IMF sector structure effects on the quiet geomagnetic field


  • S. Matsushita,

  • J. D. Tarpley,

  • W. H. Campbell


A correlation of the interplanetary magnetic field sector structures including the east-west component with the polar geomagnetic field variations has recently been suggested by several scientists. To clarify the details of the correlation and to facilitate discussion of the physical mechanism involved in the interaction, 2.5-min digitized geomagnetic data from 40 stations located from the northern polar cap through the southern subauroral zone are examined during quiet days in 1965. The Sqp equivalent overhead current systems are investigated with respect to seasonal changes and variations corresponding to toward- and away-sector structures by the technique of spherical harmonic expansions of the data. In addition to obvious seasonal variations of the Sqp, a clear shift of the average Sqp pattern toward the afternoon (early morning) side of the polar cap for the toward-sector (away-sector) structure is obtained. Furthermore, small but remarkable sector effects on the quiet geomagnetic field in middle and low latitudes are discovered. The results of this work contribute to the discussion of sector structure effects on magnetic field merging at the magnetopause and convective patterns in the magnetosphere.