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

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

No abstract available

Near-seismic effects in ULF fields and seismo-acoustic emission: statistics and explanation

International audiencePreseismic intensification of fracturing has been investigated from occurrence analysis of seismo-acoustic pulses (SA foreshocks) and ULF magnetic pulses (ULF foreshocks) observed in Karimshino station in addition to seismic foreshocks. Such analysis is produced for about 40 rather strong and nearby isolated earthquakes during 2 years of recording. It is found that occurrence rate of SA foreshocks increases in the interval (-12, 0 h) before main shock with 3-times exceeding of background level in the interval (-6, -3 h), and occurrence probability of SA foreshocks (pA~75%) is higher than probability of seismic foreshocks (ps~30%) in the same time interval.ULF foreshocks are masked by regular ULF activity at local morning and daytime, nevertheless we have discovered an essential ULF intensity increase in the interval (-3, +1 h) at the frequency range 0.05-0.3 Hz. Estimated occurrence probability of ULF foreshocks is about 40%. After theoretical consideration we conclude: 1) Taking into account the number rate of SA foreshocks, their amplitude and frequency range, they emit due to opening of fractures with size of L=70-200 m (M=1-2); 2) The electro-kinetic effect is the most promising mechanism of ULF foreshocks, but it is efficient only if two special conditions are fulfilled: a) origin of fractures near fluid-saturated places or liquid reservoirs (aquifers); b) appearance of open porosity or initiation of percolation instability; 3) Both SA and ULF magnetic field pulses are related to near-distant fractures (r<20-30 km); 4) Taking into account number rate and activation period of seismic, SA and ULF foreshocks, it is rather probable that opening of fractures and rupture of fluid reservoirs occur in the large preparation area with horizontal size about 100-200km

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

Analysis of advanced IGCC economic indicators

In this paper, the influence presence of a shift reactor and a CO2 removal unit (CCS) from syngas (pre-combustion technology) on the thermal efficiency of a combined-cycle plant with in-cycle gasification of solid fuel (IGCC) is considered. The literature sources on the effect of CCS on the thermal efficiency of three oxygen IGCC are analyzed. The calculated influence of the degree of integration of CCS in the demonstration IGCC scheme on the composition of the combusted gas fuel is presented. The principle of shift-reactor operation is given. Various types of catalysts used in the shift reactor are considered. The influence of CCS on the economic and environmental indicators of IGCC is analyzed. The analysis of air IGCC schemes with CCS node and without it is carried out.В данной работе рассматривается влияние наличия shift-реактора и узла удаления СО2 (CCS) из синтез-газа (технология pre-combustion) на термический КПД перспективной парогазовой установки с внутрицикловой газификацией твёрдого топлива (ПГУ-ВЦГ). Проведен анализ литературных источников по влиянию CCS на термический КПД трёх кислородных ПГУ-ВЦГ. Представлено расчетное влияние степени интеграции CCS в схему демонстрационной ПГУ-ВЦГ на состав сжигаемого газового топлива. Приводится принцип работы shift-реактора. Рассматриваются различные типы катализаторов, используемых в shift-реакторе. Проанализировано влияние CCS на экономические и экологические показатели ПГУ-ВЦГ. Проведен анализ схем перспективной воздушной ПГУ-ВЦГ с узлом CCS и без него

Josephson Vortex States in Intermediate Fields

Motivated by recent resistance data in high $T_c$ superconductors in fields {\it parallel} to the CuO layers, we address two issues on the Josephson-vortex phase diagram, the appearances of structural transitions on the observed first order transition (FOT) curve in intermediate fields and of a lower critical point of the FOT line. It is found that some rotated pinned solids are more stable than the ordinary rhombic pinned solids with vacant interlayer spacings and that, due to the vertical portion in higher fields of the FOT line, the FOT tends to be destroyed by creating a lower critical point.Comment: 12 pages, 3 figures. To appear in J.Phys.Soc.Jpn. 71, No.2 (February, 2002

Rapid dissipation of magnetic fields due to Hall current

We propose a mechanism for the fast dissipation of magnetic fields which is effective in a stratified medium where ion motions can be neglected. In such a medium, the field is frozen into the electrons and Hall currents prevail. Although Hall currents conserve magnetic energy, in the presence of density gradients, they are able to create current sheets which can be the sites for efficient dissipation of magnetic fields. We recover the frequency, $\omega_{MH}$, for Hall oscillations modified by the presence of density gradients. We show that these oscillations can lead to the exchange of energy between different components of the field. We calculate the time evolution and show that magnetic fields can dissipate on a timescale of order $1/\omega_{MH}$. This mechanism can play an important role for magnetic dissipation in systems with very steep density gradients where the ions are static such as those found in the solid crust of neutron stars.Comment: 9 pages, changed fig.

Disturbances in groundwater chemical parameters related to seismic and volcanic activity in Kamchatka (Russia)

International audienceStarting from 1992 geochemical data are being collected with a mean sampling frequency of three days in the form of the pH value and of the most common ions and gases in the groundwater in one deep well located in Petropavlovsk, the capital city of Kamchatka (Russia). On 1 January 1996 a strong eruption started from the Karymsky volcano, that is located about 100km far from the well, in the north-northeastern direction. At the same time, a large earthquake (M=6.9) occurred in the Karymsky area. On 5 December 1997 a very large earthquake (M=7.7) occurred offshore, at a distance of 350km from the well and towards the same direction. The analysis of the geochemical data shows clear variations in the raw temporal trends on both cases. For the first event, a clear premonitory phase appeared; for the second one, some pre-seismic variations could be revealed but permanent modifications of the chemistry of the water subsequent to the earthquake are very clear. In both cases the feature of the geochemical variations is consistent with an afflux of new water in the aquifer connected with the well and with an escape of the Carbon dioxide gas from the ground in different directions. A schematic model able to justify such a phenomenology and the connections of the geochemical variations with the previous tectonic activities is proposed