Synthesis models of dayside field-aligned currents for strong interplanetary magnetic field by

Using particle and magnetic field data acquired with DMSP-F6 and DMSP-F7 satellitesw, e have investigatedin terplanetarym agneticf ield (IMF) By dependenceo f the globalp attern of plasmar egime and field-alignedc urrents(FACs) on dayside high latitudes during strong IMF By (averaged |By| > 3.7 nT) andg eomagneticadllyis turbed (mainly IMF Bz < 0) periods. From particle data we have identified five plasma regimes: inner plasma sheet, outer plasma sheet, cleft, cusp, and mantle. All the plasma domains exceptt he inner plasmas heets howB y dependencein spatiald istribution.R egion 1 and “traditional cusp” currents appear in cusp/mantle domains, which we call midday region 1 and region 0 currents, r espectivelyi,n this paper. These currentsp erfectlyr everset heir flow directions depending on IMF By polarity. Traditional region 1 currents occurring in cleft and outer plasma sheet almost always flow into the ionosphere in the prenoon sector and flow awayf rom the ionospherein the postnoons ectorr egardlesso f By polarity. Thus the midday region 1 and region 0 current system that appears at local noon is not a simple continuation of flankside region 1/region 2 current system. Midday region 1 and region 0 currentsa re not necessarilyb alancedi n intensity;r egion 0 current intensityo ccasionally exceeds midday region 1 current intensity. Furthermore, intensity imbalance also appears in cleft-associatedre gion 1 currents;t hat is, region 1 current in the farside cleft from the reconnections ite (“downstreamsidec”l eft) is larger than region 1 current in the nearside cleft (“upstreamsidec” left). On the basiso f theseo bservationafla ctsw e discussth e sourcem echanismos f the daysideF AC system(1) directlyc oupledg enerationo f region0 and midday region 1 current in the cusp/mantle domainsa round noon and (2) generation of extra region 0 current in the tail magnetopausew hich is connectedt o the extra downs treamside cleft-associated region 1 current.