bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation and early evolution of massive black holes
Authors: Madau Piero
Published: May 2007

The astrophysical processes that led to the formation of the first seed black holes and to their growth into the supermassive variety that powers bright quasars at z ∼ 6 are poorly understood. In standard ΛCDM hierarchical cosmologies, the earliest massive holes (MBHs) likely formed at redshift z ≳ 15 at the centers of low-mass (M ≳ 5 × 105 M⊙) dark matter “minihalos”, and produced hard radiation by accretion. FUV/X-ray photons from such “miniquasars” may have permeated the universe more uniformly than EUV radiation, reduced gas clumping, and changed the chemistry of primordial gas. The role of accreting seed black holes in determining the thermal and ionization state of the intergalactic medium depends on the amount of cold and dense gas that forms and gets retained in protogalaxies after the formation of the first stars. The highest resolution N-body simulation to date of Galactic substructure shows that subhalos below the atomic cooling mass were very inefficient at forming stars.
An accretion disk laboratory in the Seyfert 1.9 galaxy NGC 2992
Authors: Yaqoob Tahir , Murphy Kendrah D. , Terashima Yuichi
Published: May 2007

Over twenty five years of X-ray observations of the Seyfert 1.9 galaxy NGC 2992 show that it is a promising test-bed for severely constraining accretion disk models. The previous interpretation of the historical activity of NGC 2992 in terms of the accretion disk slowly becoming dormant over many years and then ‘re-building’ itself is not supported by new data. A recent year-long monitoring campaign with RXTE showed that the X-ray continuum varied by more than an order of magnitude on a timescale of weeks. During the large-amplitude flares the centroid energy of the Fe K emission-line complex became significantly redshifted, indicating that the violent activity was occurring close to the putative central black hole where gravitational energy shifts can be sufficiently large. For the continuum, the Compton-y parameter remains roughly constant despite the large-amplitude luminosity variability, with (kT) τ ∼ 20–50.
Strong gravity effects: X-ray spectra, variability and polarimetry
Authors: Fabian Andrew C.
Published: May 2007

Accreting black holes often show iron line emission in their X-ray spectra. When this line emission is very broad or variable then it is likely to originate from close to the black hole. The theory and observations of such broad and variable iron lines are briefly reviewed here. In order for a clear broad line to be found, one or more of the following have to occur: high iron abundance, dense disk surface and minimal complex absorption.

Several excellent examples are found from observations of Seyfert galaxies and Galactic Black Holes. In some cases there is strong evidence that the black hole is rapidly spinning. Further examples are expected as more long observations are made with XMM-Newton, Chandra and Suzaku. The X-ray spectra show evidence for the strong gravitational redshifts and light bending expected around black holes.
Following the gas flows from nuclear spirals to the accretion disk
Authors: Storchi-Bergmann Thaisa
Published: May 2007

A recent analysis of HST optical images of 34 nearby early-type active galaxies and of a matched sample of 34 inactive galaxies – both drawn from the Palomar survey – shows a clear excess of nuclear dusty structures (filaments, spirals and disks) in the active galaxies. This result supports the association of the dusty structures with the material which feeds the supermassive black hole (hereafter SMBH). Among the inactive galaxies there is instead an excess of nuclear stellar disks. As the active and inactive galaxies can be considered two phases of the “same” galaxy, the above findings and dust morphologies suggest an evolutionary scenario in which external material (gas and dust) is captured to the nuclear region where it settles and ends up feeding the active nucleus and replenishing the stellar disk – which is hidden by the dust in the active galaxies – with new stars. This evolutionary scenario is supported by recent gas kinematics of the inner few hundred parsecs of NGC 1097, which shows streaming motions (with velocities ∼50 km s−1) towards the nucleus along spiral arms. The implied large scale mass accretion rate is much larger than the one derived in previous studies for the nuclear accretion disk, but is just enough to accumulate one million solar masses over a few million years in the nuclear region, thus consistent with the recent finding of a young circumnuclear starburst of one million solar masses within 9 parsecs from the nucleus in this galaxy.
The thermal—viscous disk instability model in the AGN context
Authors: Hameury Jean-Marie , Lasota Jean-Pierre , Viallet Maxime
Published: May 2007

Accretion disks in AGN should be subject to the same disk instability responsible for dwarf novae outbursts and soft X-ray transients in cataclysmic variables (CVs) and LMXBs. It has been suggested that this thermal/viscous instability can account for long term variability of AGNs. We analyze here the application of the DIM to the AGN case, using our adaptive grid numerical code developed in the context of CVs, enabling us to fully resolve the disk radial structure. We show that in AGNs, the width of heating and cooling fronts is so small that they cannot be resolved by standard codes, and that they propagate on time scales much shorter than the viscous time. As a result, transition fronts propagate back and forth in the disk, leading only to small luminosity variations. Truncation of the inner part of the disk by e.g. an ADAF will not alter this result, but enables the presence of quiescent states.
Variations of geometrical and physical characteristics of innermost regions of active galactic nuclei on time-scale of years
Authors: Bochkarev Nikolai G. , Shapovalova Alla I.
Published: May 2007

Several examples of observational evidence of possible variations of geometrical and physical characteristics of the Broad Line Regions (BLR) of AGN on the time-scale of years are listed. Cases of accretion disk size variations and variable input of jets in BLR formation are presented.
Radiation in models with cosmological constant
Authors: Kadlecová Hedvika , Podolský Jiří
Published: May 2007

We analyze the asymptotic directional structure and properties of gravitational field of specific exact solutions belonging to the large family of black hole spacetimes of type D found by Plebański and Demiański. We discuss the structure in the case of de Sitter (Λ>0) and anti–de Sitter (Λ<0) conformal infinity. With the aim of further interpretation, we have found the relation between the structure of the sources (the mass m, the electric e and magnetic g charges, the NUT parameter l, the rotational parameter a, the acceleration α) and the properties of radiation generated by them. In particular, we studied the amplitude of radiation and illustrated it in several figures.
The results of X-ray binary Cyg X-1 investigations based on the optical photometry and high-resolution spectroscopy
Authors: Karitskaya Eugenia A.
Published: May 2007

Selected results of 1994-2004 optical photometric and high-resolution spectral observations including those obtained in the frame of a coordinated CIS countries campaign “Optical Monitoring of Unique Astrophysical Objects” and their comparison with ASM/RXTE X-ray data are briefly reviewed.
Long-term photometry of blazars at Abastumani Observatory
Authors: Kurtanidze Omar M. , Nikolashvili Maria G. , Kimeridze Givi N. , Sigua Lorand A. , Kapanadze Bidzina Z. , Ivanidze Roman Z.
Published: May 2007

We give a brief summary of the ongoing Abastumani Active Galactic Nuclei Monitoring Program started in the May 1997. More than 110000 frames are obtained during more than 1300 nights of observations for about 50 target objects, among them gamma-ray, X-ray and optical blazars. All observations were done in the BVRI bands using ST-6 CCD based photometer attached to the Newtonian focus of 70-cm meniscus telescope.
XMM-Newton study of the spectral variability in NLS1 galaxies
Authors: Ponti G. , Cappi M. , Czerny B. , Goosmann R. W. , Karas V.
Published: May 2007

Preliminary results of the study of the X-ray spectral variability of 12 Narrow Line Seyfert 1 (NLS1) galaxies are presented. Rms spectra are calculated and compared for the whole sample to search for possible variations with black hole mass. A larger sample of AGN is under investigation.
Observational properties of relativistic black hole winds
Authors: Watarai Ken-ya
Published: May 2007

We examine observational properties of relativistic black hole winds as an origin of high luminosity sources such as microquasars and ultra-luminous X-ray sources (ULXs). When strong relativistic wind/outflow happens in the vicinity of the black hole, the wind might form the optically-thick photosphere. Therefore the emission observed in ULXs might come from the photosphere of the wind, not from the accretion disk.

We found that the location of the photosphere is larger than the disk thickness for super-Eddington mass-outflow rates and sub-relativistic wind velocities (v ∼ 0.1–0.2 c). To understand the radiative structure in the high luminosity sources, we should take into account not only the emission from the accretion disk but also the emission from the outflow at the same time.
Ground observation and AMIE‐TIEGCM modeling of a storm‐time traveling ionospheric disturbance
Authors: Shiokawa K. , Lu G. , Otsuka Y. , Ogawa T. , Yamamoto M. , Nishitani N. , Sato N.
Published: May 2007

This paper reports the first comparison between comprehensive observations of equatorward moving traveling ionospheric disturbance at midlatitudes and thermospheric general circulation model with high‐latitude energy input based on data assimilation. A prominent traveling ionospheric disturbance (TID) was observed during the major magnetic storm of 31 March 2001. The TID propagated from north to south over Japan with phase speeds of 370–640 m/s. The assimilative mapping of ionospheric electrodynamics (AMIE) technique was used as input to the thermosphere‐ionosphere‐electrodynamics general circulation model (TIEGCM) to investigate generation and propagation of the observed TID. In the model, two Joule heating enhancements in the high‐latitude dayside sector produced two distinct traveling atmospheric waves (TADs), which propagated to Japan in the midnight sector as enhancements in thermospheric temperature and southward wind speed. The phase speed of the TADs was much faster (∼1100 m/s) in the model, probably due to the overestimation of Joule heating in the model. The second TAD corresponds to the observed prominent TID, while signatures of the first TAD were also seen in the observed ionosonde data. The observed TID was characterized by a decrease in southward wind speed, causing a significant F‐layer height decrease and a temporal enhancement of F‐layer peak density. These characteristics were reproduced by the model as a rarefaction of the second TAD. The temporal enhancement of F‐layer peak density was because of the vertical shear of meridional wind. The absolute value of F‐layer electron density in the model was several factors smaller than that observed, probably because of the underestimation of the supply of O+ ions from the plasmasphere.
Large parallel electric fields, currents, and density cavities in dispersive Alfvén waves above the aurora
Authors: Chaston C. C. , Hull A. J. , Bonnell J. W. , Carlson C. W. , Ergun R. E. , Strangeway R. J. , McFadden J. P.
Published: May 2007

Large parallel electric fields (E∥ > 10 mV/m) are sometimes observed with intense filamentary field‐aligned currents (J∥ > 10 μA/m2 mapped to 100‐km altitude) on transverse scales where kxc/ωpe ≈ 1 above the auroral oval. The ratio of the transverse electric (Ex) and magnetic field (By) variations is approximately the local Alfvén speed and increases with decreasing transverse scale in a manner consistent with inertial Alfvén wave dispersion. These fields are typically observed in association with density cavities. Statistically, it is shown that the depth of the cavities observed over the altitude range from 350 to 4175 km by the Fast Auroral Snapshot (FAST) satellite typically lies between 30 and 50% of the background plasma with 90% depletions being observed for 1% of the recorded events. The wave currents embedded within these cavities exceed 100 μA/m2 for 2% of the ensemble and are typically found over transverse widths of ∼2πλe. Using a fluid description of the plasma, we show statistically that electron pressure gradients provide a probable means for balancing the large E∥ found in these structures with a likely but unknown contribution from anomalous resistivity. Furthermore, we find that the ratio of the average drift speed of the bulk electron plasma (vd) to the electron thermal speed (ve) inside these structures is vd/ve ≥ 0.1 and that in at least 2% of cases veh05d/ve ≥ 1.0. On the basis of recent simulation results and the Bohm criterion for double layer formation, these statistics indicate that the large E∥ sometimes observed in density cavities may occur in double layers driven by the Alfvén wave current.
Global profiles of compressional ultralow frequency wave power at geosynchronous orbit and their response to the solar wind
Authors: Sanny J. , Judnick D. , Moldwin M. B. , Berube D. , Sibeck D. G.
Published: May 2007

We investigate the global local‐time profiles of compressional wave power in three ultralow frequency (ULF) bands corresponding to Pc3, Pc4, and Pc5 pulsations using magnetic field data from the geosynchronous GOES satellites. The global power profiles of the three frequency bands are studied for low, moderate, and high levels of geomagnetic activity based on the Dst index. We also consider the seasonal variation of the ULF power profiles, as well as the effects of solar wind and interplanetary magnetic field (IMF) parameters. For high geomagnetic activity, we find that the greatest power is associated with compressional Pc5 pulsations in the afternoon sector; for low geomagnetic activity, ULF power levels are consistently highest in the tail region. A summer power minimum in all three frequency bands is observed in our study of seasonal variation, while higher power levels occur around local midnight throughout the year. The enhancement of ULF power by high solar wind velocity and pressure is greater for the lower‐frequency waves. Furthermore, solar wind plasma parameters have a significantly greater influence on ULF wave power than IMF parameters like cone angle and northward/southward orientation.
Multispacecraft observations of chorus dispersion and source location
Authors: Breneman Aaron , Kletzing Craig A. , Chum Jaroslav , Santolik Ondrej , Gurnett Donald , Pickett Jolene
Published: May 2007

We report Cluster Wideband Data (WBD) receiver observations of correlated chorus elements with different frequency/time characteristics as seen on multiple spatially separated Cluster spacecraft. Because chorus packets disperse as they propagate, careful comparison of the signals from multiple spacecraft can provide new information about the origin of these waves. A cross‐correlation analysis is used to quantify the dispersive time delay between each frequency of a chorus element as it arrives at Cluster spacecraft pairs. This data cross‐correlation is then compared with a ray‐tracing technique in order to identify source locations that are consistent with the observed delays. We also consider a time‐variable source that emits frequencies that increase as a function of time. This frequency drift rate is adjusted to force the frequency/time variation of the simulated chorus element on a single spacecraft to match that observed. This process yields possible source locations for each spacecraft, whose location and extent are a function of the amount of source frequency emission drift. By requiring the individual spacecraft source regions to intersect with the multispacecraft source regions, a common static source region at L ∼ 3.9 (McIlwain parameter) and MLAT ∼ −5.9° (magnetic latitude) is identified for a single event (event 1) and upper and lower bounds are placed on the amount of source emission frequency drift within the source. No common source region is found for a second event (event 2).
Cluster and DMSP observations of SAID electric fields
Authors: Puhl‐Quinn P. A. , Matsui H. , Mishin E. , Mouikis C. , Kistler L. , Khotyaintsev Y. , Décréau P. M. E. , Lucek E.
Published: May 2007

We report on magnetically conjugate Cluster and the Defense Meteorological Satellite Program (DMSP) satellite observations of subauroral ion drifts (SAID) during moderate geomagnetic activity levels on 8 April 2004. To our knowledge, the field‐aligned separation of DMSP and Cluster (≈28,000 km) is the largest separation ever analyzed with respect to the SAID phenomenon. Nonetheless, we show coherent, subauroral magnetosphere‐ionosphere (MI) coupling along an entire field line in the post‐dusk sector. The four Cluster satellites crossed SAID electric field channels with meridional magnitude EM of 25 mV/m in situ and latitudinal extent ΔΛ ≈ 0.5° in the southern and northern hemispheres near 07:00 and 07:30 UT, respectively. Cluster was near perigee (R ≈ 4 RE) and within 5° (15°) of the magnetic equator for the southern (northern) crossing. The SAID were located near the plasmapause—within the ring current‐plasmasphere overlap region. Downward field‐aligned current signatures were observed across both SAID crossings. The most magnetically and temporally conjugate SAID field from DMSP F16A at 07:12 UT was practically identical in latitudinal size to that mapped from Cluster. Since the DMSP ion drift meter saturated at 3000 m/s (or ∼114 mV/m) and the electrostatically mapped value for EM from Cluster exceeded 300 mV/m, a magnitude comparison of EM was not possible. Although the conjugate measurements show similar large‐scale SAID features, the differences in substructure highlight the physical and chemical diversity of the conjugate regions.
Heat flow in the Republic of Korea
Authors: Kim Hyoung Chan , Lee Youngmin
Published: May 2007

We report 111 new heat flow data in the Republic of Korea and combine these with previously reported 248 heat flow data to construct the heat flow map of the Republic of Korea. The mean geothermal gradient of the Republic of Korea is 25.1°C/km; mean heat flow of the Republic of Korea is 60 ± 11 mW/m2. The southeastern part, the central western part, and the northeastern part of the Republic of Korea show high heat flow values. In terms of the lithology, heat flow is 71 ± 2 mW/m2 for the area of sedimentary rock, 68 ± 2 mW/m2 for the sedimentary/volcanic rock area, 67 ± 1 mW/m2 for the plutonic rock area, and 62 ± 2 mW/m2 for the metamorphic rock area. In the geological time sequence, heat flow is 78 ± 5 mW/m2 for the Cenozoic strata, 68 ± 1 mW/m2 for the Mesozoic, 65 ± 3 mW/m2 for the Paleozoic strata, 67 ± 8 mW/m2 for the Proterozoic strata, and 62 ± 2 mW/m2 for the Archean strata. In the aspect of the Moho depth, the shallow Moho depth area tends to have higher heat flow values than the area of the thick crust.
Aftershock asymmetry on a bimaterial interface
Authors: Rubin Allan M. , Ampuero Jean‐Paul
Published: May 2007

To better understand the asymmetric distribution of microearthquake aftershocks along the central San Andreas fault, we study dynamic models of slip‐weakening ruptures on an interface separating differing elastic half‐spaces. Subshear ruptures grow as slightly asymmetric bilateral cracks, with larger propagation velocities, slip velocities, and normal stress changes at the rupture front moving in the direction of slip of the medium with the lower shear wave speed (the southeast front, in the context of the San Andreas). When the SE front encounters a stress barrier, the tensile stress perturbation behind the rupture front continues forward and for a wide range of barrier strengths nucleates a dying slip pulse. This slip pulse smooths the stress field and reduces the static stress change beyond the SE front. Furthermore, because the tensile stress that carried the slip pulse into the barrier is a purely dynamic phenomenon, the SE rupture front can be left far below the failure threshold, while the NW front remains quite close to failure. Both mechanisms could contribute to the observed aftershock asymmetry. Formation of a robust slip pulse requires a peak tensile stress perturbation that approaches the nominal strength drop of the slip‐weakening law. To achieve this while minimizing off‐fault damage requires either substantial velocity contrasts or small reductions in friction. The simulations also show a pronounced asymmetry in the timescales over which barriers to the SE and NW experience increasing stresses, a result that has implications for the asymmetric distribution of subevents in compound earthquakes.
Nonuniform prestress from prior earthquakes and the effect on dynamics of branched fault systems
Authors: Duan Benchun , Oglesby David D.
Published: May 2007

To examine the effects of branched fault geometry on the dynamics of fault systems in the long term, we perform multicycle simulations on generic faulting models. An explicit finite element algorithm is used to simulate spontaneous dynamic rupture of earthquakes. The fault stress during the interseismic period is evaluated by an analytical viscoelastic model. We find that the fault prestress field becomes highly nonuniform near the branch point and on the two branch segments over multiple earthquake cycles, owing to the branched fault geometry and stress interaction between the two segments. The principal prestress on faults rotates over multiple earthquake cycles and departs from the regional stress field significantly near the branch point. After a number of earthquake cycles, the branched fault systems evolve to a steady state in which several patterns of the fault prestress and earthquake rupture repeat. The nonuniform prestress developed from previous earthquakes has large effects on the rupture and slip patterns. Several different rupture scenarios can occur on a given branched fault system. In addition, backward branching can occur in the nonuniform prestress field, either driven by slip on the “stem” of the fault system or through a triggering mechanism. These modeling results may have important implications for understanding fault‐branching behavior observed in the 1992 Landers, the 1999 Hector Mine, and the 2002 Denali fault earthquakes and for seismic hazard analysis in the areas where branched fault systems exist.
Source characteristics of oxygenated volatile organic compounds and hydrogen cyanide
Authors: Shim Changsub , Wang Yuhang , Singh Hanwant B. , Blake Donald R. , Guenther Alex B.
Published: May 2007

Airborne trace gas measurements from Transport and Chemical Evolution over the Pacific (TRACE‐P), Pacific Exploratory Mission (PEM)‐Tropics B, and Intercontinental Chemical Transport Experiment‐North America (INTEX‐NA) experiments are analyzed to examine the major source factors contributing to the observed variabilities of oxygenated volatile organic compounds and cyanides. The positive matrix factorization method is applied to coincident measurements of 11 chemicals including CH3OH, CH3COCH3, CH3CHO, C2H2, C2H6, i‐C5H12, CO, CH3Cl, and CHBr3. Measurements of HCN and CH3CN are available for TRACE‐P and INTEX‐NA. We identify major source contributions from the terrestrial biosphere, biomass burning, industry/urban regions, and oceans. Spatial and back trajectory characteristics of these factors are examined. On the basis of TRACE‐P and PEM‐Tropics B data, we find a factor that explains 80–88% of the CH3OH variability, 20–40% of CH3COCH3, 7–35% of CH3CHO, and 41% of HCN, most likely representing the emissions from terrestrial biosphere. Our analysis suggested that biogenic emissions of HCN may be significant. Cyanogenesis in plants is likely a major emission process for HCN, which was not fully accounted for previously. Larger contributions than previous global estimations to CH3COCH3 and CH3CHO by biomass burning and industry/urban sources likely reflect significant secondary production from volatile organic compound oxidation. No evidence was found for large emissions of CH3COCH3 from the ocean. The oceanic CH3CHO contribution implies large regional variations.
Long‐range transport and tropospheric ozone variability in the western Mediterranean region during the Intercontinental Transport of Ozone and Precursors (ITOP‐2004) campaign
Authors: Ravetta F. , Ancellet G. , Colette A. , Schlager H.
Published: May 2007

Two ground‐based ozone lidars have been operated at Observatoire de Haute Provence (OHP) for 11 days during the Intercontinental Transport of Ozone and Precursors (ITOP‐2004) measurement campaign. Ozone and scattering ratio vertical profiles have been measured from the boundary layer up to the tropopause. At first order, tropospheric ozone temporal variability is due to local pollution within the planetary boundary layer and to stratosphere‐troposphere exchange. Remaining ozone rich layers within the free troposphere are related to long‐range transport processes. Transport pathways are discussed combining Lagrangian particle dispersion modeling analysis and upstream airborne in situ measurements of the chemical composition of these air masses. High ozone and CO mixing ratios measured within polluted plumes aboard the aircraft correspond to ozone and aerosol layers seen by the lidar. Most of these layers have their origin in North America where they are uplifted either by forest fires or by warm conveyor belts in the vicinity of frontal regions. During the campaign, these polluted and thin (<1 km) layers remain coherent and are transported in a Lagrangian manner over the Atlantic Ocean. The layers observed above OHP in the lower free troposphere exhibit ozone mixing ratio 50% larger than background values. With an ozone content of 3 to 6 Dobson Units, these layers increase by 5 to 10% the background tropospheric ozone column.
Four‐dimensional data assimilation experiments with International Consortium for Atmospheric Research on Transport and Transformation ozone measurements
Authors: Chai Tianfeng , Carmichael Gregory R. , Tang Youhua , Sandu Adrian , Hardesty Michael , Pilewskie Peter , Whitlow Sallie , Browell Edward V. , Avery Melody A. , Nédélec Philippe , Merrill John T. , Thompson Anne M. , Williams Eric
Published: May 2007

Ozone measurements by various platforms during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) operations in the summer of 2004 are assimilated into the STEM regional chemical transport model (CTM). Under the four‐dimensional variational data assimilation (4D‐Var) framework, the model forecast (background) error covariance matrix is constructed using both the so‐called NMC (National Meteorological Center, now National Centers for Environmental Prediction) method and the observational (Hollingworth‐Lönnberg) method. The inversion of the covariance matrix is implemented using truncated singular value decomposition (TSVD) approach. The TSVD approach is numerically stable even with severely ill conditioned vertical correlation covariance matrix and large horizontal correlation distances. Ozone observations by different platforms (aircraft, surface, and ozonesondes) are first assimilated separately. The impacts of the various measurements are evaluated on their ability to improve the predictions, defined as the information content of the observations under the current framework. In the end, all observations are assimilated into the CTM. The final analysis matches well with observations from all platforms. Assessed with all the observations throughout the boundary layer and midtroposphere, the model bias is reduced from 11.3 ppbv for the base case to −1.5 ppbv. A reduction of 10.3 ppbv in root mean square error is also seen. In addition, the potential of improving air quality forecasts by chemical data assimilation is demonstrated. The effect of assimilating ozone observations on model predictions of other species is also shown.
Context Camera Investigation on board the Mars Reconnaissance Orbiter
Authors: Malin Michael C. , Bell James F. , Cantor Bruce A. , Caplinger Michael A. , Calvin Wendy M. , Clancy R. Todd , Edgett Kenneth S. , Edwards Lawrence , Haberle Robert M. , James Philip B. , Lee Steven W. , Ravine Michael A. , Thomas Peter C. , Wolff Michael J.
Published: May 2007

The Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) is a Facility Instrument (i.e., government‐furnished equipment operated by a science team not responsible for design and fabrication) designed, built, and operated by Malin Space Science Systems and the MRO Mars Color Imager team (MARCI). CTX will (1) provide context images for data acquired by other MRO instruments, (2) observe features of interest to NASA's Mars Exploration Program (e.g., candidate landing sites), and (3) conduct a scientific investigation, led by the MARCI team, of geologic, geomorphic, and meteorological processes on Mars. CTX consists of a digital electronics assembly; a 350 mm f/3.25 Schmidt‐type telescope of catadioptric optical design with a 5.7° field of view, providing a ∼30‐km‐wide swath from ∼290 km altitude; and a 5000‐element CCD with a band pass of 500–700 nm and 7 μm pixels, giving ∼6 m/pixel spatial resolution from MRO's nearly circular, nearly polar mapping orbit. Raw data are transferred to the MRO spacecraft flight computer for processing (e.g., data compression) before transmission to Earth. The ground data system and operations are based on 9 years of Mars Global Surveyor Mars Orbiter Camera on‐orbit experience. CTX has been allocated 12% of the total MRO data return, or about ≥3 terabits for the nominal mission. This data volume would cover ∼9% of Mars at 6 m/pixel, but overlapping images (for stereo, mosaics, and observation of changes and meteorological events) will reduce this area. CTX acquired its first (instrument checkout) images of Mars on 24 March 2006.
Space‐fractional advection‐dispersion equations with variable parameters: Diverse formulas, numerical solutions, and application to the Macrodispersion Experiment site data
Authors: Zhang Yong , Benson David A. , Meerschaert Mark M. , LaBolle Eric M.
Published: May 2007

To model the observed local variation of transport speed, an extension of the homogeneous space‐fractional advection‐dispersion equation (fADE) to more general cases with space‐dependent coefficients (drift velocity V and dispersion coefficient D) has been suggested. To provide a rigorous evaluation of this extension, we explore the underlying physical meanings of two proposed, and one other possible form, of the fADE by using the generalized mass balance law proposed by Meerschaert et al. (2006). When the classical Fick's law is replaced by its generalized form in the first‐order mass conversation law, the original fADE with constant parameters extends to the advection‐dispersion equation (ADE) with fractional flux (denoted as FF‐ADE). When the net inflow of dispersive flux is from nonlocal concentration gradients following a fractional divergence, we get the ADE with fractional divergence (FD‐ADE). When the total net inflow from both nonlocal advection and nonlocal concentration gradients follows a fractional form, the fADE contains fully fractional divergence (FFD‐ADE). These three fADEs with constant parameters can also be obtained by proper choice of the two memory kernels in the nonlocal dispersive constitutive theory proposed by Cushman et al. (1994), while the space‐variable fADEs correspond to the conditional nonlocal theory proposed by Neuman (1993) after specifying the general (Lévy‐type) functional form of the random distribution. The corresponding Langevin Markov models can be found in many cases, where the Lagrangian stochastic processes can be conditioned directly on local aquifer properties at any practical, measurable level and resolution. The resulting Lagrangian random‐walk particle tracking methods, along with previous numerical solutions using implicit Euler finite differences, distinguish and elucidate the plume behavior described by these fADEs. The fractional models are applied to fit the tritium plumes measured at the Macrodispersion Experiment test site. When the local parameters gleaned from the hydraulic conductivity (K) distribution are varied even slightly (i.e., a two‐zone model), allowing the use of observed hydraulic conditions at the site, the model fits are well within the variability of the data. The extended fADEs describe the fast and space‐dependent leading edges of measured plumes in the regional‐scale alluvial system, which was underestimated and could not be fully captured by the original fADE with constant parameters. Applications also favor the FD‐ADE model because of the ease of implementation and consistency with previous analysis of the K statistics.
Magnitudes of submarine groundwater discharge from marine and terrestrial sources: Indian River Lagoon, Florida
Authors: Martin Jonathan B. , Cable Jaye E. , Smith Christopher , Roy Moutusi , Cherrier Jennifer
Published: May 2007

Magnitudes of terrestrial (fresh) and marine (saline) sources of submarine groundwater discharge (SGD) are estimated for a transect across Indian River Lagoon, Florida. Two independent techniques (seepage meters and pore water Cl− concentrations) show terrestrial SGD decreases linearly to around 22 m offshore, and these techniques, together with a model based on the width of the outflow face, indicate a cumulative discharge of between 0.02 and 0.9 m3/d per meter of shoreline. Seepage meters and models of the deficiencies in 222Rn activity in shallow sediments indicate marine SGD discharges of roughly 117 m3/d per meter of shoreline across the entire 1800‐m‐wide transect. Two surface streams nearest the transect have an average discharge of about 28 m3/d per meter of shoreline. Marine SGD is thus 4 times greater then surface water discharge and more than 2 orders of magnitude greater than terrestrial SGD. The magnitude of the terrestrial SGD is limited by the amount of regional precipitation, evaporation, recharge, and groundwater usage, while marine SGD is limited only by processes circulating marine water into and out of the sediments. The large magnitude of marine SGD means that it could be important for estuarine cycling of reactive components such as nutrients and metals with only slight modification from estuarine water compositions. The small magnitude of terrestrial SGD means that large differences from estuarine water composition would be required to affect chemical cycling.
Report details climate change effects on cultural sites
Authors: Zielinski Sarah
Published: May 2007

A new report from UNESCO (United Nations Educational, Scientific,and Cultural Organization) details how 26 World Heritage sites could be affected by coming climate changes. The 26 examples, which are meant to be representative of therange of threats to the 830 sites inscribed in the World Heritage List, are divided into five types: archaeological sites, glaciers, historiccities and settlements, marine biodiversity,and terrestrial biodiversity. Some of the examples include the Great Barrier Reef, which is expected to experience more frequent episodes of coral bleaching; Timbuktuin Mali, threatened by desertification; and the Chavin Archaeological Site in the Peruvian Central Andes, one of the earliest and best‐known pre‐Columbian sites, which flooding. The report, “Case Studies on ClimateChange and World Heritage,” is availableat http://whc.unesco.org/documents/publLclimatechange.pdf
Ozone sensor restored to weather satellite
Authors: Anonymous
Published: May 2007

A sensor for measuring ozone will be included on the National Polar‐Orbiting Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite, NASA and NOAA announced on 11 April. The Ozone Mapping and Profiler Suite (OMPS) Limb will measure the vertical distribution of ozone in the atmosphere. A U.S. National Academies committee recommended the restoration of the OMPS Limb to the NPOESS program earlier this year in its Earth science decadal survey (see Eos 88(13), 2007). Restoration of the OMPS Limb to the NPOESS program is contingent upon the cost of the instrument. The NPP satellite is scheduled to launch in 2009, and the first NPOESS satellite is scheduled for 2013.
First 3‐D images of the Sun
Authors: Kumar Mohi
Published: May 2007

NASA's twin Solar Terrestrial Relations Observatory (STEREO) spacecraft have produced the first three‐dimensional images of the Sun. The images, released on 23 April, will allow scientists to better understand and model solar storms and the drivers of adverse space weather.

Launched on 25 October 2006, the STEREO spacecraft circle the Sun close to Earth's orbit, and are separating from each other on their orbital arc by about 45 degrees per year. Currently, the offset between the spacecraft has grown to the point where simultaneous views of the Sun from each spacecraft provide depth perception when combined, similar to the eyes on a person's face.
Issues in planetary chronology
Authors: Barlow Nadine G. , Schenk Paul , Bierhaus E. Beau
Published: May 2007

The ‘Workshop on Surface Ages and Histories: Issues in Planetary Chronology’ brought together researchers from the impact cratering, radiometric analysis, and numerical modeling communities to discuss the current status of chronologic techniques and identify future research directions.

Heavily cratered terrains suggest that the inner solar system impact rate was much higher 3.8–4.4 Ga ago (1 Ga = 109 years). Impact rates declined after this late heavy bombardment (LHB) period to a level that has been approximately constant for the past 3.8 Ga. A major question is whether the LHB was a gradual decline or a spike near 4.0 Ga. Dynamical modeling of outer planet migrations reveals a mechanism for perturbing material into the inner solar system between 3.8 and 4.0 Ga. Geochronologic evidences from the Moon, Earth, and asteroids also support a cataclysmic LHB.
Did an earthquake trigger the May 2006 eruption of the Lusi Mud volcano?
Authors: Manga Michael
Published: May 2007

On 29 May 2006, a mud volcano, unofficially named ‘Lusi,’ erupted in the Indonesian city of Sidoarjo, in eastern Java, covering an area of several square kilometers with mud [Davies et al., 2007] and displacing more than 24,000 people [Cyranoski, 2007]. Two days earlier, a magnitude 6.3 earthquake occurred approximately 250 kilometers to the southeast. A 2800‐meter‐deep exploratory gas well, located about 200 meters from the mud eruption, experienced control problems within 5–7 hours of the earthquake (R.J. Davies, personal communication, 2007) indicating changes in fluid pressures soon after this earthquake. This earthquake is coincident with changes in eruptive behavior at nearby magmatic volcanoes [Harris and Ripepe, 2007; Walter et al., 2007]. Did the earthquake trigger the eruption of the Lusi mud volcano?
Landslides: Processes, Prediction, and Land Use [An interview with the author]
Authors: Kumar Mohi
Published: May 2007

As population grows and land use needs change, humans become more vulnerable to landslide hazards. An AGU book, Landslides: Processes, Prediction, and Land Use, written by Roy C. Sidle and Hirotaka Ochiai, suggests that different human activities exacerbate landslide risk, and details current methods in landslide prediction and modeling techniques.

In this issue, Eos talks with Sidle. Sidle has studied landslides for nearly 30 years and is currently head of the Slope Conservation Section at Kyoto University's Disaster Prevention Research Institute (Japan).
Ozone mini‐hole over southwestern Spain during January 2004: Influence over ultraviolet radiation
Authors: Antón M. , Cancillo M. L. , Serrano A. , Vaquero J. M. , García J. A.
Published: May 2007

During the last decades, extremely low total ozone events of small spatial extension, named ozone mini‐hole, have been reported in the Northern Hemisphere. A few ozone mini‐hole episodes, which last only few days, were observed over southwestern Spain during 2004. In this work, these extreme events have been detected using TOMS satellite instrument. Additionally, the UV solar radiation was measured in three cities: Badajoz, Cáceres, and Plasencia. The most intensive episode occurred on 10 January 2004 when total ozone amount values decreased to 189–200 DU. These values represent a decrease greater than 33% with respect to the mean values registered in these cities during 1996–2005. In this paper, firstly we analyse the origin of the ozone mini‐hole episode which is related to two atmospheric dynamics processes. Secondly, the influence of these extreme events on ultraviolet radiation recorded under cloud‐free conditions in southwestern Spain is described. A great increase in UV erythemal radiation measurement was recorded on 10 January 2004, between 43% and 75% with respect to values measured on 10 January 2003 and 10 January 2005.
Wintertime warming of an Arctic shelf in response to large‐scale atmospheric circulation
Authors: Cottier F. R. , Nilsen F. , Inall M. E. , Gerland S. , Tverberg V. , Svendsen H.
Published: May 2007

Observations on the West Spitsbergen Shelf have shown that the dynamic response of the shelf to wind forcing has a profound effect on the heat content of the water. Hydrographic and atmospheric data have been analysed with respect to the relative importance of surface heat fluxes and advective processes on ocean temperature. During the Arctic winter of 2005/06 periods of sustained along‐shelf winds generated upwelling and cross‐shelf exchange causing extensive flooding of the coastal waters with warm Atlantic Water from the West Spitsbergen Current. The winter temperature of the West Spitsbergen Shelf reverted to that typical of fall, interrupting the normal cycle of sea ice formation in the region.
Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect
Authors: Yergeau Etienne , Kang Sanghoon , He Zhili , Zhou Jizhong , Kowalchuk George A
Published: May 2007

Soil-borne microbial communities were examined via a functional gene microarray approach across a southern polar latitudinal gradient to gain insight into the environmental factors steering soil N- and C-cycling in terrestrial Antarctic ecosystems. The abundance and diversity of functional gene families were studied for soil-borne microbial communities inhabiting a range of environments from 51°S (cool temperate – Falkland Islands) to 72°S (cold rock desert – Coal Nunatak). The recently designed functional gene array used contains 24 243 oligonucleotide probes and covers >10 000 genes in >150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance and organic contaminant degradation (He et al. 2007). The detected N- and C-cycle genes were significantly different across different sampling locations and vegetation types. A number of significant trends were observed regarding the distribution of key gene families across the environments examined. For example, the relative detection of cellulose degradation genes was correlated with temperature, and microbial C-fixation genes were more present in plots principally lacking vegetation. With respect to the N-cycle, denitrification genes were linked to higher soil temperatures, and N2-fixation genes were linked to plots mainly vegetated by lichens. These microarray-based results were confirmed for a number of gene families using specific real-time PCR, enzymatic assays and process rate measurements. The results presented demonstrate the utility of an integrated functional gene microarray approach in detecting shifts in functional community properties in environmental samples and provide insight into the forces driving important processes of terrestrial Antarctic nutrient cycling.
Conserved roles of Sam50 and metaxins in VDAC biogenesis
Authors: Kozjak‐Pavlovic Vera , Ross Katharina , Benlasfer Nouhad , Kimmig Sonja , Karlas Alexander , Rudel Thomas
Published: May 2007

Voltage‐dependent anion‐selective channel (VDAC) is a β‐barrel protein in the outer mitochondrial membrane that is necessary for metabolite exchange with the cytosol and is proposed to be involved in certain forms of apoptosis. We studied the biogenesis of VDAC in human mitochondria by depleting the components of the mitochondrial import machinery by using RNA interference. Here, we show the importance of the translocase of the outer mitochondrial membrane (TOM) complex in the import of the VDAC precursor. The deletion of Sam50, the central component of the sorting and assembly machinery (SAM), led to both a strong defect in the assembly of VDAC and a reduction in the steady‐state level of VDAC. Metaxin 2‐depleted mitochondria had reduced levels of metaxin 1 and were deficient in import and assembly of VDAC and Tom40, but not of three matrix‐targeted precursors. We also observed a reduction in the levels of metaxin 1 and metaxin 2 in Sam50‐depleted mitochondria, implying a connection between these three proteins, although Sam50 and metaxins seemed to be in different complexes. We conclude that the pathway of VDAC biogenesis in human mitochondria involves the TOM complex, Sam50 and metaxins, and that it is evolutionarily conserved.
An accurate low-frequency model for the 3ω method
Authors: Battaglia J.-L. , Wiemer C. , Fanciulli M.
Published: May 2007

An analytical solution of the 3D heat diffusion problem, in the two-pad and four-pad 3ω experimental technique configurations, is achieved using integral transforms. It leads to rapid calculation of the average temperature on the heated area without any numerical problems whatever the dimensions of the narrow strip. Such an analytical resolution is of great interest in the low-frequency range, which is generally concerned by the method, where the finite thickness of the material plays a crucial role. In particular, we demonstrate that the 3D method is required to correctly calculate the heat diffusion along a narrow strip, when its length is particularly short, as it is the case in the two-pad configuration.
Diffusion in tight confinement: A lattice-gas cellular automaton approach. II. Transport properties
Authors: Demontis Pierfranco , Pazzona Federico G. , Suffritti Giuseppe B.
Published: May 2007

In this second paper the authors study the transport properties of the lattice-gas cellular automaton presented in Paper I [J. Chem. Phys. 126, 194709 (2007)] to model adsorption and dynamics of particles in a lattice of confining cells. Their work shows how a surprisingly simple parallel rule applied to a static network of cells joined by links set in space and time can generate a wide range of dynamical behaviors. In their model the cells are the elementary constituent objects of the network. They are a portion of space structured in sites which are energetically different. Each cell can accommodate a given maximum number of particles, and each pair of neighboring cells can exchange at most one particle at a time. The predictions of the model are in qualitative agreement with both experimental observations and molecular dynamics simulation results.