Substorm currents and Cowling channels

Abstract:

The talk will give a brief overview of the magnetosphere-ionosphere (M-I) coupling during substorms seen in the ionosphere, particularly that of the distributions of macro- and meso-scale field-aligned currents (FACs), auroras and associated electrodynamic parameters such as the electric field and the ionophseric conductance. These physical quantities are adjusted to each other spatially and temporarily in a physically consistent manner, which is the essence of the M-I coupling. The Cowling channel mechanism first invented in connection with the solar atmosphere is one of the most fundamental processes of the M-I coupling, describing which extent the divergence of the Hall current at the inhomogeneity of the Hall conductance can be connected to the Pedersen current with producing excess space charges and hence polarization electric field (ionospheric closure) or to FACs flowing into/from the magnetosphere (magnetospheric closure). The talk will show extensive efforts to understand the Cowling channel mechanism and to determine the ratio between the amounts of the two closure currents, and its applications to the substorm currents and pulsating auroras.