The interplanetary magnetic field structure

Abstract

The seasonal bias in the sector structure of the interplanetary magnetic field has led to the suggestion that the field in each hemisphere of the solar cavity has the same polarity as the average magnetic field at the corresponding solar pole, and that the surface which separates the two polarity regions is only slightly warped. In this scheme the observed sector structure results from corotation of the warped surface past the earth with the angular velocity of the sun. This picture of the interplanetary field structure provides a simple explanation for the solar magnetic cycle periodicity of the diurnal variation of energetic cosmic rays. A discrepancy between the large latitudinal extent of the photospheric sector structure and the apparently small extent of the interplanetary sector structure places constraints on models of the origin of the solar wind. The discrepancy can be resolved if the solar wind originates high in the solar atmosphere where the geometry of the interplanetary field is simplified by magnetic stresses, or if coronal holes produce a large portion of the solar wind.