  Statistical analyses have shown that the sunward component of the
interplanetary magnetic field, $\mathit{B}_{x}$ (Geocentric Solar
Magnetospheric), moderately but significantly affects the auroral intensity.
These observations have been interpreted as signatures of a similar
interplanetary magnetic field $\mathit{B}_{x}$ control on Birkeland currents
yet to be observed directly. Such a control, attributed to differences in
magnetic tension on newly opened magnetic field lines, would lead to stronger
region 1 (R1) Birkeland currents for $\mathit{B}_{x}$ negative (positive)
conditions in the Northern (Southern) Hemispheres than when $\mathit{B}_{x}$ is
positive (negative). In this paper we perform a detailed investigation of three
different sets of magnetic field measurements, from the Challenging
Minisatellite Payload and Swarm low Earth orbit satellites, from the Active
Magnetosphere and Planetary Electrodynamics Response Experiment products
derived from the Iridium satellite constellation, and from the SuperMAG ground
magnetometer network, each analyzed using different techniques, to test these
predictions. The results show that a change in sign of $\mathit{B}_{x}$ changes
the Birkeland currents by no more than $\approx$10%. The current patterns show
little support for an interhemispheric asymmetry of the kind proposed to
explain auroral observations. Instead, we propose an alternative
interpretation, which is consistent with most of the auroral observations and
with the current observations in the present paper, except for those based on
Active Magnetosphere and Planetary Electrodynamics Response Experiment: The
solar wind-magnetosphere coupling is more efficient when the dipole tilt angle
and $\mathit{B}_{x}$ have the same sign than when they are different...
(continued on
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JA024864)
