The Structure of the Heliospheric Current Sheet: 1978-1982,
STANFORD UNIV CA INST FOR PLASMA RESEARCH
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The structure of the heliospheric magnetic field changes substantially during the 11 year sunspot cycle. The authors have calculated its configuration for the period 1976 through 1982 using a potential field model, continuing their earlier study near solar minimum in 1976 - 1977. In this paper they concentrate on the structure during the rising phase, maximum, and early decline of sunspot cycle 21, from 1978 to 1982. Early in this interval there are four warps in the current sheet the boundary between interplanetary magnetic field IMF toward and away from the Sun giving rise to a four-sector structure in the IMF observed at Earth. The location of the current sheet changes slowly and extends to a heliographic latitude of approximately 50 deg. Near maximum the structure is much more complex with the current sheet extending nearly to the poles. Often there are multiple current sheets. As solar activity decreases the structure simplifies until, in most of 1982, there is a single, simply shaped current sheet corresponding to a two-sector IMF structure in the ecliptic plane. The Suns polar fields, not fully measured by magnetographs such as that at the Stanford Solar Observatory, substantially influence the calculated position of the current sheet near sunspot minimum. We have determined the strength of the polar field correction throughout this period and include it in our model calculations.