optical observations at 557.7 nm have been successfully
used to produce all-sky maps of Pedersen conductance. The method was
calibrated using EISCAT data at one point and then applied to the
field of view of 520x520 km. The technique worked
well because Pedersen conductance and the 557.7 nm optical
emission both maximise in the E-region. However, the electrojet, which
constitutes a major portion of the total ionospheric current, is a
Hall current occurring at lower altitudes. The strength and direction
of currents is determined by the temporal and spatial morphology of
the conductance distribution. Since the Hall conductance maximises at
lower altitudes than Pedersen conductance, it is much more dependent
on the energy of the precipitating particles. Hence it is essential
that multi- wavelength observations (e.g., 427.8 and 557.7 nm) be
used to determine the energy- dependent component of the particle
precipitation producing the Hall conductance. All-sky maps of Hall
conductance, in additional to Pedersen conductance, are important
since they will facilitate the study of ionospheric currents, which
constitute an integral part of the magnetic field-aligned currents
coupling the ionosphere to the magnetosphere.
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