Ionospheric outflow supplies nearly all of the heavy ions observed within the magnetosphere, as well as a significant fraction of the proton density. While much is known about upflow and outflow energization processes, the full global pattern of outflow and its evolution is only known statistically or through numerical modeling. Because of the dominant role of heavy ions in several key physical processes, this unknown nature of the full outflow pattern leads to significant uncertainty in understanding geospace dynamics, especially surrounding storm intervals. That is, global models risk not accurately reproducing the main features of intense space storms because the amount of ionospheric outflow is poorly specified and thus magnetospheric composition and mass loading could be ill-defined. This study defines a potential mission to observe ionospheric outflow from several platforms, allowing for a reasonable and sufficient reconstruction of the full outflow pattern on an orbital cadence. An observing system simulation experiment is conducted, revealing that four well-placed satellites are sufficient for reasonably accurate outflow reconstructions. The science scope of this mission could include the following: reveal the global structure of ionospheric outflow; relate outflow patterns to geomagnetic activity level; and determine the spatial and temporal nature of outflow composition. The science objectives could be focused to be achieved with minimal instrumentation (only a low-energy ion spectrometer to obtain outflow reconstructions) or with a larger scientific scope by including contextual instrumentation. Note that the upcoming Geospace Dynamics Constellation mission will observe upwelling but not ionospheric outflow.

Despite significant developments in global modeling, the determination of ionospheric conductance in the auroral region remains a challenge in the space science community. With advances in adiabatic kinetic theory and numerical couplings between global magnetohydrodynamic models and ring current models, the dynamic prediction of individual sources of auroral conductance have improved significantly. However, the individual impact of these sources on the total conductance and ionospheric electrodynamics remains understudied. In this study, we have investigated individual contributions from four types of auroral precipitation - electron & ion diffuse, monoenergetic & Alfven wave-driven - on ionospheric electrodynamics using a novel modeling setup. The setup encompasses recent developments within the University of Michigan’s Space Weather Modeling Framework (SWMF), specifically through the use of the MAGNetosphere - Ionosphere - Thermosphere auroral precipitation model and dynamic two-way coupling with the Global Ionosphere-Thermosphere Model. This modeling setup replaces the empirical idealizations traditionally used to estimate conductance in SWMF, with a physics-based approach capable of resolving 3-D high-resolution mesoscale features in the ionosphere-thermosphere system. Using this setup, we have simulated an idealized case of southward Bz 5nT & the April 5-7 “Galaxy15” Event. Contributions from each source of precipitation are compared against the OVATION Prime Model, while auroral patterns and hemispheric power during Galaxy15 are compared against observations from DMSP SSUSI and the AE-based FTA model. Additionally, comparison of field aligned currents (FACs) and potential patterns are also conducted against AMPERE, SuperDARN & AMIE estimations. Progressively applying conductance sources, we find that diffuse contributions from ions and electrons provide ~75% of the total energy flux and Hall conductance in the auroral region. Despite this, we find that Region 2 FACs increase by ~11% & cross-polar potential reduces by ~8.5% with the addition of monoenergetic and broadband sources, compared to <1% change in potential for diffuse additions to the conductance. Results also indicate a dominant impact of ring current on the strength and morphology of the precipitation pattern.

Conductivity of the ionosphere allows the complex system of magnetospheric currents to flow through. Conductivity is governed by several factors including electron density and temperature, whose influence is highly dynamic during geomagnetic storm events. Thus, it is a crucial parameter that must be determined for space weather modeling to specify the coupling between the magnetosphere, ionosphere and thermosphere systems. Major sources of ionospheric conductivity are solar EUV and particle precipitation which includes Diffuse (Diff.), Monoenergetic (ME) and Broadband (BB) precipitations. Conductance Σ is the height integrated version of conductivity. Empirically, total ionospheric conductance (Hall and Pedersen) is known to be the root sum square of individual conductance terms [Wallis and Budzinski, 1981], considering that conductivity resulting from different processes are not linearly additive and corresponding ionization rates shall be added at each altitude and then integrated over the desired altitude range. With the inclusion of the less energetic broadband precipitation that was found to cause ionization in the bottom-side F region, the expression for the total ionospheric conductance was modified by the linear addition of the contribution of the broadband precipitation to the total Hall and Pedersen conductance[Zhang et al., 2015].In this study, using a 3-dimensional global physics based model GITM (Global Ionosphere Thermosphere Model), the validity of this combination of vector and linear addition of individual source terms to the total ionospheric conductance is examined and the more accurate expression for the summation of sources contributing to the total conductance is quantified. GITM is employed to calculate the Hall and Pedersen conductance using the average energy, potential and energy flux for each of the sources of conductance. Several scenarios are simulated where the different sources of precipitation are paired with solar EUV radiation, and the total conductance is obtained. Linear and vector summation of conductance resulting from combinations of sources and individual sources indicate that the contribution of broadband precipitation to the total conductance also follows vector addition. To quantify the result that the total conductance is the vector sum of individual sources, error histograms are plotted and a set of metrics including RMSE, mean error, standard deviation, correlation coefficient and fractional error are enumerated for both linear and vector summation of individual sources to produce the total conductance.