observed, but the 5200-A emission was too low for reliable detection. An unexpectedly high 3914-A emission rate of at least 1 kR was apparent, the high rate being supported by observation at 4278 A.

High resolution interferometric observations of the solar limb at 4.9 and 10.7 GHz during the solar eclipse of October, 1977

Abstract: The radial intensity profile of the quiet solar limb has been measured at high spatial resolution using the VLA at 4.9 GHz and the Owens Valley solar interferometer at 10.7 GHz during the partial solar eclipse of October 12, 1977. The spatial resolution (13.8 arcsec at 4.9 GHz and 7.4 arcsec at 10.7 GHz) was provided primarily by the lunar limb. Substantial limb brightening at 4.9 GHz was found with a peak brightness temperature corresponding to an 80% increase over the disk value, and a possible small limb enhancement at 10.7 GHz. The results are consistent with a simple model consisting of a uniform disk (provided by a thoroughly roughened transition zone) overlaid by a corona in hydrostatic equilibrium with a density of 5 x 10 to the 8th at its base. The lack of the secant-like variation in the microwave intensity from center to limb is explained by a corona contained in loop structures rather than in spherically symmetric layers.

Analysis of the geomagnetic effect during the February 16, 1980 solar eclipse in Yunnan Province.

Abstract: Three-component (H. D. Z.) normal and quick run (H. D.) records of the earth's magnetic field were made at Ruili, Yunnan Province during Feb. 16, 1980, total solar eclipse. Daily variation, small disturbance and magnetic pulsation were analysed. There was a change of - 0.8' ± 0.2" in D and - 2.9 ± 1.6γ in H. The amplitude ratio of small disturbances was decreased. These changes are consistent with the change in electron density in the E layer during the eclipse.

Effects of total solar eclipse on mental patients-a clinicobiochemical correlation.

Abstract: Thirteen treated psychotic cases comprising of eight schizophrenic, four M.D.P. (manic type) and one M. D. P. (depressive type), who were clinically symptom free, were studied in respect of their hormones and behavioural abnormalities under effect of total solar eclipse. Of the hormones studied viz., T(2), T(4), TSH, Cortisol and prolactin, it is prolactin which showed an increase in titre associated with behavioural abnormalities in concerned patients during and immediately after the total solar eclipse. Deflection in both prolactin and behaviour gradually seemed to normalise over the post eclipse period.