618 research outputs found
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 windβbased βdayside merging potentialβ Ξ¦d = LeffVBt sin4(ΞΈ/2), whereas to characterize the nightside source we integrated across the tail the dawn-dusk electric field in the plasma sheet (to obtain the βcross-tail potentialβ Ξ¦n). 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 Ξ¦fit = KdΞ¦d + KnΞ¦n + Ξ¦0) 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, 1583–1591, 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.Π Π΄Π°Π½Π½ΠΎΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°Π΅ΡΡΡ Π²Π»ΠΈΡΠ½ΠΈΠ΅ Π½Π°Π»ΠΈΡΠΈΡ shift-ΡΠ΅Π°ΠΊΡΠΎΡΠ° ΠΈ ΡΠ·Π»Π° ΡΠ΄Π°Π»Π΅Π½ΠΈΡ Π‘Π2 (CCS) ΠΈΠ· ΡΠΈΠ½ΡΠ΅Π·-Π³Π°Π·Π° (ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡ pre-combustion) Π½Π° ΡΠ΅ΡΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΠΠ ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠΉ ΠΏΠ°ΡΠΎΠ³Π°Π·ΠΎΠ²ΠΎΠΉ ΡΡΡΠ°Π½ΠΎΠ²ΠΊΠΈ Ρ Π²Π½ΡΡΡΠΈΡΠΈΠΊΠ»ΠΎΠ²ΠΎΠΉ Π³Π°Π·ΠΈΡΠΈΠΊΠ°ΡΠΈΠ΅ΠΉ ΡΠ²ΡΡΠ΄ΠΎΠ³ΠΎ ΡΠΎΠΏΠ»ΠΈΠ²Π° (ΠΠΠ£-ΠΠ¦Π). ΠΡΠΎΠ²Π΅Π΄Π΅Π½ Π°Π½Π°Π»ΠΈΠ· Π»ΠΈΡΠ΅ΡΠ°ΡΡΡΠ½ΡΡ
ΠΈΡΡΠΎΡΠ½ΠΈΠΊΠΎΠ² ΠΏΠΎ Π²Π»ΠΈΡΠ½ΠΈΡ CCS Π½Π° ΡΠ΅ΡΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΠΠ ΡΡΡΡ
ΠΊΠΈΡΠ»ΠΎΡΠΎΠ΄Π½ΡΡ
ΠΠΠ£-ΠΠ¦Π. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½ΠΎ ΡΠ°ΡΡΠ΅ΡΠ½ΠΎΠ΅ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΡΡΠ΅ΠΏΠ΅Π½ΠΈ ΠΈΠ½ΡΠ΅Π³ΡΠ°ΡΠΈΠΈ CCS Π² ΡΡ
Π΅ΠΌΡ Π΄Π΅ΠΌΠΎΠ½ΡΡΡΠ°ΡΠΈΠΎΠ½Π½ΠΎΠΉ ΠΠΠ£-ΠΠ¦Π Π½Π° ΡΠΎΡΡΠ°Π² ΡΠΆΠΈΠ³Π°Π΅ΠΌΠΎΠ³ΠΎ Π³Π°Π·ΠΎΠ²ΠΎΠ³ΠΎ ΡΠΎΠΏΠ»ΠΈΠ²Π°. ΠΡΠΈΠ²ΠΎΠ΄ΠΈΡΡΡ ΠΏΡΠΈΠ½ΡΠΈΠΏ ΡΠ°Π±ΠΎΡΡ shift-ΡΠ΅Π°ΠΊΡΠΎΡΠ°. Π Π°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°ΡΡΡΡ ΡΠ°Π·Π»ΠΈΡΠ½ΡΠ΅ ΡΠΈΠΏΡ ΠΊΠ°ΡΠ°Π»ΠΈΠ·Π°ΡΠΎΡΠΎΠ², ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅ΠΌΡΡ
Π² shift-ΡΠ΅Π°ΠΊΡΠΎΡΠ΅. ΠΡΠΎΠ°Π½Π°Π»ΠΈΠ·ΠΈΡΠΎΠ²Π°Π½ΠΎ Π²Π»ΠΈΡΠ½ΠΈΠ΅ CCS Π½Π° ΡΠΊΠΎΠ½ΠΎΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΈ ΡΠΊΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΠΈ ΠΠΠ£-ΠΠ¦Π. ΠΡΠΎΠ²Π΅Π΄Π΅Π½ Π°Π½Π°Π»ΠΈΠ· ΡΡ
Π΅ΠΌ ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠΉ Π²ΠΎΠ·Π΄ΡΡΠ½ΠΎΠΉ ΠΠΠ£-ΠΠ¦Π Ρ ΡΠ·Π»ΠΎΠΌ CCS ΠΈ Π±Π΅Π· Π½Π΅Π³ΠΎ
ΠΠ± ΠΈΡΡΠΎΡΠΈΠΈ ΠΎΡΠΊΡΡΡΠΈΡ ΠΈ ΠΏΡΠΈΡΠΎΠ΄Π΅ Π°Π»ΠΌΠ°Π·ΠΎΠ² Π² Π²ΡΠ»ΠΊΠ°Π½ΠΈΡΠ΅ΡΠΊΠΈΡ ΠΏΠΎΡΠΎΠ΄Π°Ρ ΠΠ°ΠΌΡΠ°ΡΠΊΠΈ
The history of the discovery of diamonds in the products of Kamchatka volcanic eruptions is briefly described, and the results of comprehensive studies of Tolbachin diamonds including crystallomorphology, faceted sculptures, xenomineral greases and films on the surface, nanomicroswitches, impurity elements, spectroscopic properties, isotopic composition of carbon and nitrogen are summarized. The conclusion is drawn about the natural origin of the Tolbachin diamonds formed directly in the volcanic ash-gas cloud by crystallization from gases stimulated by atmospheric electric discharges.ΠΡΠ°ΡΠΊΠΎ ΠΎΠΏΠΈΡΠ°Π½Π° ΠΈΡΡΠΎΡΠΈΡ ΠΎΡΠΊΡΡΡΠΈΡ Π°Π»ΠΌΠ°Π·ΠΎΠ² Π² ΠΏΡΠΎΠ΄ΡΠΊΡΠ°Ρ
ΠΈΠ·Π²Π΅ΡΠΆΠ΅Π½ΠΈΠΉ Π²ΡΠ»ΠΊΠ°Π½ΠΎΠ² ΠΠ°ΠΌΡΠ°ΡΠΊΠΈ ΠΈ ΠΎΠ±ΠΎΠ±ΡΠ΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΡΠΎΠ»Π±Π°ΡΠΈΠ½ΡΠΊΠΈΡ
Π°Π»ΠΌΠ°Π·ΠΎΠ² β ΠΊΡΠΈΡΡΠ°Π»Π»ΠΎΠΌΠΎΡΡΠΎΠ»ΠΎΠ³ΠΈΠΈ, Π³ΡΠ°Π½Π½ΠΎΠΉ ΡΠΊΡΠ»ΡΠΏΡΡΡΡ, ΠΊΡΠ΅Π½ΠΎΠΌΠΈΠ½Π΅ΡΠ°Π»ΡΠ½ΡΡ
ΠΏΡΠΈΠΌΠ°Π·ΠΎΠΊ ΠΈ ΠΏΠ»Π΅Π½ΠΎΠΊ Π½Π° ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ, Π½Π°Π½ΠΎΠΌΠΈΠΊΡΠΎΠ²ΠΊΠ»ΡΡΠ΅Π½ΠΈΠΉ, ΡΠ»Π΅ΠΌΠ΅Π½ΡΠΎΠ²-ΠΏΡΠΈΠΌΠ΅ΡΠ΅ΠΉ, ΡΠΏΠ΅ΠΊΡΡΠΎΡΠΊΠΎΠΏΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ²ΠΎΠΉΡΡΠ², ΠΈΠ·ΠΎΡΠΎΠΏΠ½ΠΎΠ³ΠΎ ΡΠΎΡΡΠ°Π²Π° ΡΠ³Π»Π΅ΡΠΎΠ΄Π° ΠΈ Π°Π·ΠΎΡΠ°. Π‘Π΄Π΅Π»Π°Π½ Π²ΡΠ²ΠΎΠ΄ ΠΎ ΠΏΡΠΈΡΠΎΠ΄Π½ΠΎΠΌ ΠΏΡΠΎΠΈΡΡ
ΠΎΠΆΠ΄Π΅Π½ΠΈΠΈ ΡΠΎΠ»Π±Π°ΡΠΈΠ½ΡΠΊΠΈΡ
Π°Π»ΠΌΠ°Π·ΠΎΠ², ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π²ΡΠΈΡ
ΡΡ Π½Π΅ΠΏΠΎΡΡΠ΅Π΄ΡΡΠ²Π΅Π½Π½ΠΎ Π² ΡΡΠ΅Π΄Π΅ Π²ΡΠ»ΠΊΠ°Π½ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΏΠ΅ΠΏΠ»ΠΎΠ³Π°Π·ΠΎΠ²ΠΎΠ³ΠΎ ΠΎΠ±Π»Π°ΠΊΠ° ΠΏΡΡΠ΅ΠΌ ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΈΠ· Π³Π°Π·ΠΎΠ², ΡΡΠΈΠΌΡΠ»ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ Π°ΡΠΌΠΎΡΡΠ΅ΡΠ½ΡΠΌΠΈ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ ΡΠ°Π·ΡΡΠ΄Π°ΠΌΠΈ
Josephson Vortex States in Intermediate Fields
Motivated by recent resistance data in high 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,
, 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
. 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
Flow Induced Organization and Memory of a Vortex Lattice
We report on experiments probing the evolution of a vortex state in response
to a driving current in 2H-NbSe crystals. By following the vortex motion
with fast transport measurements we find that the current enables the system to
reorganize and access new configurations. During this process the system
exhibits a long-term memory: if the current is turned off the vortices freeze
in place remembering their prior motion. When the current is restored the
motion resumes where it stopped. The experiments provide evidence for a
dynamically driven structural change of the vortex lattice and a corresponding
dynamic phase diagram that contains a previously unknown regime where the
critical current can be either or by applying an
appropriate driving current.Comment: 5 pages, 4figure
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