Examining the Auroral Ionosphere in Three Dimensions Using Reconstructed 2D Maps of Auroral Data to Drive the 3D GEMINI Model

Abstract

We use the Geospace Environment Model of Ion‐Neutral Interactions (GEMINI) to create three‐dimensional, time‐dependent simulations of auroral ionospheric parameters in the localized, several 100 km region surrounding auroral arcs observed during a winter 2017 sounding rocket campaign, resolving three‐dimensional features of fine‐scale (km) flow structures in the vicinity of an auroral arc. The three‐dimensional calculations of GEMINI allow (with sufficient driving data) auroral current closure to be investigated without idealizing assumptions of sheet‐like structures or height integrated ionospheres. Datamaps for two nearly sheet‐like arcs are reconstructed from replications of the Isinglass sounding rocket campaign data, and combined with camera‐based particle inversions into a set of driving inputs to run the 3D time‐dependent model. Comparisons of model results to radar density profiles and to in situ magnetometry observations are presented. Slices of volumetric current, flow, and conductance structures from model outputs are used to interpret closure currents in an auroral arc region, and are compared to original in situ measurements for verification. The predominant source of return current region field aligned current closure for these slow time variation events is seen to be from the conductance gradients, including the Hall. The importance of the ∇normalΣH versus ∇normalΣP terms in the determination of the current structure provides a more complicated picture than a previous GEMINI study, which relied predominantly on the divergence of the electric field to determine current structure. Sensitivity of data‐driven model results to details of replication and reconstruction processes are discussed, with improvements outlined for future work.

An Ionospheric Conductance Gradient Driver for Subauroral Picket Fence Visible Signatures Near STEVE Events

“…The various panels are described in the first caption. Notice the stronger FACs generated by the Nishimura run (Figure 4), well exceeding the ∼10 μA/m 2 or more current density often seen in sounding rocket observations (Clayton et al, 2021; , 2012, 2015) of rayed or otherwise structured auroral curtains which are interpreted as signatures of tearing mode instabilities (Seyler, 1990). This strong model-run current sheet is colocated with a strong pinching of the low-altitude plasma density just poleward of the equatorward flow structure.…”

Local Mapping of Polar Ionospheric Electrodynamics

“…The third term, which describes the divergence of Hall currents as they flow across gradients in Σ H is small in this case. This separation may be relevant to get further insights into the what controls the morphology of the ionospheric current system (Clayton et al., 2021 ). We emphasize that a realistic conductance must be provided to perform a reliable decomposition of the FACs.…”

“…The Lompe technique could also be useful to increase the utility of certain measurements, such as multispectral imaging from GBOs (Clayton et al., 2019 , 2021 ; Grubbs et al., 2018 ) and data from phased array incoherent scatter radars. For example, the EISCAT3D radar system (McCrea et al., 2015 ), which will be operational soon, will give ion flow measurements and ionospheric density in a volume above the field of view of the measurement sites.…”

Local Mapping of Polar Ionospheric Electrodynamics

“…The Lompe technique could also be useful to increase the utility of certain measurements, such as multispectral imaging from GBOs (Clayton et al, 2019(Clayton et al, , 2021Grubbs et al, 2018) and data from phased array incoherent scatter radars. For example, the EISCAT3D radar system (McCrea et al, 2015), which will be operational soon, will give ion flow measurements and ionospheric density in a volume above the field of view of the measurement sites.…”

“…The third term, which describes the divergence of Hall currents as they flow across gradients in Σ H is small in this case. This separation may be relevant to get further insights into the what controls the morphology of the ionospheric current system (Clayton et al, 2021). We emphasize that a realistic conductance must be provided to perform a reliable decomposition of the FACs.…”