Estimating the extremes in European geomagnetic activity

Rapidly changing geomagnetic field variations constitute a natural hazard, for example in navigation and, through geomagnetically induced currents, to power grids and pipeline networks. To understand this hazard we have continuous magnetic measurements across the world for typically less than 100 years. Much of the older data is also in analogue form, or is only available digitally as hourly or daily magnetic indices or mean levels. So it may not yet be clear what the true extremes in geomagnetic variations are, particularly on time scales - seconds to minutes - that are relevant for estimating the hazard to technological systems. We therefore use a number of decades of one minute samples of magnetic data from observatories across Europe, together with the technique of 'extreme value statistics’ to explore estimated maxima in field variations in the horizontal strength and in the declination of the field. These maxima are expressed in terms of the variations that might be observed once every 100 and 200 years. We also examine the extremes in one-minute rates of change of these field components over similar time scales. The results should find application in both hazard assessment for technologies and in navigation applications. The results can also be used to more rigorously answer the often-asked question: “just how large can geomagnetic storms and field variations be?

Recent work at the World Data Centre for Geomagnetism (Edinburgh)

Observatory data holdings at the World Data Centre for Geomagnetism (Edinburgh) www.wdc.bgs.ac.uk include minute, hourly and annual mean values of the geomagnetic field from over 500 observatories since the early 19th century. We describe ongoing maintenance of this important data resource, data-checking procedures developed with global modelling in mind, and some recent additions and corrections

Geomagnetic extreme statistics for Europe

Rapidly changing geomagnetic field variations constitute a natural hazard, for example to grounded power grids and pipeline networks. To understand this hazard we have continuous magnetic measurements across the world for typically less than 100 years. Much of the older data is also in analogue form, or is only available digitally as hourly or daily magnetic indices or mean levels. So it may not yet be clear what the true extremes in geomagnetic variation are, particularly on time scales - seconds to minutes - that are relevant for estimating the hazard to technological systems. We therefore use a number of decades of one minute samples of magnetic data from observatories in Europe, together with the technique of 'extreme value statistics', to explore estimated maxima in field variations in the horizontal strength and in the declination of the field. These maxima are expressed, for example, in terms of the variations that might be observed on time scales of 100 and 200 years. We also examine the extremes in the one-minute rate of change of these field components on similar time scales. The results should find application in hazard assessment and navigation applications

A comparison of data holdings at World Data Centres for geomagnetism in Edinburgh and Kyoto

Geomagnetic data are held by a number of World Data Centres (WDC) with each Centre having different holdings and different methods of distribution. These Centres are run by institutes in Boulder, Edinburgh, Kyoto, Moscow and Mumbai. Using data from two of these WDCs we describe methods to compare temporal coverage of data, and, importantly, the data themselves. This study examines the hourly data common to Edinburgh and Kyoto and gives details of the number of observatory-years of data where disagreements are found, and quantifies the level of disagreement. We show several examples of datasets that differ between the two WDCs, and report on the nature of the differences in detail. Finally, we explore possible reasons for the differences found between the data holdings and suggest next steps towards the unification of the WDC data holdings

Quality control procedures at the World Data Centre for Geomagnetism (Edinburgh)

Geomagnetism data holdings at the World Data Centre for Geomagnetism (Edinburgh) include observatory minute, hourly and annual mean values and global magnetic survey and repeat station data. Until 2007 the observatory minute and hourly mean value holdings were maintained by the Danish Meteorological Institute. We describe the quality control procedures developed at the British Geological Survey for application to new and legacy data. A number of issues raised for the legacy observatory hourly mean values result from formatting and typographical mistakes. The clearly obvious mistakes are being corrected in the WDC data that are made available at www.wdc.bgs.ac.uk. Whilst these quality control procedures have been mostly developed with the application of global modelling in mind, they will have benefits for all users of the data. Some examples of corrections are given

Operations of the World Data Centre for Geomagnetism (Edinburgh)

The British Geological Survey has operated a World Data Centre for Geomagnetism since 1966. We hold geomagnetic time-series from around 280 observatories worldwide, for a number of time- resolutions from one-minute to annual, along with various magnetic survey, model and activity index data. The operation of this dynamic data centre contributes towards global geomagnetic field modelling efforts and provides a valuable service to the worldwide research community. We describe the operation of this data centre detailing the range of data held and our data collection, storage and distribution processes and infrastructure. We describe the quality control checks we apply to incoming data and our work interacting with other data centres for geomagnetism to share data and improve the overall consistency of data held. We also demonstrate how we are developing the metadata associated with our datasets and note the current issues around establishing metadata standards for geomagnetism

Quantifying extreme behaviour in geomagnetic activity

Understanding the extremes in geomagnetic activity is an important component in understanding just how severe conditions can become in the terrestrial space environment. Extreme activity also has consequences for technological systems. On the ground, extreme geomagnetic behavior has an impact on navigation and position accuracy and the operation of power grids and pipeline networks. We therefore use a number of decades of one-minute mean magnetic data from magnetic observatories in Europe, together with the technique of extreme value statistics, to provide a preliminary exploration of the extremes in magnetic field variations and their one-minute rates of change. These extremes are expressed in terms of the variations that might be observed every 100 and 200 years in the horizontal strength and in the declination of the field. We find that both measured and extrapolated extreme values generally increase with geomagnetic latitude (as might be expected), though there is a marked maximum in estimated extreme levels between about 53 and 62 degrees north. At typical midlatitude European observatories (55–60 degrees geomagnetic latitude), compass variations may reach approximately 3–8 degrees/minute, and horizontal field changes may reach 1000–4000 nT/minute, in one magnetic storm once every 100 years. For storm return periods of 200 years the equivalent figures are 4–11 degrees/minute and 1000–6000 nT/minute

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe