title: Sector Structure of the Quiet Interplanetary Magnetic Field.
abstract: Observations of the interplanetary magnetic field by the Imp-1 satellite have revealed a regular longitudinal sector structure in this field. The sectors co-rotate with the sun; as an average sector sweeps past the earth the magnitude of the interplanetary field decreases from greater than 6 gammas (1 gamma = 10(-5) gauss) to less than 4 gammas, and the daily sum of the geomagnetic activity index, Kp, decreases from 25 to less than 10.
authors.forename: N F
authors.initials: NF
authors.lastname: Ness
authors.forename: J M
authors.initials: JM
authors.lastname: Wilcox