Mesoscale and large-scale variability in high-latitude ionospheric convection: Dominant modes and spatial/temporal coherence

Dominant modes of ionospheric electric field variability are identified and the spatial and temporal coherence of this variability is quantified. The first three modes of variability, which, together with the mean, account for ∼50% of the observed squared electric field (E²), are characterized by global spatial scales and long time scales (∼1 h).

The first and second modes of variability represent the strengthening/weakening of the global convection pattern and the shaping of the convection pattern into asymmetrical round- and crescent-shaped cells. These two modes are correlated with the Bz and By components of the interplanetary magnetic field. The third mode represents the expansion/contraction of the convection pattern and is weakly correlated with the solar wind velocity.