Extensive three-dimensional computer simulations of the magnetosphere-ionosphere (M-I) coupling are performed to study self-excitation of an auroral arclike structure with special emphasis on (1) nonlinear evolution of the feedback instability in the M-I coupling system, (2) controlling mechanisms of the arc structure, (3) formation of a field-aligned electric potential structure in association with the development of the feedback instability, and (4) effects of the parallel potential generation on the development of the arclike structure. The present study takes the first step toward the theoretical understanding of the M-I coupling system with parallel potentials. As was already shown by Sato [1978> and Watanabe and Sato [1988>, it is reconfirmed that the feedback instability produces a longitudinally elongated, latitudinally striated structure where the upward field-aligned current and the ionospheric density are locally enhanced. On top of this the present extended study reveals the following important new features: The global distribution of the striation structure is primarily governed by the magnetospheric convection pattern and the ionospheric density distribution. There appears a significant dawn-dusk asymmetry in the arc formation, even though the apparent geometrical relationship is symmetric.

This dawn-dusk asymmetry reflects the geometrical fact that the ionospheric Pedersen current closing the magnetospheric current is antisymmetric with respect to the noon-midnight plane, while the self-closed Hall current is symmetric. The recombination effect plays a significant role in the global, as well as local, development of the arc structure. The nonlinearity of recombination, in conjunction with the closure of an arc-associated local field-aligned current system, acts to destroy an old arc and creates a new arc in a different but adjacent position. This results in a peculiar dynamic evolution of the arclike structure. A V-shaped field-aligned potential structure is created in association with an arc structure, when we introduce the parallel anomalous resistivity. The nonlinear phase mismatching due to the parallel resistivity reduces the growth rate of the feedback instability, and suppresses the growth of the arc structure. When the effect of precipitating hot electrons is taken into account, the ionospheric density is considerably enhanced locally at the foot of the field lines where the field-aligned potential is generated. An oscillatory behavior is observed in the development of the ionospheric density, field-aligned current, and potential. The period seems to be governed by the Alfv¿n bounce time and the ionospheric density. ¿ American Geophysical Union 1993