Showing papers on "Solar eclipse published in 1973"

The arch systems, cavities and prominences in the helmet streamer observed at the solar eclipse, November 12, 1966

Abstract: Arch systems lying above quiescent prominences in the solar corona have long drawn the attention of eclipse observers, and such formations have been investigated since the end of the last century. Almost every eclipse photograph shows one or more arches, and in most cases the arch system is accompanied by a quiescent prominence below it and a helmet streamer above it. Also, in some cases there is a dark cavity between the arch system and the prominence.

Supersonic Generation of Atmospheric Waves

Abstract: Chimonas and Hines1 have pointed out that the Moon's shadow on the Earth's atmosphere during a solar eclipse constitutes a cooling region travelling at supersonic speeds, and may generate atmospheric gravity waves with periods from a couple of minutes up to twelve hours. Atmospheric wave generation by solar eclipses has been observed2–4, though within the source region (the region of total or partial eclipse) the gravity waves have substantially shorter period than outside it. Here I draw an analogy between the supersonic motion of the Moon's shadow and the supersonic motion of the Earth's terminator. The terminator is supersonic between ± 45° latitudes at all altitudes below 100 km and may therefore generate gravity waves in this region.

Atmospheric Gravity Wave Observations after the Solar Eclipse of June 30, 1973

Abstract: IT has been suggested that, during a solar eclipse, gravity waves are generated by the Moon's shadow moving with supersonic speed through the Earth's atmosphere1,2. After the eclipse of March 7, 1970, several investigators3–6 detected atmospheric gravity waves in the form of travelling ionospheric disturbances (TIDs) using different observational techniques. But it was not possible to decide definitely whether the TIDs were due to the eclipse or to any other sources.

Incoherent scatter radar observations of the auroral zone ionosphere during the total solar eclipse of July 10, 1972

Abstract: Observations of the behavior of the auroral zone ionosphere were made with the incoherent scatter radar at Chatanika, Alaska, during the total solar eclipse of July 10, 1972. The radar beam intersected the approximate center of the eclipse shadow at a height of 400 km. The electron temperature decreased by more than 1200°K, and the ion temperature decreased by approximately 100°K near eclipse totality. Electron concentrations in the E and lower F regions decreased by 50%. Concentrations above the F layer peak decreased slightly, but there was no net change in ionization at the F layer maximum. Apparently, downward diffusion of upper F region ionization was just adequate to balance the loss processes at the layer maximum. An estimate of the heat input to the electron gas at 340 km showed that this quantity fell to about 25% of its background value during totality. Control radar data for the eclipse observations were obtained on July 9, 11, and 12, 1972, along with supporting vertical incidence ionosonde and magnetometer data acquired near College, Alaska.

Eclipse Flight of Concorde 001

Abstract: On June 30, 1973, Concorde 001 intercepted the path of a solar eclipse over North Africa, Flying at Mach 2.05 the aircraft provided seven observers from France, Britain and the United States with 74 min of totality bounded by extended second (7 min) and third (12 min) contacts. The former permitted searches for time variations of much longer period than previously possible and the latter provided an opportunity for chromospheric observations of improved height resolution. The altitude, which varied between 16,200 and 17,700 m, freed the observations from the usual weather problems and greatly reduced atmospheric absorption and sky noise in regions of the infrared.

The radio radius of the Sun at millimeter and centimeter wavelengths

Abstract: The radio radius of the Sun is determined from an analysis of the radio contact times of the 7 March, 1970 and 10 July, 1972 solar eclipses from λ = 3 mm to λ = 31 cm. Agreement with other eclipse measurements is good. A best fit curve through the several points gives the radio radius to within approximately ±0.01 of the photosheric radius below λ∼-5 cm.

Stratospheric cooling and perturbation of the meridional flow during the solar eclipse of 7 March 1970.

Abstract: Eight ARCAS meteorological rockets were fired from Wallops Island (38N, 75W) before, during and after the total solar eclipse of 7 March 1970. Detailed temperature and wind data were acquired to an altitude of about 65 km. Pressures and densities were derived by hydrostatic integration of the corrected temperature profiles. A time-height cross section of the temperature data (smoothed to suppress small-scale detail) shows significant cooling mainly in the layer 40–60 km. Maximum amplitude of the temperature perturbation is about 9K, near 50 km. Maximum pressure variation, amounting to a decrease of at least 7%, occurred about one scale height higher, near 58 km. The ARCAS wind observations are independent of the thermodynamic measurements; a time-height analysis of the winds shows a large amplification of the meridional flow, which is found to be consistent with the observed pressure changes. Derivatives in the perturbation equation of motion are evaluated with the aid of a space-time transformat...

The λ 747 coronal line at the 1966 eclipse

Abstract: Observations are presented of emission line resonance polarization in Fe xiii λ10747 at the total solar eclipse of 12 November 1966. Useful data, with angular resolution 15″, describe three quadrants of the corona from 1.08 R⊙ to a maximum of 1.6 R⊙. The direction of the electric vector of observed polarization is perpendicular to the solar limb, to the limits of accuracy of measurement, in at least 74% of all cases. Departures in the other points are consistent with the magnetic depolarization expected from the non-radial fields of streamers. Polarizations observed range from near zero at the limb to 80 % and higher at 1.6 R⊙. Averaged polarization is highest in non-streamer regions, where above 1.2 R⊙ it suggests pure radiative excitation of the λ10747 line. Below 1.2 R⊙, and in a dense streamer, the polarization is significantly depressed, indicating dominant collisional excitation of the line wherever the electron density exceeds 50 × 106 cm−3.

Extreme ultraviolet emission from chromospheric inhomogeneities An analysis of the extreme ultraviolet flash spectrum of the sun

Abstract: An Aerobee 170 rocket carried five slitless extreme ultraviolet (XUV) spectroheliographs into the March 7, 1970, solar eclipse. Salt water damage left latent images on 16 exposures of the XUV camera covering the wavelength range from 1390 A to 1945 A. The salt water damage made the absolute calibration of the spectroheliograms uncertain. Therefore, the analysis in this paper is based on a comparison of the extent of flash spectrum crescents from emission lines formed in the chromosphere-corona transition zone with two simple but fundamentally different models describing this region. The observations can be satisfactorily described by an inhomogeneous model where cool spicules are surrounded by a transition zone which has the same temperature and density structure as the chromospheric coronal transition zone customarily used in spherically symmetric models of the quiet Sun.

Predicted acoustic gravity wave enhancement during the solar eclipse of June 30, 1973

Abstract: It is concluded that Faraday rotation observations using a synchronous satellite at 10 to 15 deg W may exceed those obtained on the Starford-ATS1 link by a factor of 10 or more and that this unique enhancement may serve to identify those ionospheric irregularities due to the eclipse from a background of random and unrelated events. (WDM)

Search for Atmospheric Gravity Waves induced by the Eclipse of June 30, 1973

Abstract: It was suggested that atmospheric gravity waves could be generated by the supersonic passage of the moon's shadow through the earth's atmosphere during a solar eclipse, and it was thought that the eclipse of June 30, 1973 might provide an opportunity of investigating this idea. Gravity waves were predicted to have a period of 4 hr and amplitude 10 mu bar at a position 10,000 km from the eclipse path. For the experimental observations a microbarograph was employed, having a variable pass band; this instrument is described in detail. The trace for the period during which the gravity waves might have been expected was very noisy'' due to weather conditions. There were two principal features on the trace; first, a sine wave with period 15 min and amplitude 60 mu bar starting at 1257 UT; secondly, a sharp decrease in pressure at 1314 UT which sert the instrument off scale for about 2 min, after which the trace returned to its original noisy pattern. These two features could possibly have been noise'', but no other such isolated feature was recorded during 50 days of almost continuous operation. There were no meteorological fronts in the vicinity at the time of observation,more » and the duration was far too long to be the product of a sonic boom. Assuming great circle tracks and a speed of propagation of 320 m/sec the gravity wave should have reached the instrument after 1353 UT. It therefore seems that the features recorded could not have been due to the eclipse. (UK)« less

Observing total solar eclipses from near the edge of the predicted path

Abstract: Suitable observations from various locations in the predicted path of a total solar eclipse can provide information about the relative positions and shapes of the Sun and Moon to about ±0″.02. The total solar eclipse of 1972, July 10 was observed from locations near the edges of its predicted path. The durations of the limb phenomena were greatly enhanced. Preliminary analysis of the observations shows that the eclipse shadow passed 3 km northeast of its predicted path.

An investigation of solar eclipse effect on the subpolar stratosphere

Abstract: : An experiment to study the effect of partial solar eclipse on the stratosphere was performed at Poker Flat, Alaska (65 degrees 07 minutes N, 147 degrees 28 minutes W), where a partial solar eclipse occurred on July 1972. Chemiluminescent ozonesondes were deployed by Arcas Meteorological rockets to an altitude of 50-55 km. After ejection the sensors descended via radar reflective parachutes and transmitted alternately ozone content and ambient temperature. Soundings were made during the week of the eclipse as well as during and immediately before and after it. Results obtained indicate that there was no significant effect due to eclipse on ozone concentration, temperature, and winds in the upper stratosphere of the subpolar region.

Ionospheric Response to Solar Eclipse.

Abstract: : Faraday rotation stations were installed at Nairobi, Dar es Salaam, Blantyre and Grahamstown and were operated for about ten days including the period of the eclipse on 30th Jun 1973. The records show that total electron content perturbations due to the eclipse were much smaller than other authors had forecast. Refinement of the raw data by filtering is in progress but the results are expected still to be difficult to interpret in terms of gravity waves. These observations agree with those of others so far published. (Author)

Ground Squirrel Behaviour During a Partial Solar Eclipse

Abstract: A partial solar eclipse on September 11, 1969 markedly affected the locomotor activity of a captive antelope ground squirrel, Ammospermophilus leucurus. Both the amount of activity and the length of non-stop running sessions were much greater than normal during and for two hours after the eclipse. The results suggest that behaviour induced by an eclipse can be more complex than mere retiring and emerging responses.

FURTHER EVIDENCE FOR A COMPLEX LIMB STRUCTURE IN THE SOLAR RADIAL BRIGHTNESS DISTRIBUTION AT mm WAVELENGTHS

Abstract: A computer program to convolve numerically any azimuthally symmetric, solar radial brightness distribution with standard antenna patterns of small half power beamwidths has been used to find a solar brightness distribution which is a good fit to the eclipse curve obtained during the 7 March 1970 partial solar eclipse with the NRAO 36-ft antenna at 3.5 mm. This brightness distribution is compared with the brightness distribution at 3.2 mm determined by the Pennsylvania State University Radio Astronomy Observatory group during the same eclipse but observed from Mexico where totality occurred. The two brightness distributions are very similar in shape, showing a double peak near the limb, but differing slightly in the positions of the peaks.

Microwave observations of the 4 January, 1973 solar eclipse

Abstract: The eclipse was observed at two microwave frequencies, 7 GHz and 22.2 GHz, and has shown the presence of polarized regions, suggesting also excess of left-handed polarized radiation from the solar northern hemisphere. Difference in eclipsing times at the two frequencies for an active center near the limb is discussed.

On the Polarization of the Solar Coronal Emission Lines

Abstract: The results of the spectrophotometrical measurements of the polarization in the coronal lines Fe xIv 5303 fit and Fe x 6374 fit are given. Polarization spectrograms were obtained by two spectrographs (prism and echelle types) during the solar eclipse in Mexico on 7 March, 1970 near the region of the second contact at the heights 0.06 to 0.12 R| above the limb. The polarization in the green line is about 30 % (for averaged height 1.08 Ro). The polarization in the red line is close to the errors of the measurement and does not exceed 6 % A brief discussion of the results is also given.

Analysis of partial-reflection data from the solar eclipse of 10 Jul. 1972

Abstract: Partial-reflection data collected for the eclipse of July 10, 1972 as well as for July 9 and 11, 1972, are analyzed to determine eclipse effects on D-region electron densities. The partial-reflection experiment was set up to collect data using an on-line PDP-15 computer and DECtape storage. The electron-density profiles show good agreement with results from other eclipses. The partial-reflection programs were changed after the eclipse data collection to improve the operation of the partial-reflection system. These changes were mainly due to expanded computer hardware and have simplified the operations of the system considerably.