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1. Derivation of Hemispheric Ionospheric Current Functions From Ground‐Level Magnetic Fields

   https://doi.org/10.1029/2018JA026191  

   Weimer, D. R. (April 2019, Journal of Geophysical Research: Space Physics)

   Abstract The horizontal currents in the high‐latitude ionosphere are the primary driver of the magnetic field perturbations that are observed at the surface of the Earth. These currents and their ground effects are an important aspect of the magnetosphere‐ionosphere coupling process. This paper discusses the method of inversion that uses spherical harmonic potential function, in which magnetic field measurements on the ground can be used to derive maps of the “ionospheric equivalent currents,” a mathematical representation of the horizontal currents flowing on a thin shell. It is shown that the use of both internal telluric and external current sources is required when fitting the spherical harmonic series; otherwise, the ionospheric currents will be overestimated. Furthermore, the inversion needs to compensate for magnetic effects of the magnetospheric ring current; otherwise, this current is projected onto the ionosphere. The amplification of the surface horizontal magnetic field and the suppression of the vertical magnetic field are demonstrated. The equivalent currents may be useful for estimating the ionospheric conductivity values. Additionally, these currents can be compared with the results from simulation models as a means of validation. 

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2. Arctic tidal current atlas

   https://doi.org/10.1038/s41597-020-00578-z  

   Baumann, Till M.; Polyakov, Igor V.; Padman, Laurie; Danielson, Seth; Fer, Ilker; Janout, Markus; Williams, William; Pnyushkov, Andrey V. (August 2020, Scientific Data)

   Abstract Tidal and wind-driven near-inertial currents play a vital role in the changing Arctic climate and the marine ecosystems. We compiled 429 available moored current observations taken over the last two decades throughout the Arctic to assemble a pan-Arctic atlas of tidal band currents. The atlas contains different tidal current products designed for the analysis of tidal parameters from monthly to inter-annual time scales. On shorter time scales, wind-driven inertial currents cannot be analytically separated from semidiurnal tidal constituents. Thus, we include 10–30 h band-pass filtered currents, which include all semidiurnal and diurnal tidal constituents as well as wind-driven inertial currents for the analysis of high-frequency variability of ocean dynamics. This allows for a wide range of possible uses, including local case studies of baroclinic tidal currents, assessment of long-term trends in tidal band kinetic energy and Arctic-wide validation of ocean circulation models. This atlas may also be a valuable tool for resource management and industrial applications such as fisheries, navigation and offshore construction. 

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3. Variation in Oceanographic Resistance of the World's Coastlines to Invasion by Species With Planktonic Dispersal

   https://doi.org/10.1111/ele.14520  

   Byers, James E; Pringle, James M (September 2024, Ecology Letters)

   ABSTRACT For marine species with planktonic dispersal, invasion of open ocean coastlines is impaired by the physical adversity of ocean currents moving larvae downstream and offshore. The extent species are affected by physical adversity depends on interactions of the currents with larval life history traits such as planktonic duration, depth and seasonality. Ecologists have struggled to understand how these traits expose species to adverse ocean currents and affect their ability to persist when introduced to novel habitat. We use a high‐resolution global ocean model to isolate the role of ocean currents on the persistence of a larval‐producing species introduced to every open coastline of the world. We find physical adversity to invasion varies globally by several orders of magnitude. Larval duration is the most influential life history trait because increased duration prolongs species' exposure to ocean currents. Furthermore, variation of physical adversity with life history elucidates how trade‐offs between dispersal traits vary globally. 

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4. Continuing Current Seen Above and Below the Cloud: Comparing Observations From GLM and High‐Speed Video Cameras

   https://doi.org/10.1029/2024GL110099  

   Ding, Ziqin; Zhu, Yanan; Lapierre, Jeff; DiGangi, Elizabeth; Ringhausen, Jacquelyn; Lauria, Paola_B; Saba, Marcelo_M_F; Rakov, Vladimir_A; Abbasi, Rasha_U; da_Silva, Diego_R_R; et al (August 2024, Geophysical Research Letters)

   Abstract This study assesses the reliability and limitations of the Geostationary Lightning Mapper (GLM) in detecting continuing currents by comparing observations from ground‐based high‐speed cameras with GLM‐16 data. Our findings show that the GLM's one‐group detection efficiency (DE_1) is 53%, while the more stringent five‐consecutive‐group detection efficiency (DE_5) is 10%. Optical signals detected by the GLM predominantly occur during the early stages of continuing currents. Additionally, there is a notable disparity in detection efficiencies between positive and negative continuing currents, with positive continuing currents being detected more frequently. The application of the logistic regression model developed by Fairman and Bitzer (2022) further illustrates the limitations in continuing current identification. The study underscores the challenges of relying solely on satellite data to monitor and analyze continuing currents, emphasizing the need for advancements in detection technologies and methodologies to reliably detect continuing current at a large spatial scale. 

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5. On the Relationship Between Regions of Large‐Scale Field‐Aligned Currents and Regions of Plateau in Plasma Pressure Observed in the Equatorial Plane of the Earth's Magnetosphere

   https://doi.org/10.1029/2023GL105190  

   Kirpichev, I P; Antonova, E E; Stepanova, M V (September 2023, Geophysical Research Letters)

   Abstract Since the discovery of the large‐scale field‐aligned currents it is widely acknowledged that gaps exist between the Region 1 (R1) and Region 2 (R2) currents in which the current values are relatively small as compared to neighboring regions. Assuming that the field‐aligned currents are generated by plasma pressure gradients, we analyzed data collected by the THEMIS satellites between 2007 and 2011 to identify regions with very low plasma pressure gradients (pressure plateaus), which could be responsible for the appearance of these gaps. It was found that the pressure profiles with low radial gradients are typically located between 8 and 10 Radii around the Earth. Projections of pressure plateau regions onto ionospheric altitudes, for both individual events and on a statistical basis, coincide with the locations of gaps between Iijima and Potemra field‐aligned currents. The role played by identified pressure plateaus in shaping the pattern of large‐scale field‐aligned currents is discussed. 

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