The dependence of the strength and thickness of field-aligned currents on solar wind and ionospheric parameters

摘要

abstract_textpSheared plasma flows at the low-latitude boundary layer (LLBL) correlate well with early afternoon auroral arcs and upward field-aligned currents. We present a simple analytic model that relates solar wind and ionospheric parameters to the strength and thickness of field-aligned currents (Lambda) in a region of sheared velocity, such as the LLBL. We compare the predictions of the model with DMSP observations and find remarkably good scaling of the upward region 1 currents with solar wind and ionospheric parameters in region located at the boundary layer or open field lines at 1100-1700 magnetic local time. We demonstrate that Lambda similar to n(sw)(-0.5) and Lambda similar to L when Lambda/L 5 where L is the auroral electrostatic scale length. The sheared boundary layer thickness (Delta(m)) is inferred to be around 3000 km, which appears to have weak dependence on V-sw. J(parallel to) has dependencies on Delta(m), Sigma(p), n(sw), and V-sw. The analytic model provides a simple way to organize data and to infer boundary layer structures from ionospheric data./p/abstract_text