Solar cycle variation of the interplanetary magnetic field spiral

Abstract

view Abstract Citations (112) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar Cycle Variation of the Interplanetary Magnetic Field Spiral Smith, Charles W. ; Bieber, John W. Abstract Interplanetary measurements spanning the time interval from 1965 through 1987 and a distance range from 0.7 to 15.9 AU are employed to test the Parker (1958) theory for the large-scale structure of the interplanetary magnetic field. Examination of data recorded by earth-orbiting spacecraft reveals that the interplanetary magnetic field spiral depends upon the phase of the solar cycle, such that the annual mean winding angle in the years surrounding solar maximum is about 10 deg larger than in the years surrounding solar minimum. The observed variation of the solar wind speed with the solar cycle is shown to account for much of the recorded variation in the winding angle. It is suggested that nonzero azimuthal field components arising from differential solar rotation may be convected into the corona to provide a steady source of azimuthal magnetic fields at the source point of the solar wind. A straightforward extension of the Parker theory shows how such seed fields would account for the observed discrepancy in the interplanetary spiral winding. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169830 Bibcode: 1991ApJ...370..435S Keywords: Interplanetary Magnetic Fields; Solar Activity; Solar Cycles; Solar Rotation; Solar Wind Velocity; Coronas; Plasmas (Physics); Solar Physics; INTERPLANETARY MEDIUM; MAGNETIC FIELDS; SUN: ACTIVITY full text sources ADS |