The neutral wind “flywheel” as a source of quiet‐time, polar‐cap currents

The neutral wind pattern over the summer polar cap can be driven by plasma convection to resemble the convection pattern. For a north‐south component of the interplanetary magnetic field B z directed southward, the wind speeds in the conducting E‐region can become ∼ 25% of the electric field drift speeds. If convection ceases, this neutral wind distribution can drive a significant polar cap current system for ∼ 6 hours. The currents are reversed from those driven by the electric fields for southward B z , and the Hall and field‐aligned components of the current system resemble those observed during periods of northward B z . The current magnitudes are similar to those observed during periods of small, northward B z ; however observations indicate that electric fields often contribute to the currents as much as, or more than, the neutral winds.