On the energy of the poloidal magnetic field near the ionosphere

概要

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The role of the ionospheric Hall effect on the energy balance in the magnetosphere-ionosphere (MI) system coupled through the field-aligned current (FAC) is discussed. FACs lose their stored electromagnetic energy in the ionosphere through Joule dissipation; this process is caused by the closure of the FAC via the ionospheric Pedersen current carried by ions. On the other hand, the ionospheric rotational Hall current carried by electrons cannot be dissipated. However, the ionospheric rotational Hall current can also be excited by an incident FAC, causing it to radiate Poynting fluxes that lead to the growth of a poloidal-type magnetic field in the magnetosphere and atmosphere. From the viewpoint of energy conservation, a few ambiguities in the above statements may be recognized. In this paper, we clarify the energy balance of the electromagnetic disturbances between the magnetosphere, ionosphere and atmosphere. The generation of the Hall current (together with the associated poloidal magnetic field) will be shown to occur during the growth stage, when the electromagnetic energy is pumped through the divergent Hall current, regardless of how slow the growth may have been.
国立極地研究所の論文