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Electron density irregularities in the ionosphere can give rise to scintillations, affecting radio wave phase and amplitude. While scintillations in the cusp and polar cap regions are commonly associated with mesoscale density inhomogeneities and/or shearing, the auroral regions exhibit a strong correlation between scintillation and density structures generated by electron precipitation (arcs). We aim to examine the impact of electron precipitation on the formation of scintillation‐producing density structures using a high‐resolution physics‐based plasma model, the "Geospace Environment Model of Ion‐Neutral Interactions," coupled with a radio propagation model, the "Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere." Specifically, we explore the effects of varying spatial and temporal characteristics of the precipitation, including electron total energy flux and their characteristic energies, obtained from the all‐sky‐imagers and Poker Flat Incoherent Scatter Radar observations, on auroral scintillation. To capture small‐scale structures, we incorporate a power‐law turbulence spectrum that induces short wavelength features sensitive to scintillation. Finally, we compare our simulated scintillation results with satellite‐observed scintillations, along with spectral comparisons. Key Points: A physics‐based plasma model and a radio propagation model are used to examine the effects of precipitation on auroral scintillationPrecipitation fluxes with higher energy, a turbulent noise spectrum, and a faster‐moving arc intensify scintillationThe presence of small‐scale precipitation amplifies both phase and amplitude scintillations [ABSTRACT FROM AUTHOR]

Space‐based observations of the signatures associated with STEVE show how this phenomenon might be closely related to an extreme version of a SAID channel. Measurements show high velocities (>4 km/s), high temperatures (>4,000 K), and very large current density drivers (up to 1 μA/m2). This phenomena happens in a small range of latitudes, less than a degree, but with a large longitudinal span. In this study, we utilize the GEMINI model to simulate an extreme SAID/STEVE. We assume a FAC density coming from the magnetosphere as the main driver, allowing all other parameters to adjust accordingly. We have two main objectives with this work: show how an extreme SAID can have velocity values comparable or larger than the ones measured under STEVE, and to display the limitations and missing physics that arise due to the extreme values of temperature and velocity. Changes had to be made to GEMINI due to the extreme conditions, particularly some neutral‐collision frequencies. The importance of the temperature threshold at which some collision frequencies go outside their respective bounds, as well as significance of the energies that would cause inelastic collisions and impact ionization are displayed and discussed. We illustrate complex structures and behaviors, emphasizing the importance of 3D simulations in capturing these phenomena. Longitudinal structure is emphasized, as the channel develops differently depending on MLT. However, these simulations should be viewed as approximations due to the limited observations available to constrain the model inputs and the assumptions made to achieve sensible results. Key Points: We present a full 4D (3D + time) simulation of an extreme SAIDWe utilize the GEMINI model for the simulation due to the practicality and easiness to set arbitrary input files. Though challenges remainWe highlight the importance of inelastic collisions and impact ionization on damping the channel velocity, physics not included in GEMINI [ABSTRACT FROM AUTHOR]

Solar-terrestrial interactions produce a rich variety of optical emissions in the Earth's upper atmosphere (100-1000 km). While ground based brightness measurements (i.e., column integrated photon density) provide an important diagnostic of these processes, the more interesting physics is in the associated volume emission rate distribution (i.e., photon production/[cm.sup.3] s versus altitude). This work examines a new technique for remote sensing of the Earths' radiative environment. Brightness measurements from a network of ground-based imaging systems are used to define a limited angle emission tomography problem, from which two-dimensional (2-D) (latitude versus altitude) volume emission rate profiles are reconstructed. The incomplete angular coverage imposed by this viewing geometry leads to an ill-posed and ill-conditioned inverse problem. The problem is regularized by initially constraining the vertical profiles to be Chapman functions. Such a parameterization captures the mean features of a large class of emission structures. A weighted Euclidean distance between the measured and estimated data is then minimized, subject to side constraints that define the feasibility region for the Chapman parameters. The side constraints are implemented as barrier functions, resulting in an unconstrained nonlinear optimization problem. Minimization is performed using the Broyden-Fletcher-Goldfarb-Shanno variant of the Davidon-Fletcher-Powell (DFP) method. The resulting volume emission rate elements are then used as an initial guess to a multiplicative algebraic reconstruction (MART) algorithm. In addition to regularizing the problem, this technique exposes important geometrical limitations to this class of inverse problem. Index Terms - Airglow, aurora, ionosphere, nonlinear optimization, tomography.