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1. Poynting Flux Input to the Auroral Ionosphere: The Impact of Subauroral Polarization Streams and Dawnside Auroral Polarization Streams

   https://doi.org/10.1029/2024JA032605  

   Liu, Jiang; Lyons, L_R; Knipp, Delores; Zhang, Qiang; Wang, Chih‐Ping; Shen, Yangyang; Angelopoulos, V.; Ma, Yuzhang; Tian, Sheng; Artemyev, A.; et al (May 2024, Journal of Geophysical Research: Space Physics)

   Abstract The Poynting vector (Poynting flux) from Earth's magnetosphere downward toward its ionosphere carries the energy that powers the Joule heating in the ionosphere and thermosphere. The Joule heating controls fundamental ionospheric properties affecting the entire magnetosphere‐ionosphere‐thermosphere system, so it is necessary to understand when and where the Poynting flux is significant. Taking advantage of new data sets generated from DMSP (Defense Meteorological Satellite Program) observations, we investigate the Poynting flux distribution within and around the auroral zone, where most magnetosphere‐ionosphere (M‐I) dynamics and thus Joule heating occurs. We find that the Poynting flux, which is generally larger under more active conditions, is concentrated in the sunlit cusp and near the interface between Region 1 and 2 currents. The former concentration suggests voltage generators drive the cusp dynamics. The latter concentration shows asymmetries with respect to the interface between the Region 1 and 2 currents. We show that these reflect the controlling impact of subauroral polarization streams and dawnside auroral polarization streams on the Poynting flux. 

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2. Simultaneous Development of Multiple Auroral Substorms: Double Auroral Bulge Formation

   https://doi.org/10.1029/2020JA028883  

   Ohtani, S.; Gjerloev, J_W; McWilliams, K_A; Ruohoniemi, J_M; Frey, H_U (May 2021, Journal of Geophysical Research: Space Physics)

   Abstract The expansion phase of auroral substorms is characterized by the formation of an auroral bulge, and it is generally considered that a single bulge forms following each substorm onset. However, we find that occasionally two auroral intensifications takes place close in time but apart in space leading to the formation of double auroral bulges, which later merge into one large bulge. We report three such events. In those events the westward auroral electrojet intensified in each auroral bulge, and geosynchronous magnetic field dipolarized in the same sector. It appears that two substorms took place simultaneously, and each substorm was accompanied by the formation of its own substorm current wedge system. This finding strongly suggests that the initiation of auroral substorms is a local process, and there is no global reference frame for their development. For example, ideas such as (i) the auroralbreakup takes place in the vicinity of the Harang reversal and (ii) the westward traveling surge maps to the interface between the plasma sheet and low‐latitude boundary layer, do not necessarily hold for every substorm. Even if those ideas may be suggestive of causal magnetospheric processes, the reference structures themselves are probably not essential. It is also found that despite the formation of two distinct auroral bulges, the overall magnetosphere‐ionosphere current system is represented by one globally coherent system, and we suggest that its structure is determined by the relative intensities and locations of the two substorm current wedges that correspond to the individual auroral bulges. 

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3. A Contrastive Learning Approach to Auroral Identification and Classification

   https://doi.org/10.1109/icmla52953.2021.00128  

   Johnson, Jeremiah W.; Hari, Swathi; Hampton, Donald; Connor, Hyunju K.; Keesee, Amy (December 2021, 20th IEEE International Conference on Machine Learning and Applications (ICMLA))
4. Auroral Heating of Plasma Patches Due to High‐Latitude Reconnection

   https://doi.org/10.1029/2021JA029657  

   Díaz Peña, Joaquín; Semeter, Joshua; Nishimura, Yukitoshi; Varney, Roger; Reimer, Ashton; Hairston, Marc; Zettergren, Matthew; Hirsch, Michael; Verkhoglyadova, Olga; Hosokawa, Keisuke; et al (December 2021, Journal of Geophysical Research: Space Physics)
5. Mid-latitude neutral wind responses to sub-auroral polarization streams

   https://doi.org/10.5194/angeo-40-571-2022  

   Billett, Daniel D.; McWilliams, Kathryn A.; Kerr, Robert B.; Makela, Jonathan J.; Chartier, Alex T.; Ruohoniemi, J. Michael; Kapali, Sudha; Migliozzi, Mike A.; Riccobono, Juanita (January 2022, Annales Geophysicae)

   Abstract. We investigate the response of the mid-latitude thermospheric neutral winds to a sub-auroral polarization stream (SAPS) event. Using red line (F region) airglow data from two Fabry–Pérot interferometers (FPIs), and F-region ionospheric flow velocities from four Super Dual Auroral Radar Network (SuperDARN) radars, the drivers behind changes seen in the neutral winds are explored within the context of the larger SAPS structure. Different, although strong, neutral wind responses to the SAPS are seen at the two FPI sites, even though they are relatively close geographically. We attribute the wind differences to the varying balance of pressure gradient, ion drag, and Coriolis forces, which ultimately depend on proximity to the SAPS. At the FPI site equatorward of the SAPS, pressure gradient and Coriolis forces drive the winds equatorward and then westward. At the FPI site co-located with the SAPS, the ion drag is strong and results in the winds surging westward before turning eastward when becoming influenced by dawnside sunward plasma convection drifts. 

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