bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument
Authors: Ergun R. E. , Morooka M. W. , Andersson L. A. , Fowler C. M. , Delory G. T. , Andrews D. J. , Eriksson A. I. , McEnulty T. , Jakosky B. M. 
Published: November 2015

AbstractWe present Mars' electron temperature (Te) and density (ne) altitude profiles derived from the MAVEN (Mars Atmosphere and Volatile EvolutioN) mission deep dip orbits in April 2015, as measured by the Langmuir probe instrument. These orbits had periapsides below 130 km in altitude at low solar zenith angles. The periapsides were above the peak in ne during this period. Using a Chapman function fit, we find that scale height and projected altitude of the ne peak are consistent with models and previous measurements. The peak electron density is slightly higher than earlier works. For the first time, we present in situ measurements of Te altitude profiles in Mars' dayside in the altitude range from ~130 km to 500 km and provide a functional fit. Importantly, Te rises rapidly with altitude from ~180 km to ~300 km. These results and functional fit are important for modeling Mars' ionosphere and understanding atmospheric escape.
Ultraviolet observations of the hydrogen coma of comet C/2013 A1 (Siding Spring) by MAVEN/IUVS
Authors: Crismani Matteo M. J. , Schneider Nicholas M. , Deighan Justin I. , Stewart A. Ian F. , Combi Michael , Chaffin Michael S. , Fougere Nicolas , Jain Sonal K. , Stiepen Arnaud , Yelle Roger V. , McClintock William E. , Clarke John T. , Holsclaw Gregory M. , Montmessin Frank , Jakosky Bruce M. 
Published: November 2015

AbstractWe used the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiting spacecraft to construct images of the hydrogen coma of comet C/2013 A1 (Siding Spring) days before its close encounter with Mars. We obtain a water production rate of 1.1 ± 0.5 × 1028 molecules/s and determine the total impacting fluence of atoms and molecules corresponding to the photodissociation of water and its daughter species to be 2.4 ± 1.2 × 104 kg. We use these observations to confirm predictions that the mass of delivered hydrogen is comparable to the existing reservoir above 150 km. Furthermore, we reconcile disparity between observations and predictions about the detectability of the hydrogen perturbation and thermospheric response.
A comparison of 3‐D model predictions of Mars' oxygen corona with early MAVEN IUVS observations
Authors: Lee Yuni , Combi Michael R. , Tenishev Valeriy , Bougher Stephen W. , Deighan Justin , Schneider Nicholas M. , McClintock William E. , Jakosky Bruce M. 
Published: November 2015

AbstractWe have compared our 3‐D hot O corona model predictions with the OI 130.4 nm emission detected by Imaging Ultraviolet Spectrograph/Mars Atmosphere and Volatile EvolutioN (IUVS/MAVEN) based completely on our best pre‐MAVEN understanding of the 3‐D structure of the thermosphere and ionosphere. The model was simulated appropriately for the observational conditions. In addition to dissociative recombination (DR) of O2+, DR of CO2+is also considered as an important hot O source. The model predictions showed excellent agreement with the transition altitude, the observed altitude variation of density, and the spatial variation of the corona with respect to the Mars‐Sun geometry. While previous models predicted escape rates covering a range of nearly 100, the brightness of the modeled hot O densities is a factor of ~1.5 lower than the observations. We discuss possible changes to the model that could come from further analysis of MAVEN measurements and that might close the gap between the modeled and observed brightness.
The spatial distribution of planetary ion fluxes near Mars observed by MAVEN
Authors: Brain D. A. , McFadden J. P. , Halekas J. S. , Connerney J. E. P. , Bougher S. W. , Curry S. , Dong C. F. , Dong Y. , Eparvier F. , Fang X. , Fortier K. , Hara T. , Harada Y. , Jakosky B. M. , Lillis R. J. , Livi R. , Luhmann J. G. , Ma Y. , Modolo R. , Seki K. 
Published: November 2015

AbstractWe present the results of an initial effort to statistically map the fluxes of planetary ions on a closed surface around Mars. Choosing a spherical shell ~1000 km above the planet, we map both outgoing and incoming ion fluxes (with energies >25 eV) over a 4 month period. The results show net escape of planetary ions behind Mars and strong fluxes of escaping ions from the northern hemisphere with respect to the solar wind convection electric field. Planetary ions also travel toward the planet, and return fluxes are particularly strong in the southern electric field hemisphere. We obtain a lower bound estimate for planetary ion escape of ~3 × 1024 s−1, accounting for the ~10% of ions that return toward the planet and assuming that the ~70% of the surface covered so far is representative of the regions not yet visited by Mars Atmosphere and Volatile EvolutioN (MAVEN).
Probing the Martian atmosphere with MAVEN/IUVS stellar occultations
Authors: Gröller H. , Yelle R. V. , Koskinen T. T. , Montmessin F. , Lacombe G. , Schneider N. M. , Deighan J. , Stewart A. I. F. , Jain S. K. , Chaffin M. S. , Crismani M. M. J. , Stiepen A. , Lefèvre F. , McClintock W. E. , Clarke J. T. , Holsclaw G. M. , Mahaffy P. R. , Bougher S. W. , Jakosky B. M. 
Published: November 2015

AbstractThe first campaign of stellar occultations with the Imaging Ultraviolet Spectrograph (IUVS) instrument on board of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission was executed between 24 and 26 March 2015. From this campaign 13 occultations are used to retrieve CO2 and O2 number densities in the altitude range between 100 and 150 km. Observations probe primarily the low‐latitude regions on the nightside of the planet, just past the dawn and dusk terminator. Calculation of temperature from the CO2 density profiles reveals that the lower thermosphere is significantly cooler than predicted by the models in the Mars Climate Database. A systematically cold layer with temperatures of 105–120 K is seen in the occultations at a pressure level around 7 × 10−6 Pa.
High‐altitude gravity waves in the Martian thermosphere observed by MAVEN/NGIMS and modeled by a gravity wave scheme
Authors: Yiğit Erdal , England Scott L. , Liu Guiping , Medvedev Alexander S. , Mahaffy Paul R. , Kuroda Takeshi , Jakosky Bruce M. 
Published: November 2015

AbstractFirst high‐altitude observations of gravity wave (GW)‐induced CO2 density perturbations in the Martian thermosphere retrieved from NASA's Neutral Gas Ion Mass Spectrometer (NGIMS) instrument on board the Mars Atmosphere Volatile EvolutioN (MAVEN) satellite are presented and interpreted using the extended GW parameterization of Yiğit et al. (2008) and the Mars Climate Database as an input. Observed relative density perturbations between 180 and 220 km of 20–40% demonstrate appreciable local time, latitude, and altitude variations. Modeling for the spatiotemporal conditions of the MAVEN observations suggests that GWs can directly propagate from the lower atmosphere to the thermosphere, produce appreciable dynamical effects, and likely contribute to the observed fluctuations. Modeled effects are somewhat smaller than the observed, but their highly variable nature is in qualitative agreement with observations. Possible reasons for discrepancies between modeling and measurements are discussed.
MAVEN and the Mars Initial Reference Ionosphere model
Authors: Mendillo Michael , Narvaez Clara , Matta Majd , Vogt Marissa , Mahaffy Paul , Benna Mehdi , Jakosky Bruce 
Published: November 2015

AbstractThe Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite measured the distribution of thermal ions (2–150 amu) at ionospheric heights (~130–400 km) under midday conditions during the “Deep‐Dip” orbit campaign from 17 to 22 April 2015. Assuming charge neutrality, we use the sum of NGIMS ions as a proxy for electron density (Ne) and compare results with a new version of the Mars Initial Reference Ionosphere (MIRI) developed for this study. At altitudes where the transition between photochemical and dynamical processes occurs (130–200 km), the NGIMS results agree with the shape of the MIRI‐predicted Ne(h) profiles, but the model predictions are a factor of 2 higher. Above 200 km, the NGIMS gradients of total ions versus height diverge even more from MIRI's Ne(h) predictions for reasons that may involve crustal‐B field effects, ionopause‐like boundaries, and horizontal plasma transport away from the noon sector—factors not yet included in MIRI.
Response of the intertropical convergence zone to zonally asymmetric subtropical surface forcings
Authors: Shaw Tiffany A. , Voigt Aiko , Kang Sarah M. , Seo Jeongbin 
Published: November 2015

AbstractThe energetic framework predicts no shift of the zonal mean Intertropical Convergence Zone (ITCZ) in response to zonally asymmetric forcings (zonal warming and cooling regions with zero zonal mean) assuming radiative feedbacks are linear. Here we show the ITCZ shifts southward in response to a zonally asymmetric forcing in the Northern Hemisphere subtropics in a slab ocean aquaplanet model. The southward shift is consistent with decreased zonal mean energy input to the atmosphere due to cloud radiative effect changes in the cooling region. When cloud‐radiative feedbacks are disabled the ITCZ shifts northward consistent with changes in the warming region where increased energy input via surface heat fluxes and stationary Rossby‐wave transport dominate. Competition between cooling and warming regions leads to changes in gross moist stability. Our results show rectification of zonally asymmetric forcings play an important role in zonal mean ITCZ dynamics and highlight the importance of assessing the momentum budget when interpreting ITCZ shifts.
Neutral density response to solar flares at Mars
Authors: Thiemann E. M. B. , Eparvier F. G. , Andersson L. A. , Fowler C. M. , Peterson W. K. , Mahaffy P. R. , England S. L. , Larson D. E. , Lo D. Y. , Schneider N. M. , Deighan J. I. , McClintock W. E. , Jakosky B. M. 
Published: November 2015

AbstractFirst direct observations of heating of the Mars neutral atmosphere by solar flares are presented in this study. Solar flares were detected using the Extreme Ultraviolet Monitor on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, and upper atmospheric temperature enhancements were determined by changes in the density scale height of Argon (Ar) made by the Neutral Gas and Ion Mass Spectrometer also on board MAVEN. We analyzed 14 M‐class or greater flares that occurred during the early part of the MAVEN mission in addition to a 30 day period of high flare activity during May 2015. We report that the Mars dayside upper atmosphere shows significant heating near the flare soft X‐ray peak; and it responds and recovers rapidly to heating from M‐class or larger flares. In addition, we present atmospheric density versus altitude profiles that were taken near the soft X‐ray peak of two flares.
On the utility of in situ soil moisture observations for flash drought early warning in Oklahoma, USA
Authors: Ford Trent W. , McRoberts D. Brent , Quiring Steven M. , Hall Ryann E. 
Published: November 2015

AbstractDrought early warning systems are a vital component of drought monitoring and require information at submonthly time scales because of the rapidly evolving nature of drought. This study evaluates the utility of in situ soil moisture observations for drought early warning in Oklahoma. Soil moisture was used to identify drought events, and the results were compared with the U.S. Drought Monitor with respect to the identification of drought onset. Soil moisture observations consistently identify rapid‐onset (flash) drought events earlier than the U.S. Drought Monitor. Our results show that soil moisture percentiles provide a 2–3 week lead time over the U.S. Drought Monitor based on five flash drought events that occurred in Oklahoma between 2000 and 2013. We conclude that in situ soil moisture observations are an important source of information for early warning of flash drought events in the Oklahoma.
Deriving plasma densities in tenuous plasma regions, with the spacecraft potential under active control
Authors: Andriopoulou M. , Nakamura R. , Torkar K. , Baumjohann W. , Hoelzl B. 
Published: November 2015

AbstractVariations of the floating potential on spacecraft are often used to derive plasma densities, complementing the plasma instrument measurements. All spacecraft of the Cluster mission are equipped with Active Spacecraft POtential Control (ASPOC) instruments that control the spacecraft potential. Although the ASPOC operation increases the accuracy of electric field and plasma measurements, it prevents a direct use of the spacecraft potential variations to derive plasma densities. In this work we develop a new reconstruction method of uncontrolled spacecraft potential from controlled spacecraft potential data and a derived photoelectron curve, using multispacecraft observations. We assume that the same curve governs the plasma environment for the spacecraft with ASPOC on and off. The current work focuses on reconstructions in the magnetotail region. The period that was more extensively studied was the one from August to October 2003, when the spacecraft were close to each other, while results from the periods of August–October 2001, 2002, and 2004, when the Cluster spacecraft had their apogee in the magnetotail region, are also presented. In this way, we investigate how the photoelectron curve varies at different time intervals and also how the reconstruction results are modified when the distance between the spacecraft is increasing. Finally, by using the reconstructed results, we proceed by estimating the plasma densities and we discuss the uncertainties of such estimations. While, on average, spacecraft potential measurements are successfully reconstructed, plasma and solar activity variations on short timescales seem to affect the reconstructions, requiring in some cases more detailed analysis in order to achieve results with higher accuracy. Moreover, there are some limitations while deriving results in very tenuous plasma regions due to increased uncertainties in some of the scientific measurements used there. The results and the methods developed for this work can be applied for any other current and future mission with instruments that control the spacecraft potential, such as the recently launched Magnetospheric Multiscale Mission.
Tectonic deformation in the Tyrrhenian: A novel statistical approach to infer the role of the Calabrian Arc complex
Authors: Splendore Raffaele , Marotta Anna Maria , Barzaghi Riccardo 
Published: November 2015

AbstractA thermomechanical model is used to analyze the strain pattern due to the Africa‐Eurasia convergence in the area that extends from the Calabrian Arc to the Alpine domain and the role that is played by the Calabrian Arc complex in controlling the northward propagation of the tectonic stress. After a preliminary analysis to eliminate GPS stations that are not representative of the main regional tectonic process, the predicted deformation is compared to that based on GPS observations by using a novel χ2 test in which both data and model uncertainties are taken into account. A large amount of the tectonic force (at least 75%) that is associated with the Africa‐Eurasia convergence is accommodated by the Calabrian Arc complex, which plays a crucial role in controlling the intraplate propagation of the stress in the south Tyrrhenian area. Furthermore, a strong lithosphere, which is characterized by a granite‐type upper crust, diabase‐type lower crust, and peridotite‐type lithosphere mantle, must pave the south Tyrrhenian; and a soft lithosphere, which is characterized by a granite‐type upper crust, granulite‐type lower crust, and peridotite‐type lithospheric mantle, must pave the surrounding area to reproduce the expected regional compression in the SE‐NW direction and extension in the perpendicular direction. Finally, the local deformation at high latitudes is not sensitive to variations in the boundary conditions along a limited portion of the Calabrian Arc.
Sensitivity of diurnal variation in simulated precipitation during East Asian summer monsoon to cumulus parameterization schemes
Authors: Choi In‐Jin , Jin Emilia Kyung , Han Ji‐Young , Kim So‐Young , Kwon Young 
Published: November 2015

AbstractThe capability to simulate the diurnal variation of precipitation over East Asia region during the summertime of 2011 is investigated using five different cumulus parameterization schemes with the Weather Research and Forecasting model. A semidiurnal cycle with a 12 h interval over land and a diurnal cycle with a 24 h interval over ocean are commonly found in all simulations, consistent with the observed diurnal cycle. Two observed dominant peaks in the early morning and afternoon are reproduced in all simulations. With overestimated precipitation rate, however, the simulated afternoon peaks occur earlier than the observed peaks by 2 h for the Kain‐Fritsch (KF) and Simplified Arakawa‐Schubert schemes, and by 3 h for the Betts‐Miller‐Janjić and Tiedtke schemes. The overestimation of simulated precipitation frequency leads to amplitude and phase errors in the precipitation rate, and the early peak time of simulated precipitation intensity intensifies the phase error in the simulation over land. The KF scheme with alternative trigger function (KFtr) based on moisture advection provides slightly better results in terms of alleviating the overestimated precipitation rate and frequency and delaying the afternoon peaks. Additional sensitivity simulations based on the change of temperature perturbation in the trigger function of the KF and KFtr schemes demonstrate the afternoon peak tends to be delayed as temperature perturbation decreases, implying the significant role of convective initiation frequency in determining diurnal peaks of precipitation. Modulation of temperature perturbation alleviates the precipitation frequency bias, while it could not resolve the precipitation intensity bias.
Pixel‐scale assessment and uncertainty analysis of AIRS and MODIS ice cloud optical thickness and effective radius
Authors: Kahn B. H. , Schreier M. M. , Yue Q. , Fetzer E. J. , Irion F. W. , Platnick S. , Wang C. , Nasiri S. L. , L'Ecuyer T. S. 
Published: November 2015

AbstractComparisons of collocated Atmospheric Infrared Sounder (AIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS) ice cloud optical thickness (τ) and effective radius (re) retrievals and their uncertainty estimates are described at the pixel scale. While an estimated 27% of all AIRS fields of view contain ice cloud, only 7% contain spatially uniform ice according to the MODIS 1 km optical property phase mask. The ice cloud comparisons are partitioned by horizontal variability in cloud amount, cloud top thermodynamic phase, vertical layering of clouds, and other parameters. The magnitudes of τ and re and their relative uncertainties are compared for a wide variety of pixel‐scale cloud complexity. The correlations of τ and re between the two instruments are strong functions of horizontal cloud heterogeneity and vertical cloud structure, with the highest correlations found in single‐layer, horizontally homogeneous clouds over the low‐latitude tropical oceans. While the τ comparisons are essentially unbiased for homogeneous ice cloud with variability that depends on scene complexity, a bias of 5–10 µm remains in re within the most homogeneous scenes identified, consistent with known radiative transfer differences in the visible and infrared bands. The AIRS and MODIS uncertainty estimates reflect the wide variety of cloud complexity, with greater magnitudes in scenes with larger horizontal variability. The AIRS averaging kernels suggest scene‐dependent information content that is consistent with infrared sensitivity to ice clouds. The AIRS‐normalized χ2 radiance fits suggest that accounting for horizontal cloud variability is likely to improve the AIRS ice cloud retrievals.
Introduction to special issue on “Long‐term changes and trends in the stratosphere, mesosphere, thermosphere and ionosphere”
Authors: Cnossen Ingrid , Laštovička Jan , Emmert John T. 
Published: November 2015

AbstractThis special issue bundles some of the latest results on decadal‐scale variations in the stratosphere, mesosphere, thermosphere, and ionosphere, following on from the 8th Workshop on Long‐Term Changes and Trends in the Atmosphere, held in Cambridge, UK, on 28–31 July 2014. Emmert et al. () provided a short report of the workshop. This introduction briefly describes the relevance of the field and highlights some of the recent progress that has been made.
Analysis of pressure‐strain and pressure gradient‐scalar covariances in cloud‐topped boundary layers: A large‐eddy simulation study
Authors: Heinze Rieke , Mironov Dmitrii , Raasch Siegfried 
Published: November 2015

AbstractA detailed analysis of the pressure‐scrambling terms (i.e., the pressure‐strain and pressure gradient‐scalar covariances) in the Reynolds‐stress and scalar‐flux budgets for cloud‐topped boundary layers (CTBLs) is performed using high‐resolution large‐eddy simulation (LES). Two CTBLs are simulated — one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure‐scrambling terms are decomposed into contributions due to turbulence‐turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two‐component‐limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure‐scrambling terms shows that the turbulence‐turbulence and buoyancy contributions are most significant for cloud‐topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading‐order contribution near the surface. A comparison of models of the pressure‐scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure‐scrambling terms reasonably well. It can be applied in the second‐order turbulence modeling of cloud‐topped boundary layer flows, provided some uncertainties are tolerated.
Return to the Taung cave paradigm
Authors: McKee Jeffrey K. 
Published: November 2015

ABSTRACTObjectivesThe Taung hominin fossil was recovered in 1924 during quarry operations in the tufa formations of the Buxton Limeworks. Reconstructions of the depositional environment of the juvenile Australopithecus skull have concentrated on the types of caves that form within the tufa. Hopley et al. (Am J Phys Anthropol 151 (2013) 316–324) proposed a new model in which the pink carbonate deposits, in which many of the Taung fossils are found, formed as open terrestrial pedogenic deposits. The objective here is to challenge that notion.Materials and MethodsObservations of the depositional environments at Taung are based upon the University of the Witwatersrand paleontological excavations at the Buxton Limeworks from 1988 to 1993, and subsequent laboratory analysis of the fossils and sediments.ResultsHopley et al. (Am J Phys Anthropol 151 (2013) 316–324) conflate numerous distinct outcroppings of the pink carbonates as a single “unit.” The excavations revealed numerous fossiliferous deposits that differ greatly in taphonomic origins and formation processes, and that cannot be considered a “unit” despite the commonality of pink carbonates. There are deposits that fit the model proposed by Hopley et al. (Am J Phys Anthropol 151 (2013) 316–324), but they are not the ones that yielded the most significant fossils.DiscussionMost of the fossiliferous deposits, including those most likely to have yielded the Taung hominin, are best reconstructed as being of karst origins. Am J Phys Anthropol 159:348–351, 2016. © 2015 Wiley Periodicals, Inc.