The white light coronagraph data from Skylab is used to investigate the equatorial and polar K and F coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R.) during the period of observation (May 1973 to February 1974 lead to the conclusions that: (1) the equatorial corona is dominated by either streamers or coronal holes seen in projections on the limb approximately 50% and 30% of the time, respectively; (2) despite the domination by streamers and holes, two periods of time were found which were free from the influences of streamers or holes (neither streamers nor holes were within 30 ~ in longitude of the limb); (3) the derived equatorial background density model is less than 15% below the minimum equatorial models of Newkirk (1967) and Saito (1970); (4) a spherically symmetric density model for equatorial coronal holes yields densities one half those of the background density model; and (5) the inferred brightness of the F-corona is constant to within + 10% and +5% for the equatorial and polar values, respectively, over the observation period. While the F-corona is symmetric at 2Ro it begins to show increasing asymmetry beyond this radius such that at 5Ro the equatorial F-coronal brightness is 25% greater than the polar brightness.

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 systern and the prominence.On large-scale photographs obtained at the November 12, 1966 eclipse, detailed photometry has been carried out on a formation in the corona composed of a helmet streamer straddling two multiplearch systems each with a dark cavity and a quiescent prominence. The excess of electrons in the arches and the deficiency in the cavities are evaluated. We find that the formation of a prominence requires much more material than available in the cavity before depletion. Consequently the condensation theory of coronal matter into prominences seems to have difficulties explaining the necessary amount of matter in the cases where coronal arches -delineating magnetic field lines above the cavity -may exclude inflow of matcrial from the corona. We comment on the low velocity of solar wind in the helmet streamer.

A typical concentric ellipse multiple-arch system was observed in the solar corona during the February 4, 1962 eclipse in New Guinea. The following results have been obtained from analysis of a white-light photograph taken by N. Owaki (see OWAKI and SArro, 1967a).(1) The arches are composed of four equidistant components, elliptical in shape, and almost concentric with a prominence at the common center of the ellipses.(2) The prominence and arch system appears to be the lower region ofa hehnet-shaped streamer.(3) The widths of the arches are observed to increase with height.(4) Analysis was made in the light of three models for the coronal structures that could lead to the observed arches: (a) rod-like concentrations of electrons; (b) tunnel-shaped elliptical shells of electrons; and (c) dome-like ellipsoidal shells of electrons. Electron densities are derived for the models, and the dome-like model is excluded as a possibility for arch systems exhibiting a coronal cavity.(5) The scale height in the arch-streamer region is found to be almost the same as that of the K-corona, suggesting equal temperatures, density distributions, etc. in each region.(6) There is a dark space (a coronal cavity) between the innermost arch and the prominence. The brightness of this cavity is 1 that of the adjacent arch. It is 3 % brighter than the background corona of the arch-streamer system.(7) A comparison is made between the deficiency of electrons in the coronal cavity and the excess of electrons in the prominence. It is found that the ratio of the excess to the deficiency lies between 0.9 and 40.(8) A comparison between the electron efflux from the 'leaky magnetic bottle' possibly formed by rod-shaped coronal arches and the electron influx into those arches from the chromosphere leads us to the conclusion that the rod model is probably valid and that spicules appear to be an adequate supply for the electrons observed in the arches. The tunnel model may be valid, but in that case spicules are probably not the sources of the electrons observed in coronal arches.

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