Autocorrelation analyses of K-coronameter observations made at Haleakala and Mauna Loa, Hawaii, during 1964-1967 have established average yearly rotation rates of coronal features as a function of latitude and height above the limb. At low latitudes the corona was found to rotate at the same rate as sunspots but at higher latitudes was consistently faster than the underlying photosphere. There were differences as large as 3-4 % in the rate at specific latitudes fi'om year to year and between the two hemispheres. In 1967 a nearly constant rotation was found for heights ranging from 1.125 to 2.0 R0. For 1966 there was a more complicated pattern of height dependence, with the rate generally decreasing with height at low latitudes and increasing at high latitudes.

During the time period 1970-early 1973, 13 instances of major abrupt depletions of localized regions of the inner solar corona (1.1-2 Rq) were detected at Mauna Loa, Hawaii. Because of their almost invariable association with the ascending Ha prominence material (most generally flare sprays and, in one instance the disparition brusque of a large filament near the solar limb) and close correlation in time and position with outward moving Type IV radio sources, we surmise that the coronal material was expelled from the sun. In several of these cases plasma clouds were tracked to 10 Rq by Naval Research Laboratory with a coronagraph aboard OSO-7. Limited evidence suggests that some aspects of a coronal disturbance, including trajectory of flare spray and depletion of the inner corona, are homologous within 24 hours, so the overall coronal magnetic field configuration is not necessarily permanently altered.

We examined the sources of magnetic fields in recurrent streams observed by the Imp 8 and Heos spacecraft at 1 AU and by Mariner 10 en route to Mercury between October 31, 1973, and February 9, 1974, during Carrington rotations 1607–1610. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. However, some of the magnetic fields and plasmas at 1 AU were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines may be more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes, estimated by projecting the measured interplanetary magnetic fields back to the sun by using the principle of flux conservation, ranged from 2 to 18 G with an average of 9 G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 RS had a similar range and average, but in two cases the intensities were approximately 3 times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 RS, determined by a potential field extrapolation of the measured photospheric fields, meandered between −45° and +45° latitude, and their inclination with respect to the solar equator ranged from near 0° at some longitudes to near 90° at others. It is possible that sector boundaries are related to convergence surfaces of the flow near the sun. The high densities observed near sector boundaries between streams might be due in part to the convergence of flows from adjacent coronal holes.

The white‐light corona was observed regularly at the Mauna Loa Observatory during the years 1965–1967 and 1969–1978. Display of the measured polarization brightness in the form of synoptic maps permits the identification of large coronal holes and the study of their slow evolution during the sunspot cycle. The polar coronal holes were clearly seen to shrink in size during the ascending phase of cycle 20 (1965–1967), to be absent during a two‐year period (1969–1970) just after sunspot maximum, to reappear near the end of 1970, and to remain as prominent features of the corona for the years 1971–1978. During the sunspot maximum epoch the corona was dominated by ‘mid‐latitude’ holes, elongated in the direction parallel to the solar equator. Large equatorial holes or equatorward extensions of the polar holes were observed during the ascending, maximum, and descending phases of cycle 20 and appear to be sources of solar wind streams with maximum speeds over 600 km s−1 at all of these epochs. The lifetimes of these holes and streams were greatest during the descending phase of the cycle, or in 1974–1975.

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Using K-coronameter observations made by the High Altitude Observatory at Haleakala and Mauna Loa, Hawaii during 1964-1976, we determine the apparent recurrence period of white-light solar coronal features as a function of latitude, height, and time. A technique based on maximum entropy spectral analysis is used to produce rotational period estimates from daily K-coronal brightness observations at 1.125R s and 1.5R s from disk center and at angular intervals of 5 ~ around the Sun's limb. Our analysis reaffirms the existence of differential rotation in the corona and describes both its average behavior and its large year-to-year variations. On the average, there is less differential rotation at the greater height. After 1966-1967 we observe a general increase in coronal rotation rate which may relate to similar behavior reported for the equatorial photospheric Doppler rate. However, the coronal rate increase is significantly greater than the photospheric. If K-coronal features reflect the rotation at depth in the Sun, the long-term rate increase and the variable differential rotation may be evidence for dynamically important exchanges of energy and momentum in the upper convection zone.

Observations of the white light corona were made on over 900 days during the years 1964-67 at heights between 1.125 and 2.0R~ with the K-coronameter at Mount Haleakala and Mauna Loa, Hawaii. The brightness distribution of the minimurn corona was elliptical with average equatorial intensitics three times the polar. Coronal features of the new cycle at 1.125 R o occurred predominantly in the sunspot zones at 25..-30 ' latitude and in a high latitude zone which migrated toward the North pole before solar maximum. The brightness of the inner corona doubled over this period and a close association is found between the average corona and 10.7-cm solar radio flux. Electron densities in the equatorial regions were nearly twice those of Van de Hulst's model corona, in agreement with the results of recent eclipse observations.

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