Dartmouth Events

Abstract: The magnetosphere-ionosphere/thermosphere-ground coupling takes place in full strength in the polar region where momentum and energy mostly propagate from the magnetosphere along the magnetic field down and drive the polar ionospheric and thermospheric motions and eventually to the ground. Some of the energy is dissipated in the ionosphere/thermosphere and remaining drives the motion in lower latitudes. In the ionosphere/thermosphere, this system is a partially ionized gas with ionization fraction changing from nearly unity to near zero with strong collisions between plasma and neutral particles. This coupling of the system has been treated as in steady state because when including the dynamic effects, the mathematic and/or numerical issues become extremely challenging. The coupling from the ionosphere/thermosphere to the ground has not been treated adequately. Our group has been successful in solving the problem globally in 2-D numerically, which helps us to understanding the physical processes involved. I will present a physical model to describe the key processes governing the coupling in this talk, which merges the conventional space physics and optics approaches. The most important and surprising conclusion is that coupling from the lower ionosphere to the ground is not electrostatic but magnetic static, casting doubts on any treatment and mechanism that describes the coupling based on an assumption of static electric field or potential.