Preseismic ULF electromagnetic effect from observation at Kamchatka

International audienceSome results of ULF magnetic field observation at Karimshino site (Kamchatka, Russia) since June 2000 to September 2001 are presented here. Using case study we have found an effect of suppression of ULF intensity about 2?6 days before rather strong and nearby seismic shocks (magnitude M = 4.0 ? 6.2). It is revealed for nighttime and horizontal component of ULF field (G) in the frequency range 0.01 ? 0.1 Hz. Then we prove the reliability of the effect by computed correlation between G (or 1/G) and specially calculated seismic indexes Ks for the whole period of observation. Basing on the simple criteria we conclude that reliability of seismo-associated ULF suppression effect is comparable with well-known effect of connection between ULF variation and Kp index of global magnetic activity. It seems the reason of suppression is located at the atmosphere or ionosphere but not in the ground medium

A commutator description of the solvable radical of a finite group

We are looking for the smallest integer k>1 providing the following characterization of the solvable radical R(G) of any finite group G: R(G) coincides with the collection of all g such that for any k elements a_1,a_2,...,a_k the subgroup generated by the elements g, a_iga_i^{-1}, i=1,...,k, is solvable. We consider a similar problem of finding the smallest integer l>1 with the property that R(G) coincides with the collection of all g such that for any l elements b_1,b_2,...,b_l the subgroup generated by the commutators [g,b_i], i=1,...,l, is solvable. Conjecturally, k=l=3. We prove that both k and l are at most 7. In particular, this means that a finite group G is solvable if and only if in each conjugacy class of G every 8 elements generate a solvable subgroup

Corrigendum to "Time-varying magnetotail magnetic flux calculation: a test of the method" published in Ann. Geophys., 27, 1583–1591, 2009

No abstract available

Electric fields in plasmas under pulsed currents

Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for 3D spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously.Comment: 13 pages, 13 figures, submitted to PR

Contribution of magnetotail reconnection to the cross-polar cap electric potential drop

Since the work of Dungey (1961), the global circulation pattern with two (dayside and nightside) reconnection regions has become a classic concept. However, the contributions of dayside and nightside sources to the cross-polar cap potential (PCP) are not fully understood, particularly, the relative role and specifics of the nightside source are poorly investigated both in quantitative and qualitative terms. To fill this gap, we address the contributions of dayside and nightside sources to the PCP by conducting global MHD simulations with both idealized solar wind input and an observed event input. The dayside source was parameterized by solar wind–based “dayside merging potential” Φd = LeffVBt sin4(θ/2), whereas to characterize the nightside source we integrated across the tail the dawn-dusk electric field in the plasma sheet (to obtain the “cross-tail potential” Φn). For the idealized run we performed simulations using four MHD codes available at the Community Coordinated Modeling Center to show that contribution of the nightside source is a code-independent feature (although there are many differences in the outputs provided by different codes). Particularly, we show that adding a nightside source to the linear fit function for the ionospheric potential (i.e., using the fit function Φfit = KdΦd + KnΦn + Φ0) considerably improves the fitting results both in the idealized events as well as in the simulation of an observed event. According to these simulations the nightside source contribution to the PCP has a fast response time (<5 min) and a modest efficiency (potential transmission factor from tail to the ionosphere is small, Kn < 0.2), which is closely linked to the primarily inductive character of strong electric field generated in the plasma sheet. The latter time intervals are marked by strongly enhanced nightside (lobe) reconnection and can be associated with substorm expansion phases. This association is further strengthened by the simulated patterns of precipitation, the R1-type field-aligned substorm current wedge currents and Hall electrojet currents, which are consistent with the known substorm signatures

Every Newborn INDEPTH (EN-INDEPTH) Study - Additional Materials

The Every Newborn- International Network for the Demographic Evaluation of Populations and their Health (EN-INDEPTH) study was a cross-sectional, multi-site study conducted between July 2017 and August 2018, including a survey of 69,176 women aged 15-49 years in five Health and Demographic Surveillance Sites (HDSS) within the INDEPTH Network: Bandim in Guinea-Bissau, Dabat in Ethiopia, IgangaMayuge in Uganda, Matlab in Bangladesh and Kintampo in Ghana. The primary objective of the study was to compare two methods of retrospective recording of pregnancy outcomes in surveys: Full Birth History with additional questions on pregnancy losses (FBH+), and Full Pregnancy History (FPH). A secondary objective was to identify barriers and enablers to the reporting of pregnancy and adverse pregnancy outcomes during the survey and HDSS data collection, and particularly if these differ for the two survey questionnaire methods (FBH+ and FPH). The study also evaluated the use of existing/modified survey questions to capture the fertility intentions and selected pregnancy outcomes (Termination of Pregnancy, miscarriage, birthweight, gestational age), and birth and death certification

Highly Conductive Fe-Doped (La,Sr)(Ga,Mg)O3−δ Solid-State Membranes for Electrochemical Application

Membranes based on complex solid oxides with oxygen-ionic conductivity are widely used in high-temperature electrochemical devices such as fuel cells, electrolyzers, sensors, gas purifiers, etc. The performance of these devices depends on the oxygen-ionic conductivity value of the membrane. Highly conductive complex oxides with the overall composition of (La,Sr)(Ga,Mg)O3 have regained the attention of researchers in recent years due to the progress in the development of electrochemical devices with symmetrical electrodes. In this research, we studied how the introduction of iron cations into the gallium sublattice in (La,Sr)(Ga,Mg)O3 affects the fundamental properties of the oxides and the electrochemical performance of cells based on (La,Sr)(Ga,Fe,Mg)O3. It was found that the introduction of iron leads to an increase in the electrical conductivity and thermal expansion in an oxidizing atmosphere, while no such behavior was observed in a wet hydrogen atmosphere. The introduction of iron into a (La,Sr)(Ga,Mg)O3 electrolyte leads to an increase in the electrochemical activity of Sr2Fe1.5Mo0.5O6−δ electrodes in contact with the electrolyte. Fuel cell studies have shown that, in the case of a 550 µm-thick Fe-doped (La,Sr)(Ga,Mg)O3 supporting electrolyte (Fe content 10 mol.%) and symmetrical Sr2Fe1.5Mo0.5O6−δ electrodes, the cell exhibits a power density of more than 600 mW/cm2 at 800 °C. © 2023 by the authors

Mass Transfer Mechanism in Real Crystals by Pulsed Laser Irradiation

The dynamic processes in the surface layers of metals subjected activity of a pulsing laser irradiation, which destroyed not the crystalline structure in details surveyed. The procedure of calculation of a dislocation density generated in bulk of metal during the relaxation processes and at repeated pulse laser action is presented. The results of evaluations coincide with high accuracy with transmission electron microscopy dates. The dislocation-interstitial mechanism of laser-stimulated mass-transfer in real crystals is presented on the basis of the ideas of the interaction of structure defects in dynamically deforming medium. The good compliance of theoretical and experimental results approves a defining role of the presented mechanism of mass transfer at pulse laser action on metals. The possible implementation this dislocation-interstitial mechanism of mass transfer in metals to other cases of pulsing influences is justifiedComment: 10 pages, 2 figures, Late