Interferometric investigation of the red and green coronal lines during the total solar eclipse of May 30, 1965

Abstract

Fabry-P6rot interferometric observations of the corona were carried out. The 6374 A line shows radial velocities between 10 and 70 km sec -1, both positive and negative. Most profiles of the 6374 A line are not Gaussian. The widths of the lines indicate unacceptably high temperatures, and thus suggest turbulent velocities, which appear to be of the same order as the line displacement velocities. Arguments are put forward that the corona consists mainly of individual non-turbulent knots with relative velocities similar to the measured ones. Purpose and ProgrammeObservations of the solar corona with a Fabry-P6rot interferometer were made during the total eclipse of May 30, 1965 in the 5303 A Fex~v and 6374 A Fex lines. About 20 attempts of interferometric observations of the corona are known, but successful results were obtained only in the excellent works of Jarret and yon Kltiber (1955Kltiber ( , 1961. Preliminary results of the present work were published by the authors in 1967.The purpose of the work is to obtain simultaneous information on the temperature and velocities of the coronal material in a considerable part of the inner corona (not only along the slit, as in spectroscopic observations) and with such data to attempt to find the reason for the existing discrepancy of the values of temperatures, obtained from the ionization theory and from the widths of the coronal lines. The red and the green coronal lines were chosen not only for their brightness, but also because they are currently used for obtaining the standard non-eclipse information on the temperature of the corona.According to our purpose we had to photograph the corona through narrow interference filters in the 6374 A and 5303 A lines and through the same filters and additionally Fabry-P6rot interferometers. For many points of the corona we had to obtain the line profiles, and, accordingly, the kinetic temperature and the ratio of intensities for these wavelengths. From these data it should be possible to derive the ionization temperature. Filter observations are taken to examine possible brightness irregularities in the corona. For instance to find out whether different parts of the profiles are due to the superposition of fine structures in the coronal radiation.In our observations the mean half-width of the coronal lines was 0.15 mm. A simple calculation shows that a homogeneous decrease of brightness in the corona of the order of 10 over one solar radius, which corresponds to the average coronal model, would not alter the half-width of the profile, but would somewhat shift the wings to Solar Physics 9 (1969) 116-130; 9 D. Reidel Publishing Company, Dordrecht-Holland

Coronal emission line profile observations at total solar eclipses

“…At q5=284 ~ in fringe 3 Vo= +7 kms -I. In the outei fringe a Doppler velocity Vo = -2 km s-~ is detected at ~b = 284 ~ These data indicate that the coronal material has only very small Doppler velocities in this region, in marked contrast to the results of Delone and Makarova (1969) who list velocities in this region up to 149 km s -1 and indicate a much greater irregularity in motions than are indicated from the present data.…”

Fabry-P�rot line profiles in the ?5303 � and ?6374 � coronal lines obtained during the 1983 Indonesian eclipse

“…The relative velocities in the corona we found at the 1980 and 1983 solar eclipses are not comparable with the similar velocities found by Delone and Makarova (1969) from their Fabry-P4rot studies through clouds of the 30 May, 1965, eclipse, for we measured relative velocities within individual profiles while they measured the deviation of the maximum intensities of their 6374 A profiles from the positions expected from their interferometer spacing as calculated from krypton lines photographed before and after totality. Such large velocities were not found in the multi-slit studies of Livingston and Harvey (1982).…”

Observing the solar corona with a tunable Fabry-Perot filter

“…There are many reports of motions in the corona [14,15] ranging from < 10 km s −1 up to ∼100 km s −1 . To have a closer look at the spectral line profiles in the various features, we sampled the mean intensity in the boxes shown and plotted the results as a function of filter-offset voltage.…”