The effect of the east‐west component of the interplanetary magnetic field on magnetospheric convection as deduced from magnetic perturbations at high latitudes

The variations of the horizontal and vertical components of the ground magnetic field at high latitudes are analyzed in order to separate the perturbations related to the east-west component By of the interplanetary magnetic field from other perturbations. At invariant latitude Λ ≳ 80° the perturbations of the vertical component are characterized by a daytime extremum that is maximum when By is negative and minimum when By is positive. This effect becomes inverted when Λ ≲ 80° and disappears when Λ ≲ 75°. The currents that are equivalent to the additional horizontal perturbations due to the orientation of By are maximum on the day side and follow a rather circular flow pattern, which in the southern hemisphere is westward in the case where By is positive and eastward in the case where By is negative. In the northern hemisphere these average directions are reversed symmetrically. An asymmetric magnetospheric convection pattern may be deduced from these results.