| 51. |
- Eriksson, S., et al.
(författare)
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Magnetic island formation between large-scale flow vortices at an undulating postnoon magnetopause for northward interplanetary magnetic field
- 2009
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114:2, s. A00C17-
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Tidskriftsartikel (refereegranskat)abstract
- Time History of Events and Macroscale Interactions during Substorms multispacecraft observations are presented for a similar to 2-h-long postnoon magnetopause event on 8 June 2007 that for the first time indicate that the trailing (sunward) edges of Kelvin-Helmholtz (KH) waves are commonly related to small-scale < 0.56 R-E magnetic islands or flux transfer events (FTE) during the growth phase of these surface waves. The FTEs typically show a characteristic bipolar B-N structure with enhanced total pressure at their center. Most of the small-scale FTEs are not related to any major plasma acceleration. TH-A observations of one small FTE at a transition from the low-latitude boundary layer (LLBL) into a magnetosheath plasma depletion layer were reconstructed using separate techniques that together confirm the presence of a magnetic island within the LLBL adjacent to the magnetopause. The island was associated with a small plasma vortex and both features appeared between two large-scale (similar to 1 R-E long and 2000 km wide) plasma vortices. We propose that the observed magnetic islands may have been generated from a time-varying reconnection process in a low ion plasma beta (beta(i) < 0.2) and low 8.3 degrees field shear environment at the sunward edge of the growing KH waves where the local magnetopause current sheet may be compressed by the converging flow of the large-scale plasma vortices as suggested by numerical simulations of the KH instability.
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| 52. |
- Hamrin, Maria, et al.
(författare)
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Observations of concentrated generator regions in the nightside magnetosphere by Cluster/FAST conjunctions
- 2006
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 24, s. 637-49
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Tidskriftsartikel (refereegranskat)abstract
- Here and in the companion paper, Marghitu et al. (2006), we investigate plausible auroral generator regions in the nightside auroral magnetosphere. In this article we use magnetically conjugate data from the Cluster and the FAST satellites during a 3.5-h long event from 19-20 September 2001. Cluster is in the Southern Hemisphere close to apogee, where it probes the plasma sheet and lobe at an altitude of about 18 RE. FAST is below the acceleration region at approximately 0.6 RE. Searching for clear signatures of negative power densities, E(.)J < O, in the Cluster data we can identify three concentrated generator regions (CGRs) during our event. From the magnetically conjugate FAST data we see that the observed generator regions in the Cluster data correlate with auroral precipitation. The downward Poynting flux observed by Cluster, as well as the scale size of the CGRs, are consistent with the electron energy flux and the size of the inverted-V regions observed by FAST. To our knowledge, these are the first in-situ observations of the crossing of an auroral generator region. The main contribution to E(.)J < O comes from the GSE E(y)J(y). The electric field E-y is weakly negative during most of our entire event and we conclude that the CGRs occur when the duskward current J(y) grows large and positive. We find that our observations are consistent with a local southward expansion of the plasma sheet and/or rather complicated, 3-D wavy structures propagating over the Cluster satellites. We find that the plasma is working against the magnetic field, and that kinetic energy is being converted into electromagnetic energy. Some of the energy is transported away as Poynting flux.
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| 53. |
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| 54. |
- Marghitu, O., et al.
(författare)
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Auroral arc and oval electrodynamics in the Harang region
- 2009
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- Auroral arcs are typically described in terms of an upward field-aligned current (FAC) sheet above the arc, connected by ionospheric Pedersen current to a downward FAC sheet near the arc. On the basis of data measured by the FAST spacecraft, conjugate with ground optical observations, we present first a wide and stable winter evening arc, where this standard model does not apply. The arc is observed in the Harang region during the growth phase of a modest substorm, poleward of the convection reversal (CR) boundary. Although the magnetic field data suggest the typical configuration, the two FAC sheets appear to be decoupled near the satellite footprint: the upward FAC is fed by the westward electrojet (WEJ), while the downward FAC feeds the eastward electrojet (EEJ). The examination of the arc by the newly developed ALADYN technique confirms this peculiar current topology. For comparison, we apply ALADYN also to a second evening arc, located within the Harang region equatorward from the CR. The arc is confirmed to have the standard configuration, consistent with a former study, but substantial FAC-EJ coupling is inferred in the auroral oval both poleward and equatorward of the arc. A key element for the topology of the current closure is the westward component of the electric field, which influences the relative location of the CR with respect to the large-scale FAC reversal (FR) boundary. As proved by tests on synthetic data, a westward component of the electric field pushes the CR toward the FR, preventing thus the standard FAC closure, while the conductance and FAC pattern shape the CR profile. Since a westward electric field is often measured in the Harang region, the FAC-EJ coupling is expected to be an essential ingredient there. This has important implications for the current closure in the equatorial magnetosphere and for the auroral current circuit in the WEJ region, closely related to the substorm process.
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| 55. |
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| 56. |
- Spitzer, Ernest, et al.
(författare)
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Critical Appraisal of Contemporary Clinical Endpoint Definitions in Coronary Intervention Trials A Guidance Document
- 2019
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Ingår i: JACC. - : Elsevier. - 1936-8798 .- 1876-7605. ; 12:9, s. 805-819
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Forskningsöversikt (refereegranskat)abstract
- The Academic Research Consortium (ARC) and the Standardized Data Collection for Cardiovascular Trials Initiative have recently published updated clinical and angiographic endpoint definitions for percutaneous coronary intervention trials. The aim of this document is to provide practical guidance to facilitate and harmonize the implementation of those definitions in randomized trials or registries, as well as to foster consistency among independent adjudication committees. The authors compared the ARC-2 and Standardized Data Collection for Cardiovascular Trials Initiative definitions to identify areas of consistency, complex scenarios, and definitions in need of further standardization. Furthermore, the authors compared the fourth universal definition of myocardial infarction with the ARC-2 definition of myocardial infarction. The Society for Cardiovascular Angiography and Interventions definition of periprocedural myocardial infarction was also compared with the ARC-2 definition and the fourth universal definition of myocardial infarction. An in-depth assessment was done for each individual clinical endpoint to guide clinical investigators on reporting and classifying clinical adverse events. Finally, the authors propose standard streamlined data capture templates for reporting and adjudicating death, myocardial infarction, stroke, revascularization, stent or scaffold thrombosis, and bleeding. (c) 2019 by the American College of Cardiology Foundation.
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| 57. |
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| 58. |
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