Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer

³He (helium-3) in the lunar regolith implanted by the solar wind is one of the most valuable resources because of its potential as a fusion fuel. The abundance of ³He in the lunar regolith is related to solar wind flux, lunar surface maturity and TiO₂ content, etc. A model of solar wind flux, which takes account of variations due to shielding of the nearside when the Moon is in the Earth's magnetotail, is used to present a global distribution of relative solar wind flux over the lunar surface. Using Clementine UV/VIS multispectral data, the global distribution of lunar surface optical maturity (OMAT) and the TiO₂ content in the lunar regolith are calculated. Based on Apollo regolith samples, a linear relation between ³He abundance and normalized solar wind flux, optical maturity, and TiO₂ content is presented. To simulate the brightness temperature of the lunar surface, which is the mission of the Chinese Chang-E project's multichannel radiometers, a global distribution of regolith layer thickness is first empirically constructed from lunar digital elevation mapping (DEM). Then an inversion approach is presented to retrieve the global regolith layer thickness. It finally yields the total amount of ³He per unit area in the lunar regolith layer, which is related to the regolith layer thickness, solar wind flux, optical maturity and TiO₂ content, etc. The global inventory of ³He is estimated as 6.50×¹⁰⁸ kg, where 3.72×¹⁰⁸ kg is for the lunar nearside and 2.78×¹⁰⁸ kg is for the lunar farside.     

Ultracompact HII regions: the impact of newly formed massive stars on their environment

Summary Ultracompact (UC)HII regions are manifestations of newly formed massive stars that are still embedded in their natal molecular cloud. They are among the brightest and most luminous single objects in the Galaxy at far infrared and radio wavelengths. Recent high spatial resolution studies, particularly at radio wavelengths, have greatly contributed to our understanding of these dynamic objects and the impact they have on their environment. A summary is given of our current understanding of the physical properties, morphologies, dynamics, number and distribution in the Galaxy, and molecular environments of UCHII regions. Recent models of the circumnebular dust imply that the graphite/silicate abundance ratio is about half that of dust in the diffuse interstellar medium. The dust cocoons are large, cool, and optically thick shortward of a few microns. There are apparently between 1700 and 3000 UCHII regions in the Galaxy. This represents 10–20% of the total O star population. There are too many UCHII regions (just counting those studied with the VLA) to be consistent with the short dynamical lifetimes of this very compact stage of evolution. Both the morphologies and the large number can be understood if UC HII regions are bow shocks. Models of stellar wind supported bow shocks are discussed and consequences for the dynamics and morphologies of the ionized and molecular gas are explored.     

A systematic radial velocity survey of the HII regions IC 1318a and HS 191

The results of a systematic radial velocity survey of two Hii regions in the Cygnus-X complex are presented. The [Nii] emission line components obtained at many positions over each object have been compared and correlated with other phenomena. It is suggested that they are probably connected objects and may be part of a giant shell or cylinder.     

The X—ray Background from the Warm Gas of the Galactic Halo

LETTERS1 INTRODUCTIONIn the hierarchical scenario of structure formation, massive dark ha1os fOrm by gravitationalaggregation of individual low-mass objects, whi1e the stel1ar disks of spiral galaxies like theMilky Way form by accretion of gas which cools and falls onto the galaxies from an extendedsurrounding reservoir. FOr a massive galaxy of M ~ 10"MO, the surrounding gas can be heatedto temperature of T ~ 106 K by gravitational1y-driven shocks, the dominant cooling is thus dueto …     

H166α Emission as a Tracer of the Warped Ionized Gas Layer in the Northern Galaxy

Observations of the H166 α recombination line were made with the 43 m antenna of the National Radio Astronomy Observatory (NRAO), in Green Bank, West Virginia, United States of America. The United States of results of the observations in the galactic longitude range 60−<l<90<− at each degree in galactic longitude and galactic latitudes b=0.0, b=+0.5−, b=+1.5−,b=−0.5− ,b=−1.5−, together with observations at l=81− and l=83− for b=−4− to b=+5−, each degree in galactic latitude, clearly show more recombination line emission for positive galactic latitudes than for negative galactic latitudes. We interpret these results as a clear evidence of the warp of the low density ionized gas layer towards positive latitudes in the Northern Galactic Plane. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of a thin weak layer covering a basalt block on the impact cratering process

To clarify the effect of a surface regolith layer on the formation of craters in bedrock, we conducted impact-cratering experiments on two-layered targets composed of a basalt block covered with a mortar layer. A nylon projectile was impacted on the targets at velocities of 2 and 4 km s^?1, and we investigated the crater size formed on the basalt. The crater size decreased with increased mortar thickness and decreased projectile mass and impact velocity. The normalized crater volume, π_V, of all the data was successfully scaled by the following exponential equation with a reduction length λ₀: ${\pi }_{\text{V}}=b_0{\pi }_{\text{Y}}^{-b_1}\exp (-\lambda /{\lambda }_0)$, where λ is the normalized thickness T/L_p, T and L_p are the mortar thickness and the projectile length, respectively, b₀ and b₁ are fitted parameters obtained for a homogeneous basalt target, 10^?2.7±0.7 and ?1.4 ± 0.3, respectively, and λ₀ is obtained to be 0.38 ± 0.03. This empirical equation showing the effect of the mortar layer was physically explained by an improved non-dimensional scaling parameter, ${\pi }_{\text{Y}}^1$, defined by ${\pi }_{\text{Y}}^1=Y/({\rho }_{\text{t}}{u}_{\text{p}}^2)$, where u_p was the particle velocity of the mortar layer at the boundary between the mortar and the basalt. We performed the impact experiments to obtain the attenuation rate of the particle velocity in the mortar layer and derived the empirical equation of $\frac{u_{\text{p}}}{v_{\text{i}}}=0.50\exp \left(-\frac{\lambda }{1.03}\right)$, where v_i is the impact velocity of the projectile. We propose a simple model for the crater formation on the basalt block that the surface mortar layer with the impact velocity of u_p collides on the surface of the basalt block, and we confirmed that this model could reproduce our empirical equation showing the effect of the surface layer on the crater volume of basalt.     

Magnetic modeling and tomography: First steps towards a consistent reconstruction of the solar corona

We undertake a first attempt towards a consistent reconstruction of the coronal magnetic field and the coronal density structure. We consider a stationary solar corona which has to obey the equations of magnetohydrostatics. We solve these equations with help of a newly developed optimization scheme. As a first step we illustrate how tomographic information can be included into the reconstruction of coronal magnetic fields. In a second step we use coronal magnetic field information to improve the tomographic inversion process. As input the scheme requires magnetic field measurements on the photosphere from vector-magnetographs and the line-of-sight integrated density distribution from coronagraphs. We test our codes with well-known analytic magnetohydrostatic equilibria and models. The program is planned for use within the STEREO mission.     

The origin of spatial intermittency in the galaxy distribution

The dynamical equations describing the evolution of a self-gravitating fluid can be rewritten in the form of a Schrödinger equation coupled to a Poisson equation determining the gravitational potential. This approach has a number of interesting features, many of which were pointed out in a seminal paper by Widrow & Kaiser. In particular we show that this approach yields an elegant reformulation of an idea of Jones concerning the origin of lognormal intermittency in the galaxy distribution.     

The spatial distribution of volatiles in the Martian hydrolithosphere

In order to quantify the spatial distribution of volatiles on Mars, 2600 fluidized ejecta craters have been systematically measured, classified and mapped over the planet Mars, using 1 : 2 M scale USGS photomosaics. The latitudinal distribution of ejecta craters reveals that flower ejecta deposits (Type 1), together with low mobility ejecta, are frequently observed in the equatorial region and on ridged plains. Rampart craters (Type 2), with high mobility ejecta, occur at mid latitudes and exhibit a spatial relationship with polygonal patterns and pseudocrater areas. The increase of ejecta mobility with latitude attests for a concentration of volatiles at high latitudes. Statistical analysis shows that cratered uplands and ridged plains contain less volatile material near the surface than the underlying materials. In Chryse Planitia and Utopia Planitia the statistical study and the spatial relationships between polygonally fractured patterns, pseudocraters and the great number of high mobility ejecta deposits suggest the presence of a water-rich alluvial deposit close to the surface near the mouth of Chryse and Elysium channels. This result explains, on a more quantitative basis, the idea that fractured patterns were preferentially developed in a volatile-rich sedimentary deposits. The behaviour of volatiles, at 41 S, 257 W near Reull Vallis, exhibits a strong anomaly, with the presence of an abnormally volatile rich layer close to the surface.     

The mass distribution in the innermost regions of spiral galaxies

We use high-spatial resolution (100 pc) rotation curves of 83 spiral galaxies to investigate the mass distribution of their innermost kpc. We show that, in this region, the luminous matter completely accounts for the gravitational potential and no dark component is required. The derived I-band disk mass-to-light ratios agree well with those obtained from population synthesis models and correlate with color in a similar way. We find strict upper limits of 10⁷ M for the masses of compact bodies at the center of spirals, ruling out that these systems host the remnants of the quasar activity.     

The spatial distribution of polar hydrogen deposits on the Moon

A new analysis of the Lunar Prospector epithermal neutron data is presented, providing an improved map of the distribution of hydrogen near to the lunar poles. This is achieved using a specially developed pixon image reconstruction algorithm to deconvolve the instrumental response of the Lunar Prospector's neutron spectrometer from the observed data, while simultaneously suppressing the statistical noise. The results show that these data alone require the hydrogen to be concentrated into the cold traps at up to 1 wt% water-equivalent hydrogen. This combination of localisation and high concentration suggests that the hydrogen is present either in the form of a volatile compound or as solar wind protons implanted into small regolith grains.     

The large-scale pattern formed by the spatial distribution of granules

The spatial distribution of granule sizes at the surface of the sun is investigated. Granules have been separated into two classes: those larger than 1.37 and those smaller, where 1.37 is the critical scale defined by Roudier and Muller (1986). It is found that granules are not distributed at random: large granules appear to be clustered, forming a cellular pattern with a characteristic scale of 7; small granules form a similar and complementary pattern. These patterns are probably related to the mesogranulation.     

Young open star clusters: The spatial distribution of metallicity in the solar neighborhood

We perform a comparative analysis of the spatial distribution of young (<50 Myr) open star clusters and field Cepheids with different metallicities. A significant fraction of young clusters are shown to have low metallicities atypical of field Cepheids. Both types of objects exhibit approximately equal (in magnitude) negative radial metallicity gradients, while their azimuthal metallicity gradients differ outside the error limits and have opposite signs. Among the stellar complexes identified by young clusters, the most metal-poor clusters are grouped in the Perseus complex. It is the clusters of this complex that are responsible for the radial and azimuthal metallicity gradients among young clusters. The described properties are indicative of a weak mixing of interstellar matter before the onset of star formation there. Significant differences between the spatial distributions of open clusters and field stars with different metallicities suggest different conditions required for the formation of these types of objects.     

The MSDOL Project: Assimilation of Gomos Ozone Data in a 3-D chemistry-transport model

In the frame of the preparation of the use of ENVISAT data, the EEC is supporting the MSDOL project: Monitoring of the Stratospheric Depletion of the Ozone Layer. The purpose is to assimilate the 400 vertical profiles of Ozone recorded each day by the experiment GOMOS (on the future ESA ENVISAT spacecraft ) in a 3-D chemistry-transport model, where the winds are the ECMWF analysis. The sequentially assimilated model will better represent the reality since all single measurements are extrapolated in space and time through chemistry and transport. The assimilated model will serve at least two purposes : the comparison with other data sets, and the estimate of the evolution of ozone as a function of time and space.The 3-D model is derived from the stratospheric chemistry-transport Rose model, in which the internally generated dynamics is replaced by the actual wind field.     

The spatial distribution of pulsars and the spiral structure of the Galaxy

We have looked for and found a possible spatial correlation between the present pulsar distribution and the estimated locations of the spiral arms at earlier epochs. Through a detailed statistical analysis we find a significant correlation between the present distribution of pulsars and the mass distribution (in the spiral arms) expected about 60 Myr ago for a corotation resonance radius of 14kpc. We discuss the implications of this correlation for the minimum mass of the progenitors of pulsars. Interpreting the spread in the locations of pulsars with respect to the past locations of the spiral arms as predominantly due to their space velocities, we derive an average velocity for the pulsar population.     

3-D non-linear evolution of a magnetic flux tube in a spherical shell: The isentropic case

We present recent 3-D MHD numerical simulations of the non-linear dynamical evolution of magnetic flux tubes in an adiabatically stratified convection zone in spherical geometry, using the anelastic spherical harmonic (ASH) code.We seek to understand the mechanism of emergence of strong toroidal fields from the base of the solar convection zone to the solar surface as active regions. We confirm the results obtained in cartesian geometry that flux tubes that are not twisted split into two counter vortices before reaching the top of the convection zone. Moreover, we find that twisted tubes undergo the poleward-slip instability due to an unbalanced magnetic curvature force which gives the tube a poleward motion both in the non-rotating and in the rotating case. This poleward drift is found to be more pronounced on tubes originally located at high latitudes. Finally, rotation is found to decrease the rise velocity of the flux tubes through the convection zone, especially when the tube is introduced at low latitudes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The spatial distribution of 6 centimeter gyroresonance emission from a flaring X-ray loop

We compare simultaneous high resolution soft X-ray and 6 cm images of the decay phase of an M3 X-ray flare in Hale Region 16413. The photographic X-ray images were obtained on an AS & E sounding rocket flown 7 November, 1979, and the 6 cm observations were made with the VLA. The X-ray images were converted to arrays of line-of-sight emission integrals and average temperature throughout the region. The X-ray flare structure consisted of a large loop system of length 1.3 arc min and average temperature 8 × 10⁶ K. The peak 6 cm emission appeared to come from a region below the X-ray loop. The predicted 6 cm flux due to thermal bremsstrahlung calculated on the basis of the X-ray parameters along the loop was about an order of magnitude less than observed. We model the loop geometry to examine the expected gyroresonance absorption along the loop. We find that thermal gyroresonance emission requiring rather large azimuthal or radial field components, or nonthermal gyrosynchrotron emission involving continual acceleration of electrons can explain the observations. However, we cannot choose between these possibilities because of our poor knowledge of the loop magnetic field.