Long-term variations of selected solar wind properties - IMP 6, 7, and 8 results

Studies of the variability of the solar wind are extended to include the minimum of solar cycle 20; attention is given to the He abundance, the relative He-H velocity difference, the He-H temperature ratio, the solar coronal proton density, speed, rms velocity variation, temperature and number flux, and the kinetic and total energy fluxes. The solar wind data are from observations conducted by the IMP-6, -7 and -8 satellites. A well-developed corotating stream structure appearing in January 1973 and disappearing in mid-1976 receives particular consideration. An increase in proton number and total energy fluxes after September 1972 may be due to areal expansion of both polar coronal holes, and may be associated with compression of the low-speed equatorial disk-shaped region postulated to surround the sun in interplanetary space.