Abstract
Lobe reconnection is usually thought to play an important role in
geospace dynamics only when the Interplanetary Magnetic Field (IMF) is
mainly northward. This is because the most common and unambiguous
signature of lobe reconnection is the strong sunward convection in the
polar cap ionosphere observed during these conditions. During more
typical conditions, when the IMF is mainly oriented in a dawn-dusk
direction, plasma flows initiated by dayside and lobe reconnection both
map to high latitude ionospheric locations in close proximity to each
other on the dayside. This makes the distinction of the source of the
observed dayside polar cap convection ambiguous, as the flow magnitude
and direction are similar from the two topologically different source
regions. We here overcome this challenge by normalizing the ionospheric
convection observed by the Super Dual Aurora Radar Network (SuperDARN)
to the polar cap boundary, inferred from simultaneous observations from
the Active Magnetosphere and Planetary Electrodynamics Response
Experiment (AMPERE). This new method enable us to separate and quantify
the relative contribution of both lobe reconnection and
dayside/nightside (Dungey cycle) reconnection during periods of
dominating IMF By. Our main findings are twofold. First, the lobe
reconnection rate can typically account for 20% of the Dungey cycle
flux transport during local summer when IMF By is dominating and IMF Bz
> 0. Second, the dayside convection relative to the
open/closed boundary is vastly different in local summer versus local
winter, as defined by the dipole tilt angle.