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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 ∼1 m layer of lunar regolith. Polar maps of the Moon's inferred hydrogen abundance are presented and discussed.

Lunar neutron flux data measured by the Lunar Exploration Neutron Detector (LEND) on board NASA's Lunar Reconnaissance Orbiter (LRO) were analyzed for the period 2009-2014.We have re-evaluated the instrument's collimation capability and re-estimated the neutron counting rate measured in the Field of View (FOV) of the LEND collimated detectors, and found it to be 1.070.1counts per second. We derived the spectral density of the neutron flux for various lunar regions using our comprehensive numerical model of orbital measurements. This model takes into account the location of the LEND instrument onboard LRO to calculate the surface leakage neutron flux and its propagation to the instrument detectors. Based on this we have determined the lunar neutron flux at the surface to be approx. 2 neutrons/ [sq cm/ sec] in the epithermal energy range, 0.4e V to 1keV. We have also found variations of the lunar neutron leakage flux with amplitude as large as a factor of two, by using multi-year observations to explore variations in the Galactic Cosmic Ray (GCR) flux during the 23rd-24th solar cycles.

The Lunar Exploration Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter (LRO) detects a widespread suppression of the epithermal neutron leakage flux that is coincident with the pole-facing slopes (PFS) of the Moon’s southern hemisphere. Suppression of the epithermal neutron flux is consistent with an interpretation of enhanced concentrations of hydrogen-bearing volatiles within the upper meter of the regolith. Localized flux suppression in PFS suggests that the reduced solar irradiation and lowered temperature on PFS constrains volatility to a greater extent than in surrounding regions. Epithermal neutron flux mapped with LEND’s Collimated Sensor for Epithermal Neutrons (CSETN) was analyzed as a function of slope geomorphology derived from the Lunar Orbiting Laser Altimeter (LOLA) and the results compared to co-registered maps of diurnally averaged temperature from the Diviner Lunar Radiometer Experiment and an averaged illumination map derived from LOLA. The suppression in the average south polar epithermal neutron flux on equator-facing slopes (EFS) and PFS (85–90°S) is 3.3 ± 0.04% and 4.3 ± 0.05% respectively (one-sigma-uncertainties), relative to the average count-rate in the latitude band 45–90°S. The discrepancy of 1.0 ± 0.06% between EFS and PFS neutron flux corresponds to an average of ∼23 parts-per-million-by-weight (ppmw) more hydrogen on PFS than on EFS. Results show that the detection of hydrogen concentrations on PFS is dependent on their spatial scale. Epithermal flux suppression on large scale PFS was found to be enhanced to 5.2 ± 0.13%, a discrepancy of ∼45 ppmw hydrogen relative to equivalent EFS. Enhanced poleward hydration of PFS begins between 50°S and 60°S latitude. Polar regolith temperature contrasts do not explain the suppression of epithermal neutrons on pole-facing slopes. The Supplemental on-line materials include supporting results derived from the uncollimated Lunar Prospector Neutron Spectrometer and the LEND Sensor for Epithermal Neutrons.

Orbital measurements of neutrons by the Lunar Exploring Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter are being used to quantify the spatial distribution of near surface hydrogen (H). Inferred H concentration maps have low signal-to-noise (SN) and image restoration (IR) techniques are being studied to enhance results. A single-blind, two-phase study is described in which four teams of researchers independently developed image restoration techniques optimized for LEND data. Synthetic lunar epithermal neutron emission maps were derived from LEND simulations. These data were used as ground truth to determine the relative quantitative performance of the IR methods vs. a default denoising (smoothing) technique. We review and used factors influencing orbital remote sensing of neutrons emitted from the lunar surface to develop a database of synthetic ''true'' maps for performance evaluation. A prior independent training phase was implemented for each technique to assure methods were optimized before the blind trial. Method performance was determined using several regional root-mean-square error metrics specific to epithermal signals of interest. Results indicate unbiased IR methods realize only small signal gains in most of the tested metrics. This suggests other physically based modeling assumptions are required to produce appreciable signal gains in similar low SN IR applications.

Watering the Moon About a year ago, a spent upper stage of an Atlas rocket was deliberately crashed into a crater at the south pole of the Moon, ejecting a plume of debris, dust, and vapor. The goal of this event, the Lunar Crater Observation and Sensing Satellite (LCROSS) experiment, was to search for water and other volatiles in the soil of one of the coldest places on the Moon: the permanently shadowed region within the Cabeus crater. Using ultraviolet, visible, and near-infrared spectroscopy data from accompanying craft, Colaprete et al. (p. 463 ; see the news story by Kerr ; see the cover) found evidence for the presence of water and other volatiles within the ejecta cloud. Schultz et al. (p. 468 ) monitored the different stages of the impact and the resulting plume. Gladstone et al. (p. 472 ), using an ultraviolet spectrograph onboard the Lunar Reconnaissance Orbiter (LRO), detected H 2 , CO, Ca, Hg, and Mg in the impact plume, and Hayne et al. (p. 477 ) measured the thermal signature of the impact and discovered that it had heated a 30 to 200 square-meter region from ∼40 kelvin to at least 950 kelvin. Paige et al. (p. 479) mapped cryogenic zones predictive of volatile entrapment, and Mitrofanov et al. (p. 483 ) used LRO instruments to confirm that surface temperatures in the south polar region persist even in sunlight. In all, about 155 kilograms of water vapor was emitted during the impact; meanwhile, the LRO continues to orbit the Moon, sending back a stream of data to help us understand the evolution of its complex surface structures.

The onboard time-of-flight mass reflectron MANAGA-F is described which is aimed at measuring the elemental and isotopic composition of the secondary ion fluxes generated under the influence of solar wind. It is shown that by using this apparatus, the composition of the surface regolith layer averaged over a considerable area can be determined while approaching Phobos. After the landing of the spacecraft on the surface of Phobos, the measurements will be aimed at examining the local characteristics of the regolith and a new mechanism for water synthesis in the process of ion collisions. The apparatus allows for the mass of the secondary molecular ions to be detected and determined, including organic ones which arise during the bombardment of the regolith by ions of different origins. The main scientific problems to be solved using the given apparatus are considered in the paper. The working principle of the apparatus together with its analytical and technical characteristics and design particularities are presented. Information concerning the range of its applications for solving a number of challenging tasks of contemporary science is given. The MANAGA-F apparatus is shown to be the first realization of an original new-generation onboard device that has been invented, developed, and produced at the Space Research Institute of the Russian Academy of Sciences (SRI RAS).

The peculiarities of the airborne LAZMA instrument applied for the measurement of the isotopic and elemental composition of Phobos’ regolith by the method of laser time-of-flight mass spectrometry are discussed. These measurements may confirm the assumptions that the material of Phobos is an initial substance with a composition close to carbonaceous chondrites, from which the Earth was formed. The results of the measurements may also confirm the original mechanism of the formation of the anomalous absorption of Phobos’ regolith suggested in this study. The obtained results regarding the elemental composition of the regolith may contain information about the conditions of the formation of Phobos, as well as provide information about it age. The scientific tasks of individual experiments and ways for their realization are considered in the paper. A detailed description of the airborne instrument and the principle of its operation is presented. The analytical and technical characteristics of the instrument and the peculiarities of constructive decisions are given. Data on the most important functional assemblies of the instrument, the development and transmission of scientific information to the Earth, are considered. The mass spectra presented in the paper were obtained by airborne instruments during the course of their laboratory test and the selection of the operating regime. It is demonstrated that the LAZMA instrument is the first version of the original next-generation airborne instrument constructed at the Space Research Institute and patented in Russia.

The design of the Lunar Exploration Neutron Detector (LEND) experiment is presented, which was optimized to address several of the primary measurement requirements of NASA’s Lunar Reconnaissance Orbiter (LRO): high spatial resolution hydrogen mapping of the Moon’s upper-most surface, identification of putative deposits of appreciable near-surface water ice in the Moon’s polar cold traps, and characterization of the human-relevant space radiation environment in lunar orbit. A comprehensive program of LEND instrument physical calibrations is discussed and the baseline scenario of LEND observations from the primary LRO lunar orbit is presented. LEND data products will be useful for determining the next stages of the emerging global lunar exploration program, and they will facilitate the study of the physics of hydrogen implantation and diffusion in the regolith, test the presence of water ice deposits in lunar cold polar traps, and investigate the role of neutrons within the radiation environment of the shallow lunar surface.

The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.

In subterranean rodents, which dig down the passages with frontal teeth, adaptation to the underground mode of life presumes forming of mechanisms that provide protection against inhaling dust particles of different size when digging. One of such mechanisms can be specific pattern of air flow organization in the nasal cavity. To test this assumption, comparative study of geometry and aerodynamics of nasal passages has been conducted with regard to typical representative of subterranean rodents, the mole vole, and a representative of ground rodents, the house mouse. Numerical modeling of air flows and deposition of micro- and nanoparticle aerosols indicates that sedimentation of model particles over the whole surface of nasal cavity is higher in mole vole than in house mouse. On the contrary, particles deposition on the surface of olfactory epithelium turns out to be substantially less in the burrowing rodent as compared to the ground one. Adaptive significance of the latter observation has been substantiated by experimental study on the uptake ofnanoparticles of hydrated manganese oxide MnO x (H2O)x and Mn ions from nasal cavity into brain. It has been shown with use of magnetic resonance tomography method that there is no difference between studied species with respect to intake of particles or ions by olfactory bulb when they are introduced intranasally. Meanwhile, when inhaling nanoparticle aerosol of MnCl2, deposition of Mn in mouse's olfactory bulbs surpasses markedly that in vole's bulbs. Thereby, the morphology of nasal passages as a factor determining the aerodynamics of upper respiratory tract ensures for burrowing rodents more efficient protection of both lungs and brain against inhaled aerosols than for ground ones.

As a result of cyclotron interaction with Alfven waves propagating from the sun, pitch angle diffusion of resonant particles takes place and a shell-like distribution function of resonant ions is formed at each distance from the sun. Stability of the solar wind ion shell-like distribution function with respect to excitation of waves at larger distances is addressed. It is shown in linear approximation, that in the case when the phase velocity of Alfven waves decreases with distance, ions with shell distribution excite outward propagating Alfven waves with smaller phase velocities when they advance to larger distances. The nonlinear dynamics of the wave spectrum as well as the evolution of the ion distribution function are studied. The characteristic spectrum at the high-frequency edge of the magnetohydrodynamic fluctuations is explained.

A numerical simulation and analytical theory of the radial electric field dynamics in low collisional tokamak plasmas are presented. An initial value code “ELECTRIC” has been developed to solve the ion drift kinetic equation with a full collisional operator in the Hirshman–Sigmar–Clarke form together with the Maxwell equations. Different scenarios of relaxation of the radial electric field toward the steady-state in response to sudden and adiabatic changes of the equilibrium temperature gradient are presented. It is shown, that while the relaxation is usually accompanied by the geodesic acoustic oscillations, during the adiabatic change these oscillations are suppressed and only the magnetic pumping remains. Both the collisional damping and the Landau resonance interaction are shown to be important relaxation mechanisms. Scalings of the relaxation rates versus basic plasma parameters are presented.

Plasma density and plasma wave measurements aboard the "Vega-2" spacecraft discovered two plasma density enhancements in the inner coma of comet Halley that are accompanied by bursts of plasma waves in the lower-hybrid frequency range. These events are explained by the critical ionization velocity (CIV) effects of Alfven. The persistent bursty plasma wave activity and the intermittent plasma density growth toward the cometary nucleus indicate that the CIV effect contributes to the ionization of the cometary gas.

One of the most striking features discovered during the encounter of space probe ICE and comet Giacobini-Zinner was the presence of intensive MHD turbulence even at large distances from the comet. In this paper it is shown that the mass loading of the solar wind with cometary ions can cause such a phenomenon.

It is shown that slopes of p(R) = Ω(R) ± κ(R)/m curves at Lindblad resonances determine the widths of resonance regions. The ability of galactic disks to respond to torques exerted at ILRs by perturbers (bar, density wave, galaxy-satellite, etc.) is determined by the widths of inner Lindblad resonances (ILRs). Widths of ILRs vary along the Hubble sequence of normal and barred galaxies. Galaxies having the bulge to disk ratio of masses and radii similar to the Milky Way could have wide ILRs if they are formed at the region of 2-4 kpc from their centers. A wide range of possible perturbers with pattern speeds 4≤ Ωp ≤ 26 km s≤1 kpc−1 could excite an ILR at this region of the Milky Way. Probably, the ILR of Milky Way’s grand design is located in the same region. The hole in the galactic H2 disk is also located in this region. The mechanism responsible for the origin of this hole could be similar to that opening gaps in planetary rings.

The data from the collimated sensors of the LEND instrument are shown to be of exceptionally high quality. Counting uncertainties are about 0.3% relative and are shown to be the only significant source of random error, thus conclusions based on small differences in count rates are valid. By comparison with the topography of Shoemaker crater, the spatial resolution of the instrument is shown to be consistent with the design value of 5 km for the radius of the circle over which half the counts from the lunar surface would be determined. The observed epithermal-neutron suppression factor due to the hydrogen deposit in Shoemaker crater of 0.25 plus or minus 0.04 cps is consistent with the collimated field-of-view rate of 1.7 cps estimated by Mitrofanov et al. (2010a). The statistical significance of the neutron suppressed regions (NSRs) relative to the larger surrounding polar region is demonstrated, and it is shown that they are not closely related to the permanently shadowed regions. There is a significant increase in H content in the polar regions independent of the H content of the NSRs. The non-NSR H content increases directly with latitude, and the rate of increase is virtually identical at both poles. There is little or no increase with latitude outside the polar region. Various mechanisms to explain this steep increase in the non-NSR polar H with latitude are investigated, and it is suggested that thermal volatilization is responsible for the increase because it is minimized at the low surface temperatures close to the poles.

[1] The Lunar Exploration Neutron Detector (LEND) aboard the Lunar Reconnaissance Orbiter (LRO) has been mapping the neutron flux from the Moon since July 2009. LEND has four different types of neutron detectors which allow a comprehensive study of lunar neutron emission: a pair of omnidirectional sensors for thermal and epithermal neutrons, a pair of Doppler filter sensors for thermal neutrons, four collimated sensors of epithermal neutrons, and a sensor of high-energy neutrons. This paper describes the data reduction procedures to convert the raw data into the higher-level PDS products containing neutron-counting rate maps of the Moon.

We use measurements from the Lunar Exploration Neutron Detector (LEND) collimated sensors during more than one year of the mapping phase of NASA's Lunar Reconnaissance Orbiter (LRO) mission to make estimates of the epithermal neutron flux within known large Permanently Shadowed Regions (PSRs). These are compared with the local neutron background measured outside PSRs in sunlit regions. Individual and collective analyses of PSR properties have been performed. Only three large PSRs, Shoemaker and Cabeus in the south and Rozhdestvensky U in the north, have been found to manifest significant neutron suppression. All other PSRs have much smaller suppression, only a few percent, if at all. Some even display an excess of neutron emission in comparison to the sunlit vicinity around them. Testing PSRs collectively, we have not found any average suppression for them. Only the group of 18 large PSRs, with area >200 square kilometers, show a marginal effect of small average suppression, approx. 2%, with low statistical confidence. An approx. 2% suppression corresponds to approx. 125 ppm of hydrogen taking into account the global neutron suppression near the lunar poles and assuming a homogeneous H distribution in depth in the regolith. This means that all PSRs, except those in Shoemaker, Cabeus and Rozhdestvensky U craters, do not contain any significant amount of hydrogen in comparison with sunlit areas around them at the same latitude.

Both the acceleration of cosmic rays (CR) in supernova remnant shocks and their subsequent propagation through the random magnetic field of the Galaxy are deemed to result in an almost isotropic CR spectrum. Yet the MILAGRO TeV observatory and the IceCube discovered sharp (∼ 10°) arrival anisotropies of CR nuclei. We suggest a mechanism for producing such a CR beam which operates en route to the observer. The key assumption is that CRs are scattered by a strongly anisotropic Alfven wave spectrum formed by the turbulent cascade across the local field direction. The strongest pitch-angle scattering occurs for particles moving almost precisely along the field line. Partly because this direction is also the direction of minimum of the large scale CR angular distribution, the enhanced scattering results in a weak but narrow particle excess. The width, the fractional excess and the maximum momentum of the beam are calculated from a systematic transport theory depending on a single scale l which can be associated with the longest Alfven wave, efficiently scattering the beam. The best match to all the three characteristics of the beam is achieved at l ∼ 1pc. The distance to a possible source of the beam is estimated to be within a few 100pc. Possible approaches to determination of the scale l from the characteristics of the source are discussed. The beam related large scale anisotropic CR component is found to be energy independent which is also consistent with the observations. The beam splitting mechanism to explain the combined Milagro and IceCube observations is suggested. © 2012 American Institute of Physics.

The latest neutron spectrometer measurements with the Lunar Exploration Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter (LRO) are presented. It covers more than 1 year of mapping phase starting on 15 September 2009. In our analyses we have created global maps showing regional variations in the flux of thermal (energy range 0.5 MeV), and compared these fluxes to variances in soil elemental composition, and with previous results obtained by the Lunar Prospector Neutron Spectrometer (LPNS). We also processed data from LEND collimated detectors and derived a value for the collimated signal of epithermal neutrons based on the comparative analysis with the LEND omnidirectional detectors. Finally, we have compared our final (after the data reduction) global epithermal neutron map with LPNS data.

The modulational instability and collapse of waves in the vicinity of the lower‐hybrid resonance including both magnetosonic and lower‐hybrid waves are investigated by analytical and numerical methods. The mechanism leading to the modulational instability is the nonlinear coupling of lower‐hybrid waves with the much lower‐frequency quasineutral density perturbations via the ponderomotive force. The result is a filamentation of the high‐frequency field producing elongated, cigar‐shaped nonlinear wave packets aligned along the magnetic field with the plasma expelled outside (cavities). The analytical self‐similar solutions describing cavity collapse are obtained and compared with the results of numerical simulation for both two‐ and three‐dimensional cavity geometries. It is shown that in three‐dimensional solutions the transverse, with respect to the magnetic field, contraction remains prevailing. The possibility of ion acceleration as the result of the lower‐hybrid collapse is discussed and detailed comparison is made with the observations of the phenomena in the auroral ionosphere.

A nonlinear dynamics of the mirror modes near the instability threshold is revisited. It is shown that the major saturation is provided by modification of the velocity distribution function in the vicinity of small parallel ion velocities. The final relaxation scenario is based on almost resonant particle interaction with mirror modes. The saturated plasma state can be considered as a magnetic counterpart to electrostatic Bernstein‐Greene‐Kruskal modes. Our analytical model is verified by relevant numerical simulations. Test particle and PIC simulations indeed show that it is a modification of distribution function at small parallel velocities that results in fading away of free energy driving mirror mode. The physical similarity of the mirror and Weibel instabilities is demonstrated. The multipoint satellite measurements in space plasma can be used to validate a proposed scenario.

This paper considers the evolution of a flat svarm of cometary bodies (under the effect of the passage of stars), initially moving in one direction along the circular orbits with radii 1.4×104

Collisionless shocks cannot occur naturally on the earth, because nearly all matter here consists of electrically neutral atoms and molecules. In space, however, high temperatures and ultraviolet radiation from hot stars decompose atoms into their constituent nuclei and electrons, producing a soup of electrically charged particles known as a plasma. Plasma physicists proposed that the collective electrical and magnetic properties of plasmas could produce interactions that take the place of collisions and permit shocks to form. In 1964 the theoretical work found its first experimental confirmation. Norman F. Ness and his colleagues at the Goddard Space Flight Center, using data collected from the iMP-1 spacecraft, detected clear signs that a collisionless shock exists where the solar wind encounters the earth's magnetic field. More recent research has demonstrated that collisionless shocks appear in a dazzling array of astronomical settings. For example, shocks have been found in the solar wind upstream (sunward) of all the planet and comets that have been visited by spacecraft. Violent flares on the sun generate shocks that propagate to the far reaches of the solar system; tremendous galactic outbursts create disruptions in the intergalactic medium that are trillions of times larger. In addition, many astrophysicists think thatmore » shocks from supernova explosions in our galaxy accelerate cosmic rays, a class of extraordinarily energetic elementary particles and atomic nuclei that rain down on the earth from all directions.« less

The Burgers equation with a driver corresponding to a few unstable harmonics and small viscosity is considered. It is shown that this equation has a traveling wave solution looking like a periodic sequence of shocks.

The influence of a perturbation of the Hamiltonian on the process of the random walk of a particle in a phase space with a stochastic web is investigated. The bifurcations connected with such a perturbation are considered. The acceleration of the particle diffusion due to nonresonant perturbation and the transformation of the stochastic web to the strong anisotropic form for the resonant perturbation are shown.

Computer simulations are presented for a new object of chaos, stochastic jets, for a steady flow with five-fold symmetry with the Beltrami property. Lagrangian chaos of streamlines can reveal itself in the existence of huge flights which is connected with the asymptotic laws of anomalous transport of passive particles.

Plasma wave activity in the neighborhood of the Martian bow shock were measured for the first time by the Soviet spacecraft Phobos-2 in a wide frequency range from dc to 150 kHz. The wave activity varied in character as the spacecraft moved across different plasma regions: in the neigborhood of the Martian bow shock, inside the magnetosheath and in the tail region. In this paper we provide suggestions for the processes responsible for these plasma waves. The most interesting peculiarities of the wave activity around Mars is the sharp increse of wave intensity in the magnetosheath region. This increase is attributed to two different physical mechanisms. High frequency waves are excited at the shock front due to currents flowing along the front; these ion acoustic waves are convected inside by the solar wind. The low frequency waves (∼100 Hz) close to the inside boundary were, we believe, generated by heavy Martian ions diffusing through the planetopause into the magnetosheath.

An overview of data concerning the mantle and planetosphere regions of Mars and Venus is presented, emphasizing data from the Phobos 2 mission. It is shown that there are significant similarities between the mantle/planetosphere regions on the two planets. These similarities include a transition region between the magnetosheath and the ionosphere dominated by heavy, planetary ions, and a transition region in which the electron population is different from both the shock solar wind and the photoelectron populations. Also, on both planets, a magnetic signature near the transition boundary and the presence of low frequency electric waves within the transition region are observed.

The width of the stochastic web is calculated for different cases of its symmetry. Exponential and preexponential factors are found. The correction of the asymptotic expansion due to the deformation of the stochastic web is included. The comparison of analytical results with the results of numerical simulation is made. The diffusion of particles along the stochastic web is investigated.

Computer simulation experiments are presented showing that the streamline transport properties strongly depend on the flow symmetry and on the phase portrait topology of the streamlines. The motion of a liquid particle inside the channels of the stochastic web demonstrates the random walk with Levy flights.

This report concerns a fundamentally new high-sensitive magnetic resonance method for detection of short-lived species - radical pairs, radical ion pairs, biradicals and radicals - the method of stimulated nuclear polarization (SNP). The SNP-method is based on the resonance mw-field effects on nuclear polarization in the products of the radical reactions. Using this method one can obtain information on the ESR spectrum of intermediate short-lived RP and on the channels of reaction product format ion.

(1990). Fissile materials and weapon design. Science & Global Security: Vol. 1, Detecting Nuclear Warheads, pp. 255-263.