Hydrogen has been inferred to occur in enhanced concentrations within permanently shadowed regions and, hence, the coldest areas of the lunar poles. The Lunar Crater Observation and Sensing Satellite ...(LCROSS) mission was designed to detect hydrogen-bearing volatiles directly. Neutron flux measurements of the Moon's south polar region from the Lunar Exploration Neutron Detector (LEND) on the Lunar Reconnaissance Orbiter (LRO) spacecraft were used to select the optimal impact site for LCROSS. LEND data show several regions where the epithermal neutron flux from the surface is suppressed, which is indicative of enhanced hydrogen content. These regions are not spatially coincident with permanently shadowed regions of the Moon. The LCROSS impact site inside the Cabeus crater demonstrates the highest hydrogen concentration in the lunar south polar region, corresponding to an estimated content of 0.5 to 4.0% water ice by weight, depending on the thickness of any overlying dry regolith layer. The distribution of hydrogen across the region is consistent with buried water ice from cometary impacts, hydrogen implantation from the solar wind, and/or other as yet unknown sources.
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Discharge current pulse profiles have been recorded with a subnanosecond time resolution for a corona discharge from a negative-polarity needle functioning in the Trichel pulse regime. The optical ...characteristics of plasma glow have been measured with a high spatial resolution. This corona discharge has been numerically simulated within a two-dimensional theoretical model taking into account plasmochemical kinetics. It has been shown that Trichel pulses are initiated in atmospheric-pressure air when positive ions are concentrated near the needle to the critical concentration for an avalanche-to-streamer transition, in particular, at a dc voltage across a gap (in several or several tens of seconds). It has been established that the nanosecond pulse front is determined by the time of avalanche multiplication of electrons in the region of a locally enhanced field. It has been shown that a short duration of a Trichel pulse is due to the fast displacement of the electric field from the dense-plasma region and to the escape of free electrons from this region with the subsequent disappearance through recombination and attachment. It has been established that the density of the ion–ion air plasma in the local region in front of the needle in an interval between Trichel pulses remains at a level of 10
11
cm
–3
, which ensures the subsequent generation of new Trichel pulses.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Soft γ-ray repeaters exhibit bursting emission in hard X-rays and soft γ-rays. During the active phase, they emit random short (milliseconds to several seconds long), hard-X-ray bursts, with peak ...luminosities
of 10
to 10
erg per second. Occasionally, a giant flare with an energy of around 10
to 10
erg is emitted
. These phenomena are thought to arise from neutron stars with extremely high magnetic fields (10
to 10
gauss), called magnetars
. A portion of the second-long initial pulse of a giant flare in some respects mimics short γ-ray bursts
, which have recently been identified as resulting from the merger of two neutron stars accompanied by gravitational-wave emission
. Two γ-ray bursts, GRB 051103 and GRB 070201, have been associated with giant flares
. Here we report observations of the γ-ray burst GRB 200415A, which we localized to a 20-square-arcmin region of the starburst galaxy NGC 253, located about 3.5 million parsecs away. The burst had a sharp, millisecond-scale hard spectrum in the initial pulse, which was followed by steady fading and softening over 0.2 seconds. The energy released (roughly 1.3 × 10
erg) is similar to that of the superflare
from the Galactic soft γ-ray repeater SGR 1806-20 (roughly 2.3 × 10
erg). We argue that GRB 200415A is a giant flare from a magnetar in NGC 253.
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Results of a theoretical description of collisionless kinetics of radial expansion of two-component (electron–ion) plasma in the one-dimensional cylindrical formulation of the problem are presented. ...The electric-field mechanism of supersonic expansion of the plasma flame due to the motion of the electron–ion ensemble and self-consistent electric field in the diode with the potential difference applied to it is demonstrated. The spatiotemporal evolution of the ion energy distribution function, electric potential, and rate of expansion of the emission boundary of the plasma flame is shown. The calculated rates of flame expansion at the copper cathode (~1.5 × 10
6
cm/s) well agree with the experimental data.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The transient process of establishing the electron current in a vacuum diode is theoretically investigated, in which the kinetic energies of electrons can exceed the amplitude value of the applied ...voltage (multiplied by the elementary charge). It is shown theoretically that when a high voltage pulse with a short leading edge is applied to a planar vacuum diode, the first peak of relaxation current oscillations is provided by an electron beam of “anomalously” high energies. It is noted that the degree of “abnormality” of electron beam energies significantly depends on the density of the emission current from the cathode, and in some hypothetical cases, it can exceed the applied voltage several times.
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The article analyzes the processes of project management in the implementation of social and environmental programs in the Arctic zone of the Russian Federation. Current regulatory and legal acts ...aimed at ensuring the development of the Arctic zone are considered. The problems of rational environmental management, development of territories with minimal negative impact on the state of the environment and taking into account the environmental situation in the region is identified. State programs for support and assistance to people living and working in the regions of the Arctic zone of the Russian Federation, aimed at economic support, development of a personnel reserve and health preservation, and environmental projects, are analyzed and presented. The priority importance of social and environmental projects to develop infrastructure, improve the quality of life of the population and preserve the primary ecosystem is noted. The use of methods for calculating environmental safety indices and urban environment quality indices of the Ministry of Construction of the Russian Federation when ranking the subjects of the Arctic zone made it possible to identify the most problematic areas in ensuring the quality of life, and, accordingly, priority areas for the development and implementation of strategic projects. The importance of strategic programs and projects to reduce the level of pollutants, to increase the population’s supply of high-quality drinking water in cities and to improve the quality of the urban environment is emphasized to improve the quality of life of residents of the cities of the Arctic region.
Abstract
The paper presents a 2D multi-fluid non-stationary model of a negative corona discharge in atmospheric-pressure air in the needle-to-plane diode. Discharges were simulated in gaps up to 1 cm ...with an applied voltage in the range of 8-100 kV. The simulation results demonstrate two stages of the discharge evolution: a pulsed-periodic stage called the Trichel pulses mode and a stationary glow discharge mode. The spatio-temporal distributions of the discharge plasma and electric field are shown in detail. Physical mechanism of Trichel pulses formation and transition to the stationary discharge are also revealed. The duration of the Trichel pulse mode gradually decreases with increasing of the applied voltage.
•LEND/LRO instrument neutron counting data sets have been analyzed to create high resolution maps of epithermal neutron flux at polar regions of the Moon.•The conversion from epithermal neutron flux ...to the H/H2O abundances is presented based on the simple subsurface models.•The polar lunar maps (poleward 70S/70N) of homogeneous hydrogen distribution are derived and discussed.
We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top ∼1m layer of lunar regolith. Polar maps of the Moon's inferred hydrogen abundance are presented and discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Unsteady equations of flat and axisymmetric boundary layers are considered. For the unsteady axisymmetric boundary layer equation, the problem of group classification is solved. It is shown that the ...kernel of symmetry operators can be extended by no more than four-dimensional Lie algebra. The kernel of symmetry operators of the unsteady flat boundary layer equation is found and it is shown that it can be extended by no more than a five-dimensional Lie algebra. The non-existence of the unsteady analogue of the Stepanov–Mangler transformation is proved.
ExoMars is a two-launch mission undertaken by Roscosmos and European Space Agency. Trace Gas Orbiter, a satellite part of the 2016 launch carries the Fine Resolution Neutron Detector instrument as ...part of its payload. The instrument aims at mapping hydrogen content in the upper meter of Martian soil with spatial resolution between 60 and 200 km diameter spot. This resolution is achieved by a collimation module that limits the field of view of the instruments detectors. A dosimetry module that surveys the radiation environment in cruise to Mars and on orbit around it is another part of the instrument.
This paper describes the mission and the instrument, its measurement principles and technical characteristics. We perform an initial assessment of our sensitivity and time required to achieve the mission goal. The Martian atmosphere is a parameter that needs to be considered in data analysis of a collimated neutron instrument. This factor is described in a section of this paper. Finally, the first data accumulated during cruise to Mars is presented.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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