We demonstrate scintillation analysis from a network of geodetic Global Positioning System (GPS) receivers which provide data at 1-second resolution. We introduce proxy phase ($\sigma_{TEC}$) and amplitude ($SNR_4$) scintillation indices and validate them against the rate of change of TEC index (ROTI), and $S_4$. Additionally, we validate scintillation observations against a CASES scintillation receiver. We develop receiver dependent scintillation event thresholding using hardware-dependent noise variance. We analyze six-days adjacent to the 7-8 September 2017 geomagnetic storm, using 169 receivers covering magnetic latitudes between 15$^\circ$ and 65$^\circ$ in the American longitude sector. We leverage the available spatial sampling coverage to construct 2-D maps of scintillation and present episodic evolution of scintillation intensifications during the storm. We show that low-latitude and high-latitude scintillation morphology match well-established scintillation climatology patterns. At mid-latitudes, spatiotemporal evolution of scintillation partially agrees with known scintillation patterns. Additionally, the results reveal previously undocumented mid-latitude scintillation producing structures. The results provide an unprecedented view into the spatiotemporal development of scintillation-producing plasma irregularities and provide a resource to further exploit scintillation evolution at large spatial scales.

We report on an extreme ionospheric plasma density enhancement and Global Positioning System (GPS) scintillation at dawn, observed within the expanding equatorial ionization anomaly (EIA). The total electron content (TEC) in central America reached 50~TECu at sunrise, the value almost twice as high as the normal afternoon peak. The enhanced EIA expanded poleward and westward from just below 20$^\circ$ magnetic latitude (MLAT) to beyond 30$^\circ$ MLAT at sunrise. The chief ramification of the enhanced EIA was strong GPS scintillation which was observed poleward of 30$^\circ$ northern MLAT and lasted until 8:00 local time. In total, the scintillation lasted for $\sim$5~hours at latitudes north of 20$^\circ$MLAT in central America.

The main ionospheric trough (MIT) is a salient density feature in the mid-latitude ionosphere and characterizing its structure is important for understanding GPS and HF signal propagation, and identifying geospace phenomena such as the plasmapause boundary layer. While a number of previous studies have statistically investigated the properties of the MIT utilizing low-altitude satellite observations, they have been limited to latitudinal cross sections, and have not considered the inherent two-dimensional structure of the trough. In this work, we develop a regularized inversion method for identifying the two dimensional structure of the trough in Total Electron Content (TEC) maps. Because no ground truth labels exist for the MIT, we extensively characterize the behavior of the algorithm by comparing it to the method developed by \citeA{aa-2020}. We show that statistics computed on the resulting labels are robust to our choice of algorithm parameters and that we are able to match the results of \citeA{aa-2020} with a particular selection of the parameters. Without ground truth, these two properties provide much stronger verification than a comparison using a single parameter setting. In addition to enabling fundamentally different studies, our MIT labels are able to provide statistical MIT properties with higher resolution.

Solar eclipses cause profound effects on ionosphere-thermosphere dynamics due to the abatement of solar Extreme Ultra Violet (EUV) irradiance. The reduced EUV flux cause relative reduction of ionospheric plasma density and temperature, and well as it reduces thermospheric temperature, and alters neutral winds. Numerical simulations are used to understand and characterize the ionosphere-thermosphere response to solar eclipses and to compare the model results with observations. The models have traditionally implemented simplified solar eclipses, assuming spherically symmetric models with the maximum eclipse (obscuration) set to ~15%. We present a realistic model of solar eclipses, using Solar Dynamic Observatory (SDO) Atmospheric Imaging Assembly (AIA) images of the solar corona. This model computes the eclipse occultation factors as a function of geolocation and time for a chosen SDO AIA wavelength. The model includes an interface to retrieve raw high-resolution SDO AIA, the model includes horizon computation for a smooth and accurate transition at the terminators. The model is 100% pythonic, featuring parallel execution. We present observations and numerical simulations of the ionosphere-thermosphere system bolstering the importance of the accurate EUV eclipse description. We present use 21 August 2017, and 10 June 2021 solar eclipses as examples to show the effects of realistic EUV flux and transient gradients within the penumbra, and compare it with simulations using symmetric penumbra. We integrated the EUV penumbra in the Global Ionosphere Thermosphere Model (GITM), and show that the difference between EUV and symmetric eclipse amounts to as much as plus-minus 1 TECu.

We describe mid-latitude plasma density striations (MDS) modulating the evening side of Storm Enhanced Density (SED) by magnetosphere-ionosphere coupling. The MDS are magnetically conjugate, and they consist of elongated density structures [enhancements (plumes) and depletions (troughs)] that extend from the equator to the main trough equatorward boundary. Each density perturbation is associated with a flow channel, and they develop progressively at all latitudes. We present a detailed analysis of the MDS during the 7-8 September 2017 storm, by virtue of remote and in-situ observations of the magnetosphere-ionosphere system. We find that the density plumes are a result of local plasma uplift, and poleward and westward plasma transport guided by the adjacent flow channels. While the MDS’s troughs bear some resemblance to the depletion patterns associated with equatorial plasma bubbles, it has been found to be quite distinct, both in terms of its observational manifestations and its formation mechanism. Namely, the trough is associated with enhanced flow channels peaking at the edges, with elevated electron and ion temperatures. Crucial spacecraft measurements of plasma parameters in the ionosphere and plasmasphere near the equatorial plane ($L\approx1.9$) unambiguously show conjugate nature of the MDS. In particular, the magnetospheric electric field intensifications lie just earthward of the injected $<$200~keV ions at the ion pressure gradient.

In previous work (Hairston et al., GRL doi 10.1029/2018GL077381, 2018) we showed the topside F-layer (~850 km) electron temperatures measured by two DMSP spacecraft as they flew through the Moon’s shadow during the 21 August 2017 eclipse exhibited a series of non-uniform, banded decreases rather than a broad and smooth temperature decrease. We found that making a “mask” of the shadow of the Moon eclipsing the existing active regions on the sun’s surface created a pattern on the ionosphere showing where the gradient of the EUV from the active regions was greatest. The complex pattern of these areas from the mask at the F-peak altitude at 300 km corresponded to the areas in the topside F-layer where the DMSP observed the bands of cooled electrons. We have expanded this work to examine about a dozen other eclipses including the most recent 21 June 2020 eclipse. We repeatedly observed the same banded pattern in the electron temperatures in almost all the DMSP eclipse passes, thus demonstrating this is a repeatable phenomenon. Since the DMSP series of spacecraft form a constellation of four operational satellites with the same plasma instrument package making multiple measurements of the shadow at different local times, and sometimes within 10-15 minutes of each other, we can use these observations to map the shape and evolution of these cooling band patterns as the eclipse’s shadow passes over the Earth’s ionosphere. Here we will present our first detailed analysis of the two eclipses that occurred on 20-21 May 2012 and 2 July 2019. Both these eclipses have passes through the duskside by two spacecraft within a few minutes of each other, thus allowing us to examine the evolution of the pattern. We are using these events to determine the empirical patterns seen in the electron temperature decreases during eclipses and to explore the mechanism causing the cooling of the plasma and how it is transported from the F-peak region to the topside ionosphere.