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Abstract We investigated the effects of storm‐time diffuse auroral electron precipitation on ionospheric Pedersen and Hall conductivity and conductance during the CME‐driven St. Patrick's Day storms of 2013 (minDst = −131 nT) and 2015 (minDst = −233 nT). These storms were simulated using the magnetically and electrically self‐consistent RCM‐E model with STET modifications, alongside the B3C auroral transport code to compute ionospheric conductivities and height‐integrated conductance. The simulation results were validated against conductance inferred from Poker Flat Incoherent Scatter Radar (PFISR) and Millstone Hill Incoherent Scatter Radar (MHISR) measurements. Our simulations show that the magnetic latitude and local time distribution of Pedersen and Hall auroral conductance strongly correlate with diffuse electron precipitation flux, with the plasmapause marking the low‐latitude boundary of conductance. Simulated Pedersen/Hall conductance agrees reasonably well with PFISR measurements at 65.9° MLAT during diffuse auroral precipitation. During the intense 2015 storm, diffuse aurora extended down to 52.5° MLAT, with simulated conductance agreeing within a factor of two with MHISR observations. Discrete auroral arcs observed during both storms enhanced PFISR conductance by tens of siemens, though these enhancements were not captured by the model. Additionally, the simulated electric intensity showed development of sub‐auroral polarization streams (SAPS) and dawn SAPS features and followed the general trend of Poker Flat electric intensity at 65.9° MLAT during diffuse aurora, despite being updated every 5 min. The overall agreement between simulated ionospheric conductance and electric intensity with observations highlights the model's capability during diffuse auroral precipitation. 

An important question that is being increasingly studied across subdisciplines of Heliophysics is “how do mesoscale phenomena contribute to the global response of the system?” This review paper focuses on this question within two specific but interlinked regions in Near-Earth space: the magnetotail’s transition region to the inner magnetosphere and the ionosphere. There is a concerted effort within the Geospace Environment Modeling (GEM) community to understand the degree to which mesoscale transport in the magnetotail contributes to the global dynamics of magnetic flux transport and dipolarization, particle transport and injections contributing to the storm-time ring current development, and the substorm current wedge. Because the magnetosphere-ionosphere is a tightly coupled system, it is also important to understand how mesoscale transport in the magnetotail impacts auroral precipitation and the global ionospheric system response. Groups within the Coupling, Energetics and Dynamics of Atmospheric Regions Program (CEDAR) community have also been studying how the ionosphere-thermosphere responds to these mesoscale drivers. These specific open questions are part of a larger need to better characterize and quantify mesoscale “messengers” or “conduits” of information—magnetic flux, particle flux, current, and energy—which are key to understanding the global system. After reviewing recent progress and open questions, we suggest datasets that, if developed in the future, will help answer these questions.