HR: 15:10h
AN: SM52D-06    [PDF]
TI: New Terminology for the High-Latitude Field-Aligned Current Systems
AU: * Papitashvili, V
EM: papita@umich.edu
AF: SPRL, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109 United States
AU: Weimer, D
EM: dweimer@mrcnh.com
AF: Mission Research Corporation, 589 West Hollis St., Suite 201, Nashua, NH 03062 United States
AB: Since pioneering works of Iijima and Potemra in mid-1970s, the lexical meaning of terms Region 1 and Region 2 have formulated a definitive lexicon for describing the field-aligned currents systems linking the outer and inner magnetosphere with both the northern and southern polar ionospheres. However, the Region 0 system remains problematic in its clear detection or definition; at the same time, the NBZ FAC system has been easily accepted for describing of reverse (to R1) currents at the near-pole dayside developed during the northward IMF. The separate IMF ${\rm B{_y}}$-related FAC configurations were either observed by satellites or reconstructed from ground-based data for the dayside cusp region; multi-sheet current systems were proposed for the nightside polar area. Although it seems that these lexical elements were sufficient in describing various components of the global 3-D FAC systems, a number of recent studies utilized high-precision satellite magnetic field measurements for deriving detailed FAC polar maps as a function of the IMF strength and direction. The basic R1/R2 and NBZ patterns are seen, but the maps show structures that are more complex and evolving as the IMF vector rotates. In addition, a potentially new FAC system is detected from statistical maps for $\rm IMF \sim 0$, having the same current directions as NBZ. This system might be considered as a part of the R0 system; from the other hand, what might be considered as a R1 current footprint often wraps around, through noon or midnight, connecting with either R2 or R0 currents (when IMF By is either negative or positive, respectively) without any obvious boundary line. Interestingly, the new statistical maps show features resembling the ``upward current spiral'' and ``downward current spiral'' introduced by {\it Siscoe and Maynard} [JGRA, {\it 96}, 21,071, 1991] from combining two theoretical models of R1 and R2 currents. These spirals ``rotate'' over the polar cap showing R0, R1, and R2 segments at the corresponding MLT hours. We will discuss new terms that might be needed for the existing lexicon - to extend its old terminology in describing the modern understanding of morphology and evolution of the high-latitude field-aligned current systems.
UR: http://maggy.engin.umich.edu/mist/limie.html
DE: 2409 Current systems (2708)
DE: 2411 Electric fields (2712)
DE: 2463 Plasma convection
DE: 2708 Current systems (2409)
DE: 2712 Electric fields (2411)
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting