Aurora in the Polar Cap: A Review

This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sun-aligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic field (IMF). We also introduce polar rain aurora which has been considered as a phenomenon on open field lines. We describe the morphology of such auroras, their development and dynamics in response to solar wind-magnetosphere coupling processes, and the models that have been developed to explain them

Hot plasma in the magnetotail lobes shows characteristics consistent with closed field lines trapped in the lobes

We examine the magnetotail using data from the Hot Ion Analyzer on Cluster 1 during 2001–2009. We develop and utilise an algorithm in order to identify times during which Cluster 1 is in the magnetotail lobe but observes plasma which is hotter than our expectations of the lobe. We analyze the prevailing Interplanetary Magnetic Field (IMF) Bz conditions for our algorithm and a reference algorithm (with no particle energy criteria) and find that the periods we select are, on average, ~2 nT more towards northward IMF. Examining the temperature in the magnetotail for our periods shows that the morphology of the average temperature is consistent with the Milan et al. (2005) model of magnetotail structure during Northward IMF, in which closed field lines are prevented from convecting to the dayside, causing them and the plasma trapped on them to protrude into the magnetotail lobes. We also find evidence that ~0.5% of our identified periods may be driven by direct entry into the magnetosphere from the solar wind

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

An investigation into the fine-scale structure of Polar Cap Aurora using ground-based and spacecraft instrumentation

This thesis will investigate the formation and structure of polar cap arcs using groundbased and spacecraft instrumentation. In particular, we present polar cap arc substructure down to unprecedented spatial and temporal scales using the Auroral Structure and Kinetics (ASK) instrument. Events are identified using images from Special Sensor Ultra-violet Spectrographic Imager (SSUSI) instruments on board Defence Meteorological Satellite Program (DMSP) F16-F19. Three studies are presented. First, an event with polar cap arcs occurring on the dawn and duskside of the northern hemisphere on 19 January 2008 was observed by SSUSI instruments on board DMSP F16 and F17. The structure on the duskside occurred over Svalbard and was analysed using a multitude of ground-based instrumentation, including ASK, and was found to be consistent with formation on closed field lines. The arc on the dawnside of the northern hemisphere was found, using in-situ particle data, to be consistent with formation on open field lines. This first study shows that polar cap arcs consistent with different formation mechanisms can occur simultaneously. The second study surveyed SSUSI and corresponding SSJ/5 data to identify and classify polar cap arc events in December 2015. Further examples of arcs occurring on both magnetic field topologies are found as well as examples that are not, at first sight, consistent with either. The occurrence frequency of polar cap arcs is also investigated and they are found to be present in the SSUSI images at least 20% of the time. Finally, two events with polar cap arcs consistent with different magnetic field topologies occurring over Svalbard are analysed using ASK data. The first occurred on 4 February 2016 and is consistent with formation on closed field lines; the second occurred on 15 December 2015 and is consistent with open field lines. The small-scale structure within these arcs is found to be quite different and consistent with their occurrence on different magnetic field toplogies. The ground-based observations are then compared to the spacecraft observations to infer more information about the two formation mechanisms

Northeast Asia Defense Transparency Index  2021–22

Military tensions are on the rise in Northeast Asia as the likes of China, North Korea, and the United States flex their combat capabilities—but this does not mean that war is imminent. This is an important insight from the latest Northeast Asia Defense Transparency Index (DTI) for the period spanning 2021 to 2022. Carried out every two years by the University of California’s Institute on Global Conflict and Cooperation, the DTI offers a detailed examination of how open or closed major regional states are in disclosing information on their defense postures, including defense budgets, publication of official annual defense reports, legislative oversight, and the nature of external military activities.The 2021–22 DTI found that there was only a marginal decline in the overall defense transparency level for Northeast Asia, with Japan showing a noteworthy improvement in its transparency performance. The concealment of defense activities is often an indicator that countries are quietly making preparations for military conflict and contributes to declining trust and confidence. The evidence from this DTI that defense transparency is relatively stable in Northeast Asia is cause for cautious optimism that the long peace that the region has enjoyed remains intact for now. Transparency though is just one indicator of the overall state of defense affairs, and the powerful underlying currents that are the main determinants of war and peace, such as threat perceptions and arms dynamics, all appear to be trending negatively

Aurora in the polar cap: a review

This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sun-aligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic field (IMF). We also introduce polar rain aurora which has been considered as a phenomenon on open field lines. We describe the morphology of such auroras, their development and dynamics in response to solar wind-magnetosphere coupling processes, and the models that have been developed to explain them.</p

Dataset for Multi-scale observations of two polar cap arcs occuring on different magnetic field topologies

This dataset supports the publication: Reidy, J. A., R. C. Fear, D. K. Whiter, B. S. Lanchester, A. J. Kavanagh, D. J. Price, J. M. Chadney, Y. Zhang, and L. J. Paxton. Multi-scale observation of two polar cap arcs occurring on different magnetic field topologies. J. Geophys. Res. 2020</span