The coronal hole at the 7 March 1970 solar eclipse

Coronal interferograms in the lines of Fe xiv 5303 Å, He i 5876 Å and Fe x 6374 Å were obtained during the total solar eclipse of 10 July, 1972 (see Figure 2). He i emission was found in the chromosphere only. The upper limit of the D₃ equivalent width in terms of the coronal continuous background is 0.013 Å in the inner corona (r=1.15 R⊙). The λ6374 negative was taken with low contrast. The half width of 16374 is 1.0–1.08 Å for a limited area of the corona (P=88?104°, r=1.30?1.44 R⊙). A detailed photometry of the 5303 Å line was carried out and the behaviour of the half widths and equivalent widths were studied in different regions of the corona. The half width of λ5303 increases with distance from the Sun's center in almost all the studied regions (1.2 R⊙ ? r ? 1.7 R⊙). This increase corresponds to an increase of the non-thermal velocities with a gradient of 1–2 km s^-1 per 0.1 R⊙. The equivalent widths, expressed in the coronal continuous background intensity remain constant on the average.     

The coronal and interplanetary magnetic fields at the time of the solar eclipse of 7 March, 1970

The magnetic field in the outer corona and in interplanetary space has been calculated from the photospheric magnetic fields measured around the time of the 7 March, 1970 eclipse. The field-line maps are compared with eclipse photographs showing coronal structures out to about 12 r . The projected field lines as well as the observed streamers appear straight. This is caused by the rapid expansion of the outer corona and is not an indication of corotation. The calculations show that the angular velocity of the coronal plasma decreases rapidly with distance.The relation between magnetic fields and density enhancements is discussed. The field strength in the photosphere seems to determine the amount of mechanical heating of the lower corona. The density structure higher up in the corona will, however, depend decisively on the topology of the field, particularly on whether we are on open or closed field lines, and not simply on field strength.The calculations show a sector structure of the interplanetary field, which agrees well with spacecraft observations. Also the magnitudes of the observed and calculated interplanetary field agree after the Mt. Wilson magnetograph data have been corrected to account for the temperature and saturation effects in the spectral line Fei 5250 Å.On leave from the Astronomical Observatory, Lund, Sweden.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Observations of the 7 March, 1970 total solar eclipse at wavelengths of 3.2 and 8.3 mm

The 7 March, 1970 total solar eclipse was observed at wavelengths of 3.2 and 8.3 mm; the object being to use the knife edge of the Moon as it passed across the Sun to improve angular resolution on the Sun. This in turn would provide a radial brightness distribution of the Sun with an angular resolution of a few seconds of arc.Excellent eclipse curves were obtained at 3 mm; however, some external interference marred the 8 mm record near totality.The 8 mm brightness distribution is subject to some uncertainty, but tends to show limb brightening. The 3 mm brightness distribution shows a well defined complex limb brightening within about 1 arc min of the optical limb. The maximum brightening is approximately 30% above the average disc temperature.     

Some newly discovered coronal emission lines from high altitude infrared observations of the 7 March, 1970, solar eclipse

A survey of the infrared coronal spectrum between 1 and 3 was made from a high altitude aircraft during the 7 March, 1970, solar eclipse. The observations were made with a Fourier transform spectrometer and were confined to the outer chromosphere and inner corona. In addition to well known chromospheric lines of Hi and Hei, nine additional lines were seen. Evidence is presented for the tentative assignment of these lines to forbidden transitions in highly ionized atoms of magnesium, aluminum, silicon, sulphur, and chromium.     

The chromosphere in continuum emission observed at the total solar eclipse on 7 March 1970

Direct images of the Sun were photographed in continuum emission centered at 6900 Å by the jumping film method near the second contact of the Mexico eclipse on 7 March 1970. The band width was 150 Å defined by a combination of a sharp cut filter and KODAK IV F film. The intensity distribution of the solar outer layers obtained shows a steep decrease by a factor of 0.9 in logarithmic units around 2500 km. This is interpreted as the boundary of the chromosphere and corona. Spicules observed at 3500 km are explained by log n _e = 11.25 and T _e 6000 K. Discussions are made in relation to the other observations and some chromosphere models.     

Photography of the eclipse of 7 March, 1970 from two locations

In an effort to detect motion of material in the corona, photographs were made with identical cameras from Nejapa, Mexico and from Kinston, North Carolina, U.S.A. The time separation of these two places from the point of view of the Moon's shadow arrival is almost exactly one hour. Two Questars, equipped with Nikon camera bodies were employed. The focal length is such (1440 mm) that the corona just nicely fills a standard 35 mm frame. Eastman XR film was used, in order to look at various radial portions of the corona, and a range of exposures from 0.1 to 4 s was programmed. The intent of the experiment was to seek some identifiable feature such as a condensation or intenser region and to determine whether it had moved appreciably in the time available. No motion was detected in any feature observable, from which a conclusion is drawn that the velocities were less than about 20 km/s. The data was sought in connection with our studies of the possible mechanisms of acceleration of particles in the Sun.Supported in part by NASA contracts NAS 1-5209 and NAS 1-10282.     

Mauna loa coronagraph observations around the 7 March 1970 eclipse

The locations of seven principal coronal features observed in projection at the 7 March 1970 eclipse are established from synoptic coronagraphic measurements.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

On emission lines of hydrogen,helium and ionized calcium seen on a coronal spectrogram of the March 7, 1970 eclipse

Emission lines of the Balmer series, D₃ and H and K are reported present on a coronal spectrogram obtained at the March 7, 1970 eclipse. Arguments are presented to show that these could not have originated from scattering in the Earth's atmosphere and hence possibly have a coronal origin.     

The radial brightness distribution of the Sun at 3.2 mm as determined from the June 30, 1973 total solar eclipse and a reanalysis of the March 7, 1970 total solar eclipse

The radial brightness distribution of the Sun at 3.2 mm is recalculated for the 7 March, 1970 total solar eclipse by an improved method. The results from the first contact of the 30 June, 1973 total eclipse are also analyzed. Limb brightening is apparent for the 1970 eclipse when all four contacts are averaged. The 1973 eclipse indicates strong limb brightening, although the detailed shape differs from the 1970 eclipse.     

On the coronal lines in the chromosphere at the 1970 eclipse

Spectrographic observations of the flash spectrum were made by the Kwasan Observatory at the total solar eclipse on 7 March, 1970. The integrated intensities of Fexiv 5303, Fex 6374, and the continuum were measured on the spectrograms as a function of height above the Sun's limb. It was found that a large amount of emission in the coronal lines originates in the interspicular regions of the chromosphere. Analysis of the data yielded that the interspicular regions consist of coronal material of T _e = 1.6 × 10⁶–1.2 × 10⁶ and log N _e = 8.5–9.5, and that a decrease in T _e and an increase in N _e occur with decreasing height.     

The physical conditions in inner corona derived from spectral data of the solar eclipse on 7 March, 1970

The spectrum of the solar corona obtained during the eclipse of 7 March, 1970 has been studied. From the analysis of the line halfwidths it is concluded that the emission of coronal lines of various groups arises in different volumes of the corona. The lines 5303 and 4231 are analyzed in detail and by the use of the equations of excitation and ionization balance. The distribution of electron temperature T _e and density n _e vs height in the solar corona has been found. The usually adopted n _e and T _e are noticeably less than those values obtained in present analysis. This discrepancy may be due to the fact that the considered area of the corona seems to be in an unusual condition.     

A search for the K-line of CaII during the eclipse of 7 March, 1970

Conclusions At the 7 March, 1970 total eclipse, there were no significant differences between intensity levels between K-line and H-line, nor were there any finely structured features in the upper atmosphere of the sun in H larger than 2.5. The two H features close to the limb, though unexpected, do not appear to be remarkable.Operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.     

The results of coronal investigation at the September 22, 1968 solar eclipse

The 1968 Abastumani Astrophysical Observatory Solar Eclipse Expedition obtained photographic records of the polarization and intensity of the solar corona on September 22 from a site of the South Urals (Western Siberia). A photometric study of the corona was carried out. Polarization has been computed both in a total corona and in some of its streamers. The coronal intensity I _k and I _F components are separated. Electron concentrations and temperatures are computed.     

Localization of the source of flare X-ray emission during the eclipse of 7 March, 1970

An occultation of X-ray emission from a solar flare occurred during the eclipse of 7 March, 1970 and was observed by an NRL instrument aboard the OSO-5 satellite. Ionization chamber photometers covering the wavelength ranges 0.5–3 Å, 1–8 Å, and 8–16 Å provided flux measurements once every 15 s providing a spatial resolution of 20 arc sec at the solar surface. Within this limitation the X-ray flare was observed to be confined within a region 136 000 km in one dimension.However, the measurements indicate the existence of a denser core 54 000 km wide in the direction of advance of the Moon's limb. Comparison of these results with X-ray photographs of flare regions are made and a model for the development of the soft X-ray flare is proposed.     

Spectrophotometry of the corona and a quiescent prominence based on observations of the total solar eclipse of 7 March, 1970 in Mexico

Slit spectrograms of a quiescent prominence and the inner corona (h2.5 arc min) in the range 3400–7000 Å (dispersion 6–10 Å/mm) were obtained. From an analysis of the Stark effect on the Balmer lines (up to number 36) the electron density in the prominence n _e = (7 ± 3) × 10¹⁰ cm^–3 was deduced. The kinetic temperature T _k and the non-thermal velocities _t, found from a simultaneous consideration of the Balmer and metal lines, are T _k 10 000 K and v _t6 km/s. Also the emission measure of the prominence along the line-of-sight was found: ME = 10³¹ cm^–5.In the coronal spectrum 24 coronal lines were found. Thirteen of these lines were identified and measured photometrically to get their absolute intensities, profiles and halfwidths. For nine lines the intensities as a function of the height were studied and on this basis the coronal lines were divided into a few groups. The line-of-sight and non-thermal velocities are _r 10 km/s and _t 25 km/s. The coronal lines originate in at least three types of regions with different temperatures. The emission measure as a function of the ionization temperature was determined. The abundances of four elements of the iron group (V, Cr, Mn, Co) were estimated. The abundances of the other elements of the same group (A, Ca, Fe, Ni), found from EUV-data, are in a good agreement with our observations. The degree of inhomogeneity in the corona was estimated: .     

Correlation of photospheric magnetic field strength with coronal brightness on 7 March, 1970

The common observation that where photospheric magnetic fields are strong, the overlying corona is bright is examined quantitatively. White light coronal brightness is employed because it is independent of coronal temperature and is directly related to coronal electron density. Brightness data for the inner corona on 7 March, 1970, taken from isodensitometer traces having a resolution of 10 arc sec, are utilized. The data were obtained from photographs which exhibit distinct chromospheric features 5 arc sec or smaller. These data are quantitatively compared, using cross correlation and scatter plot techniques, with the corresponding photospheric magnetic field data provided by Kitt Peak National Observatory. Cross correlation coefficients are computed between latitudes ±55° at specified heights. In general, a statistically significant positive correlation is found. The correlation decreases with height in the corona. However, a range of values in several parameters remains to be investigated so the physical significance of the presently observed correlation is not yet entirely clear. We expect that refinement of our input parameters will produce a more sensitive correlation and lead to an expression for the relationship of electron density to photospheric magnetic field strength.NAS/NRC Research Associate.     

Analysis of an elongated narrow coronal streamer observed at the 1973 solar eclipse

A detailed photometric analysis has been made of a narrow elongated coronal streamer observed at the 1973 total eclipse. After deriving real intensity distributions, the electron density has been deduced under the assumption that the distribution is axially symmetric and that the decrease in density from the central axis follows the gaussian law. The results show that the gradient of the electron density is much steeper at the lower part, nearest to the solar limb, than those reported previously for larger scale streamers.On leave from the Observatorio de Huancayo, Instituto Geoflsico del Peru as a trainee of the Japan International Cooperation Agency.     

Observations of the total lunar eclipse on March 24, 1978, at 3.4-mm wavelength

Observations of the total lunar eclipse were made at 3.4-mm wavelength (87.4 GHz) on March 24, 1978. Eclipsr cooling curves with the best S/N ratio among those published thus far were obtained for the three points (the mountain area near the crater of Hipparuchus, Sinus Medii, and Copernicus). Each of the curves can be decomposed into the three parts which apparently correspond to ingress, totality, and egress. The derived cooling rate and heating rate differ significantly at the three points.     

Lamb waves generated by the 1970 solar eclipse

The Lamb waves excited by an eclipse induced cooling of a cloud bearing tropospheric region are invoked to explain an experimental result obtained in the 7 March 1970 solar eclipse. Quantitative investigations are severely handicapped by the lack of data concerning the cooling rates throughout the region, but show that if this cooling rate is of the order of magnitude of the ‘lost’ insolation the Lamb waves will explain the observed ground level pressure fluctuations.     

Observations of a partial solar eclipse at 9 mm wavelength

Observations at 9 mm wavelength of the partial solar eclipse of February 25th 1971 were made to investigate possible limb brightening of the Sun. The results obtained show that less than 5% of the solar disc power can be contained in any such brightening.