Energy and mass content of high-speed solar-wind streams

Abstract

The mass and energy flux densities of the solar wind measured by the Vela 3, Vela 4, and Explorer 34 satellites between July 1965 and October 1969 have been examined. Three-hour averages were used to study the properties of large-scale high-speed streams, and 27-day averages were employed in an attempt to identify long-term trends during the rising part of the current 11-year solar cycle. If the cross-sectional area of a stream is estimated by assuming that its extent in heliocentric latitude is the same as its extent in longitude, the total energy (at 1 AU) and mass flux can be calculated by integrating the excess mass and energy flux density above the predisturbance level during corotation of the stream past the observing satellite. The average energy and mass fluxes for dominant high-speed streams are found to be 9 × 1025 erg/sec and 8 × 109 g/sec, respectively. The total mass and energy output of all streams emanating from the sun over a typical 27-day interval, assuming that all last for the entire 27 days, is estimated to be less than 10% (∼7%) of the total solar-wind output from the same range of heliocentric latitudes (generally ±15°). Both large-scale streams and interplanetary shocks are found to contribute relatively little to 27-day average values of either mass or energy flux density. Thus, even though the amount of mass or energy or both per disturbance appeared to increase with increasing solar activity, the solar-wind energy and mass flux density averaged over a solar rotation remained remarkably constant.