We describe the achievement of a significant step in a program whose u
ltimate goal is a self-consistent model that matches cusp currents fro
m both ionospheric and magnetospheric sources. Building on existing mo
dels, we calculate currents that arise from the ionosphere's ohmic res
ponse to the interplanetary electric field mapped to the polar cap. Un
like other models, the mapping is confined to the vicinity of the cusp
, simulating limited direct communication with the solar wind, as mand
ated by recent observations. The mapped area is then inserted into the
dayside gap of a purely ionospheric expanding polar cap model. The re
sulting two-cell convection patterns have a pronounced kink in the ant
isunward flow contours at the poleward boundary of the cusp area, wher
e it joins the expanding polar cap. A similar kink appears in the Hepp
ner-Maynard empirical patterns; the model implies that it marks the bo
undary where the ionosphere takes control from the solar wind. The mod
el serves as a first tool for identifying Birkeland current types and
causes. Three types arise: (1) Currents border the open cusp like regi
on 1 currents bordering a steady state, mini-polar cap. (2) Within the
cusp, currents arise from curvature of the equipotentials which, when
mapped to the magnetopause, correspond to flow directed away from the
merging line, representing merging outflow. (3) The usual region 1 cu
rrents line the polar cap boundary along the flow reversals of the two
convection cells as a result of polar cap expansion; they are the ion
ospheric response to the applied electric field. Thus the model predic
ts two types of region 1 currents, driven directly (1) and indirectly
(3) by the solar wind, plus a set of pure cusp currents (2). Together
they form the familiar overlapping pattern in the cusp region deduced
from observations.