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We present a new technique for the upcoming tri‐static incoherent scatter radar system EISCAT 3D (E3D) to perform a volumetric reconstruction of the 3D ionospheric electric current density vector field, focusing on the feasibility of the E3D system. The input to our volumetric reconstruction technique are estimates of the 3D current density perpendicular to the main magnetic field, j⊥, and its covariance, to be obtained from E3D observations based on two main assumptions: (a) Ions fully magnetized above the E region, set to 200 km here. (b) Electrons fully magnetized above the base of our domain, set to 90 km. In this way, j⊥ estimates are obtained without assumptions about the neutral wind field, allowing it to be subsequently determined. The volumetric reconstruction of the full 3D current density is implemented as vertically coupled horizontal layers represented by Spherical Elementary Current Systems with a built‐in current continuity constraint. We demonstrate that our technique is able to retrieve the three dimensional nature of the currents in our idealized setup, taken from a simulation of an active auroral ionosphere using the Geospace Environment Model of Ion‐Neutral Interactions (GEMINI). The vertical current is typically less constrained than the horizontal, but we outline strategies for improvement by utilizing additional data sources in the inversion. The ability to reconstruct the neutral wind field perpendicular to the magnetic field in the E region is demonstrated to mostly be within ±50 m/s in a limited region above the radar system in our setup. Plain Language Summary: We introduce a novel method for the upcoming EISCAT 3D (E3D) radar system to reconstruct the 3D electric current density vector in Earth's ionosphere. Here we present the new technique and assess its feasibility for the E3D system. The input to the 3D reconstruction technique relies on estimates of the current density perpendicular to the Earth's magnetic field, obtained from the E3D observations. We include estimates of uncertainties originating from the observations of the 3D ion velocity vectors and electron density in our reconstruction. Comparisons with simulations of an active auroral ionosphere exemplify that our technique provides reasonably accurate estimates of current density, especially in the 90–150 km altitude range. Our results demonstrate success in retrieving the horizontal part of the electric current system in the E region, while the vertical part has more uncertainty. Our method offers insight into how electric currents flow in a specific region of the Earth's atmosphere. The results can be further improved with additional data sources; this flexibility is a significant advantage of our approach. Overall, our study facilitates the advanced knowledge of Earth's upper atmosphere using innovative radar observations in companion with advanced analysis techniques. Key Points: A technique for volumetric reconstruction of 3D electric current density from tri‐static incoherent scatter radar observations is presentedConsidering the anticipated noise levels, the radar system is likely to produce good current density estimates in a limited regionThe reconstruction technique is particularly well suited for inclusion of additional data sources that improve overall performance [ABSTRACT FROM AUTHOR]

Calculating the magnetic flux transfer across the open‐closed boundary (OCB) per unit time and distance—the reconnection electric field—is an important means of remotely monitoring magnetospheric dynamics. Ground‐based measurements of plasma convection velocities together with velocities of the OCB are commonly used to infer reconnection rates. However, this approach is limited by spatial coverage and often lacks robust uncertainty quantification. In this paper, we assimilate Super Dual Auroral Radar Network convection measurements, ground magnetometer data, and estimates of the conductance derived from the Imager for Magnetopause‐to‐Aurora Global Exploration satellite imagers, using the Local mapping of polar ionospheric electrodynamics (Lompe) framework over a region in North America. We present a new method to assess various contributions to uncertainties in the derived reconnection electric fields, including a novel approach to estimate uncertainties in conductance from global auroral imaging. Our method is demonstrated on a substorm event with an associated pseudobreakup during a period of favorable observational coverage. In this case study, the uncertainties in the reconnection electric field are ∼5–10 mV/m at the peak of substorm expansion, roughly 15% of the peak reconnection electric field. We find that the main contributor to the reconnection electric field estimates after substorm onset is the OCB motion, whereas during the pseudobreakup the main contributor is ionospheric plasma convection. Plain Language Summary: The solar wind is a stream of particles and magnetic field flowing away from the Sun. Under certain orientations of the solar wind magnetic field, magnetic reconnection can occur between the magnetic fields of the solar wind and Earth. Magnetic reconnection is the process by which oppositely directed magnetic field lines "break," then merge into a new configuration. Magnetic reconnection is the primary process responsible for coupling the solar wind energy to the Earth's magnetic field, and is ultimately the principal driver of space weather. In the Earth's magnetosphere, reconnection is associated with topological changes at both dayside and nightside, where stored magnetic energy is released through a global reconfiguration of the magnetosphere which is referred to as magnetospheric substorms. We can remotely monitor this reconnection from the ground by studying the transfer of magnetic flux across the boundary between open and closed magnetic field lines. In this study, we combined data from ground‐based radars, ground magnetometers, and space‐based auroral imaging to monitor the reconnection rate across the entire nightside auroral oval for a full substorm event. We additionally derived uncertainties in this reconnection rate stemming from uncertainties in the ionospheric velocities, the ionospheric conductances, and the open‐closed boundary motion. Key Points: We estimate Hall and Pedersen conductance uncertainties using global auroral satellite images from Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) for an isolated substormWe calculate uncertainties in ionospheric reconnection electric fields related to conductance, open‐closed boundary (OCB) motion, and convectionWe find that the main contributor to the reconnection electric field estimates after onset is the OCB motion [ABSTRACT FROM AUTHOR]

The aurora often appears as an approximately oval shape surrounding the magnetic poles, and is a visible manifestation of the intricate coupling between the Earth's upper atmosphere and the near-Earth space environment. While the average size of the auroral oval increases with geomagnetic activity, the instantaneous shape and size of the aurora is highly dynamic. The identification of auroral boundaries holds significant value in space physics, as it serves to define and differentiate regions within the magnetosphere connected to the aurora by magnetic field lines. In this work, we demonstrate a new method to estimate the spatiotemporal variations of the poleward and equatorward boundaries in global UV images. We apply our method, which is robust against outliers and occasional bad data, to 2.5 years of UV imagery from the Imager for Magnetopause-to-Aurora Global Exploration satellite. The resulting data set is compared to recently published boundaries based on the same images (Chisham et al., 2022, https://doi.org/10.1029/2022JA030622), and shown to give consistent results on average. Our data set reveals a root mean square boundary normal velocity of 149 m/s for the poleward boundary and 96 m/s for the equatorward boundary and the velocities are shown to be stronger on the nightside than on the dayside. Interestingly, our findings demonstrate an absence of correlation between the amount of open magnetic flux and the amount of flux enclosed within the auroral oval. [ABSTRACT FROM AUTHOR]

Energetic Electron Precipitation (EEP) from the Earth's plasma sheet and the radiation belts is an important feature of atmospheric dynamics through their destruction of ozone in the lower thermosphere and mesosphere. Therefore, understanding the magnitude of the atmospheric impact of the Sun‐Earth interaction requires a comprehensive understanding of the intensity and location of EEP. This study improves the accuracy of a previous pressure‐corrected Dst model that predicts the equatorward extent of >43, >114, and >292 keV EEP using the measurements from the Medium Energy Proton Electron Detector detector of six National Oceanic and Atmospheric Administration/Polar Orbiting Environmental Satellites and EUMETSAT/METOP satellites. The improvement is achieved through multiple linear regression of pressure‐corrected Dst and pressure‐corrected Ring Current (RC) indices. The RC index mitigates the baseline variation of the Dst index that created an inherent solar cycle bias in the previous model. The new model is then extended to the Southern Hemisphere (SH) after removing the South Atlantic Anomaly longitudes from the data. More than 80% of the residuals lie within ±1.8° Corrected Geomagnetic Latitude (CGMLat) in the Northern Hemisphere and within ±1.98° CGMLat in the SH. Plain Language Summary: This study aims to construct a model that predicts the geographic extent of Energetic Electron Precipitation (EEP) from the Earth's radiation belts using measurements from the Medium Energy Proton Electron Detector detector of six National Oceanic and Atmospheric Administration/Polar Orbiting Environmental Satellites and EUMETSAT/METOP satellites. The study enhances the accuracy of the previous pressure‐corrected Dst model. This improvement is implemented using multiple linear regression of pressure‐corrected Dst and pressure‐corrected Ring Current (RC) indices. Additionally, the study extends the model to the Southern Hemisphere after removing the South Atlantic Anomaly longitudes from the data. The result resolves the solar cycle bias that existed in the previous study. Key Points: An updated model of the equatorward extent of >43 keV electron precipitation has been improved by successfully removing the solar cycle biasIncluding both the Dst* and the Ring Current index reduces the error estimate to ±1.8° Corrected Geomagnetic Latitude (CGMLat) over a full solar cycle (2004–2014)The model is extended to the Southern Hemisphere with an error estimate of ±1.98° CGMLat [ABSTRACT FROM AUTHOR]

Lobe reconnection is usually thought to play an important role in geospace dynamics only when the Interplanetary Magnetic Field (IMF) is mainly northward. This is because the most common and unambiguous signature of lobe reconnection is the strong sunward convection in the polar cap ionosphere observed during these conditions. During more typical conditions, when the IMF is mainly oriented in a dawn‐dusk direction, plasma flows initiated by dayside and lobe reconnection both map to high‐latitude ionospheric locations in close proximity to each other on the dayside. This makes the distinction of the source of the observed dayside polar cap convection ambiguous, as the flow magnitude and direction are similar from the two topologically different source regions. We here overcome this challenge by normalizing the ionospheric convection observed by the Super Dual Aurora Radar Network (SuperDARN) to the polar cap boundary, inferred from simultaneous observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). This new method enable us to separate and quantify the relative contribution of both lobe reconnection and dayside/nightside (Dungey cycle) reconnection during periods of dominating IMF By. Our main findings are twofold. First, the lobe reconnection rate can typically account for 20% of the Dungey cycle flux transport during local summer when IMF By is dominating and IMF Bz ≥ 0. Second, the dayside convection relative to the open/closed boundary is vastly different in local summer versus local winter, as defined by the dipole tilt angle. Plain Language Summary: Reconnection of magnetic field lines at high latitudes, tailward of the magnetic poles, is most often thought to play a big role in near‐Earth space dynamics only when the magnetic field carried by the solar wind, the Interplanetary Magnetic Field or IMF, has a large northward component. This is because such conditions lead to the distinct strong sunward movement of plasma at polar latitudes in the ionosphere. During more typical conditions (when the IMF is dawn/dusk directed), identifying and quantifying the effect of such high‐latitude reconnection becomes much more challenging. This paper presents a new technique that enables this separation even when the dawn‐dusk component of the IMF is dominating, by normalizing the convection to the boundary between open and closed magnetic field lines. We make two main findings. First, the summer and winter dayside plasma flows near the boundary between open and closed magnetic field lines are vastly different. Second, plasma circulation at polar latitudes (interpreted as lobe reconnection rate) can on average account for ∼20% $\sim 20\%$ of the total plasma transport during local summer when IMF is mostly directed in the dawn‐dusk direction and IMF Bz is northward. Key Points: We demonstrate a novel technique to quantify the polar cap plasma circulation statisticallyDuring local summer and By dominated Interplanetary Magnetic Field (IMF), lobe reconnection is estimated to amount to ∼20% of the dayside reconnection rateIn the local summer hemisphere, dayside polar cap convection is more vortical compared to the local winter hemisphere during IMF By periods [ABSTRACT FROM AUTHOR]

North‐south asymmetries arise in the magnetosphere‐ionosphere system when a significant east‐west (By) component is present in the interplanetary magnetic field (IMF). During such conditions, a By component with the same sign as the IMF By component is induced in the magnetosphere, and the locations of conjugate magnetic footpoints are displaced between the two hemispheres. It has been suggested that these asymmetries are introduced into the closed magnetosphere by tail reconnection. However, recent studies instead suggest that asymmetric lobe pressure induces the asymmetries, which are then reduced during periods of enhanced tail reconnection. To address this, we use the Lyon‐Fedder‐Mobarry (LFM) model and initiate a loading‐unloading cycle in multiple runs by changing the IMF. Asymmetries are induced during the loading phase and reduced during the unloading phase. The model results thus suggest that asymmetries arise during periods with low tail reconnection and are reduced during periods with enhanced tail reconnection. Plain Language Summary: The aurora is a bright and beautiful manifestation of Earth's connection to space, and can light up the night sky in the high latitude regions in both hemispheres. However, auroral features do not always occur at the expected magnetic location in the two hemispheres, but are often displaced in the longitudinal direction between the Northern and Southern Hemisphere. The displacement is related to the orientation of the magnetic field in the solar wind, but the exact mechanisms responsible for causing and removing this displacement are debated. Previous simulations of the plasma environment around the Earth suggest that when this magnetic field intensifies in the dawn‐dusk direction, magnetic pressure builds up asymmetrically in each hemisphere, causing the displacement. Here we present new simulation results showing that the longitudinal displacement is reduced when magnetic reconnection happens in the Earth's magnetotail. Key Points: The evolution of the asymmetric state of the magnetosphere is examined by using the Lyon‐Fedder‐Mobarry model with non‐zero interplanetary magnetic field ByThe simulation shows a clear reduction of north‐south asymmetries associated with enhanced tail reconnectionThe modeling results are consistent with the evolution seen in interhemispheric observations of aurora [ABSTRACT FROM AUTHOR]

Substorm activity is heavily influenced by the Interplanetary Magnetic Field (IMF) Bz component and magnetospheric substorms occur most frequently when Bz is strongly negative. The substorm occurrence rate is also affected by the magnitude of the By component, but it is usually presumed that this contribution is independent of the sign of By. Using five independent substorm onset lists, we show that substorm activity does depend on the sign of By near the solstices. Specifically, we show that substorms occur more frequently when By and the dipole tilt angle Ψ have different signs as opposed to when they have the same sign. These results confirm that the magnetosphere exhibits an explicit dependence on the polarity of By for nonzero Ψ, as other recent studies have suggested, and imply variation in the dayside reconnection rate and/or the magnetotail response. On the other hand, we find no clear relationship between substorm intensity and By regardless of Ψ. Last, for the onset list based on identifying negative bays at auroral latitudes, we observe an overall trend of more frequent onsets for positive By, regardless of season. However, substorm frequency in the other four substorm lists does not exhibit an overall preference for positive By. We show that this phenomenon is very likely a consequence of the particular substorm identification method (i.e., identification of negative bays), which is affected by local ionospheric conditions that depend on By and Ψ. [ABSTRACT FROM AUTHOR]

ZnO nanorods synthesised using an aqueous pH 11 solution are shown to exhibit surface-sensitive morphology post-annealing in oxygen, air, and nitrogen as shown by scanning electron microscopy and transmission electron microscopy analysis. Raman analysis confirms the nanorods were nitrogen-doped and that nitrogen incorporation takes place during the synthesis procedure in the form of N-Hx. A strong green photoluminescence is observed post-annealing for all samples, the intensity of which is dependent on the atmosphere of anneal. This luminescence is linked to zinc vacancies as recent reports have indicated that these defects are energetically favoured with the annealing conditions used herein. ZnO-nanorod/CuSCN diodes are fabricated to examine the effect of material properties on photodetector device performance. The devices exhibit a photocurrent at zero bias, creating a self-powered photodetector. A photocurrent response of 30 μA (at 6 mW cm-2 irradiance) is measured, with a rise time of ∼25 ns, and sensitivity to both UV and visible light (475-525 nm). [ABSTRACT FROM AUTHOR]