bluuebunny/crossref_metadata_2025_split huggingface dataset:
Van Allen Probe observations of periodic rising frequencies of the fast magnetosonic mode
Authors: Boardsen S. A. , Hospodarsky G. B. , Kletzing C. A. , Pfaff R. F. , Kurth W. S. , Wygant J. R. , MacDonald E. A. 
Published: November 2014

AbstractNear simultaneous periodic dispersive features of fast magnetosonic mode emissions are observed by both Van Allen Probes spacecraft while separated in magnetic local time by ~5 h: Probe A at 15 and Probe B at 9–11 h. Both spacecraft see similar frequency features, characterized by a periodic repetition at ~180 s. Each repetition is characterized by a rising frequency. Since no modulation is observed in the proton shell distribution, the plasma density, or in the background magnetic field at either spacecraft we conclude that these waves are not generated near the spacecraft but external to both spacecraft locations. Probe A while outside the plasmapause sees the start of each repetition ~40 s before probe B while deep inside the plasmasphere. We can qualitatively reproduce the dispersive features but not the quantitative details. The cause for this phenomena remains to be identified.
Waveforms of Langmuir turbulence in inhomogeneous solar wind plasmas
Authors: Krafft C. , Volokitin A. S. , Krasnoselskikh V. V. , de Wit T. Dudok 
Published: November 2014

AbstractModulated Langmuir waveforms have been observed by several spacecraft in various regions of the heliosphere, such as the solar wind, the electron foreshock, the magnetotail, or the auroral ionosphere. Many observations revealed the bursty nature of these waves, which appear to be highly modulated, localized, and clumped into spikes with peak amplitudes typically 3 orders of magnitude above the mean. The paper presents Langmuir waveforms calculated using a Hamiltonian model describing self‐consistently the resonant interaction of an electron beam with Langmuir wave packets in a plasma with random density fluctuations. These waveforms, obtained for different profiles of density fluctuations and ranges of parameters relevant to solar type III electron beams and plasmas measured at 1 AU, are presented in the form they would appear if recorded by a satellite moving in the solar wind. Comparison with recent measurements by the STEREO and WIND satellites shows that their characteristic features are very similar to the observations.
In situ observation of magnetic reconnection in the front of bursty bulk flow
Authors: Wang Rongsheng , Lu Quanming , Du Aimin , Nakamura Rumi , Lu San , Huang Can , Liu Chaoxu , Wu Mingyu 
Published: November 2014

AbstractUsing the Cluster observation in the magnetotail, we investigate the dynamic processes associated with a bursty bulk flow (BBF) event. The BBF is inferred to be caused by magnetic reconnection proceeding to the lobe region in its tail, called “primary reconnection.” On the BBF front, another reconnection was directly encountered by one of the four Cluster satellites, and no signatures of this reconnection were simultaneously measured by the satellite at the plasma sheet boundary. It indicates that this reconnection on the BBF front remained within the plasma sheet, called “secondary reconnection.” The secondary reconnection moved earthward and was followed by a magnetic island. A few earthward moving pulses of Bz were detected between the island and the primary reconnection site. These Bz pulses, propagating faster than the island ahead of it, would lead to a more compressed Bz magnetic field in the wake of the island. The observational scenario is in accordance to the model proposed to explain the generation of dipolarization front in simulations. Furthermore, both electrons and ions were significantly accelerated in this process. The mechanism is discussed also.
Characteristics of pitch angle distributions of hundreds of keV electrons in the slot region and inner radiation belt
Authors: Zhao H. , Li X. , Blake J. B. , Fennell J. F. , Claudepierre S. G. , Baker D. N. , Jaynes A. N. , Malaspina D. M. 
Published: November 2014

AbstractThe pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state‐of‐the‐art pitch angle‐resolved data from the Magnetic Electron Ion Spectrometer instrument onboard the Van Allen Probes, a detailed analysis of hundreds of keV electron PADs below L = 4 is performed, in which the PADs are categorized into three types: normal (flux peaking at 90°), cap (exceedingly peaking narrowly around 90°), and 90° minimum (lower flux at 90°) PADs. By examining the characteristics of the PADs of ∼460 keV electrons for over a year, we find that the 90° minimum PADs are generally present in the inner belt (L<2), while normal PADs dominate at L∼3.5–4. In the region between, 90° minimum PADs dominate during injection times and normal PADs dominate during quiet times. Cap PADs appear mostly at the decay phase of storms in the slot region and are likely caused by the pitch angle scattering of hiss waves. Fitting the normal PADs into sinnα form, the parameter n is much higher below L = 3 than that in the outer belt and relatively constant in the inner belt but changes significantly in the slot region (2 < L < 3) during injection times. As for the 90° minimum PADs, by performing a detailed case study, we find in the slot region this type of PAD is likely caused by chorus wave heating, but this mechanism can hardly explain the formation of 90° minimum PADs at the center of inner belt.
Ion composition in Titan's exosphere via the Cassini Plasma Spectrometer I: T40 encounter
Authors: Woodson A. K. , Smith H. T. , Crary F. J. , Johnson R. E. 
Published: November 2014

AbstractWe investigate the complex interaction between Saturn's magnetosphere and Titan's upper ionosphere using ion data acquired by the Cassini Plasma Spectrometer (CAPS) during the T40 encounter. Bounds on ion‐group abundances at altitudes between ~2733 and ~12,541 km are determined by fitting mass spectra with model functions derived from instrument calibration data. The spectra are dominated by H+, H2+, H3+, and two hydrocarbon groups with mass ranges 12–19 and 24–32 amu, respectively. Notably, this constitutes the first reported observation of H3+ in Titan's exosphere. These measurements are discussed in the context of data from the CAPS electron spectrometer (ELS) and the Ion and Neutral Mass Spectrometer (INMS), which fortuitously sampled the ionospheric outflow during the T40 encounter at altitudes between ~2225 and ~3034 km. The CAPS data reveal a composition that is constitutively similar to that sampled by INMS, with hydrocarbon ions first observed as far as ~11,000 km from Titan and increasing in density by more than an order of magnitude along Cassini's inbound trajectory. In addition, we juxtapose the CAPS ion data with numerical results from three different interaction models and show that it is consistent with the location of the field‐draping boundary described by Ulusen et al. (2012) and the Saturnward ion tail predicted by Sillanpää et al. (2006).
Field‐aligned currents in Saturn's southern nightside magnetosphere: Subcorotation and planetary period oscillation components
Authors: Hunt G. J. , Cowley S. W. H. , Provan G. , Bunce E. J. , Alexeev I. I. , Belenkaya E. S. , Kalegaev V. V. , Dougherty M. K. , Coates A. J. 
Published: November 2014

AbstractWe investigate magnetic data showing the presence of field‐aligned magnetosphere‐ionosphere coupling currents on 31 Cassini passes across Saturn's southern postmidnight auroral region. The currents are strongly modulated in magnitude, form, and position by the phase of the southern planetary period oscillations (PPOs). PPO‐independent currents are separated from PPO‐related currents using the antisymmetry of the latter with respect to PPO phase. PPO‐independent downward currents ~1.1 MA per radian of azimuth flow over the polar open field region indicative of significant plasma subcorotation are enhanced in an outer plasma sheet layer of elevated ionospheric conductivity carrying ~0.8 MA rad−1 and close principally in an upward directed current sheet at ~17°–19° ionospheric colatitude carrying ~2.3 MA rad−1 that maps to the outer hot plasma region in Saturn's magnetosphere (equatorial range ~11–16 Saturn radii (RS)) colocated with the UV oval. Subsidiary downward and upward currents ~0.5 MA rad−1 lie at ~19°–20.5° colatitude mapping to the inner hot plasma region, but no comparable currents are detected at larger colatitudes mapping to the cool plasma regime inside ~8 RS. PPO‐related currents at ~17.5°–20° colatitude overlap the main upward and subsidiary downward currents and carry comparable rotating upward and downward currents peaking at ~1.7 MA rad−1. The overall current layer colatitude is also modulated with 1° amplitude in the PPO cycle, maximum equatorward adjacent to the peak upward PPO current and maximum poleward adjacent to peak downward PPO current. This phasing requires the current system to be driven from the planetary atmosphere rather than directly from the magnetosphere.
Laboratory constraints on models of earthquake recurrence
Authors: Beeler N. M. , Tullis Terry , Junger Jenni , Kilgore Brian , Goldsby David 
Published: November 2014

AbstractIn this study, rock friction “stick‐slip” experiments are used to develop constraints on models of earthquake recurrence. Constant rate loading of bare rock surfaces in high‐quality experiments produces stick‐slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip‐rate‐dependent process that also determines the size of the stress drop and, as a consequence, stress drop varies weakly but systematically with loading rate. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low‐frequency earthquakes loaded by episodic slip. The experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a nonlinear slip predictable model. The fault's rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence covary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability, and successive stress drops are strongly correlated indicating a “memory” of prior slip history that extends over at least one recurrence cycle.
Multisensor observations of the Amazon‐Orinoco river plume interactions with hurricanes
Authors: Reul Nicolas , Quilfen Yves , Chapron Bertrand , Fournier Severine , Kudryavtsev Vladimir , Sabia Roberto 
Published: November 2014

AbstractAn analysis is presented for the spatial and intensity distributions of North Atlantic extreme atmospheric events crossing the buoyant Amazon‐Orinoco freshwater plume. The sea surface cooling amplitude in the wake of an ensemble of storm tracks traveling in that region is estimated from satellite products for the period 1998–2012. For the most intense storms, cooling is systematically reduced by ∼50% over the plume area compared to surroundings open‐ocean waters. Historical salinity and temperature observations from in situ profiles indicate that salt‐driven vertical stratification, enhanced oceanic heat content, and barrier‐layer presence within the plume waters are likely key oceanic factors to explain these results. Satellite SMOS surface salinity data combined with in situ observations are further used to detail the oceanic response to category 4 hurricane Igor in 2010. Argo and satellite measurements confirm the haline stratification impact on the cooling inhibition as the hurricane crossed the river plume. Over this region, the SSS mapping capability is further tested and demonstrated to monitor the horizontal distribution of the vertical stratification parameter. SMOS SSS data can thus be used to consistently anticipate the cooling inhibition in the wake of TCs traveling over the Amazon‐Orinoco plume region.
The role of morphology and wave‐current interaction at tidal inlets: An idealized modeling analysis
Authors: Olabarrieta Maitane , Geyer W. Rockwell , Kumar Nirnimesh 
Published: November 2014

AbstractThe outflowing currents from tidal inlets are influenced both by the morphology of the ebb‐tide shoal and interaction with incident surface gravity waves. Likewise, the propagation and breaking of incident waves are affected by the morphology and the strength and structure of the outflowing current. The 3‐D Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport (COAWST) modeling system is applied to numerically analyze the interaction between currents, waves, and bathymetry in idealized inlet configurations. The bathymetry is found to be a dominant controlling variable. In the absence of an ebb shoal and with weak wave forcing, a narrow outflow jet extends seaward with little lateral spreading. The presence of an ebb‐tide shoal produces significant pressure gradients in the region of the outflow, resulting in enhanced lateral spreading of the jet. Incident waves cause lateral spreading and limit the seaward extent of the jet, due both to conversion of wave momentum flux and enhanced bottom friction. The interaction between the vorticity of the outflow jet and the wave stokes drift is also an important driving force for the lateral spreading of the plume. For weak outflows, the outflow jet is actually enhanced by strong waves when there is a channel across the bar, due to the “return current” effect. For both strong and weak outflows, waves increase the alongshore transport in both directions from the inlet due to the wave‐induced setup over the ebb shoal. Wave breaking is more influenced by the topography of the ebb shoal than by wave‐current interaction, although strong outflows show intensified breaking at the head of the main channel.
Mixed layer salinity budget in the tropical Pacific Ocean estimated by a global GCM
Authors: Gao Shan , Qu Tangdong , Nie Xunwei 
Published: November 2014

AbstractThe mixed layer salinity (MLS) budget of the tropical Pacific is investigated using results from a model of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). The results focusing on the western Pacific freshwater pool indicate that the long‐term averaged surface freshwater flux is well balanced by ocean dynamics, in which the subsurface processes account for the major part. The MLS budget shows significant seasonal and interannual variability, as a consequence of interplay among surface freshwater flux, advection, mixing, and vertical entrainment. On seasonal time scale, both the MLS and mixed layer depth are largely controlled by surface freshwater flux. The opposite phase between the subsurface processes and the barrier layer thickness confirms the important influence of the barrier layer on vertical mixing and entrainment from below. On interannual time scale, all the MLS budget terms show significant ENSO signal, which in turn is highly correlated with the salinity front and barrier layer thickness in the equatorial Pacific.
Influence of local circulations on wind, moisture, and precipitation close to Manaus City, Amazon Region, Brazil
Authors: dos Santos Mercel J. , Silva Dias Maria A. F. , Freitas Edmilson D. 
Published: November 2014

AbstractThis paper presents long‐term‐derived local wind patterns as well as their role on moisture transport and on spatial/temporal distribution of precipitation close to Manaus City region. In this analysis we used surface weather station data and rainfall estimates from TRMM (Tropical Rainfall Measuring Mission) and CMORPH (Climate Prediction Center morphing method). The weather stations promoted information of wind direction and dew point temperature, used here as atmospheric moisture indicator. The 3‐hourly average of accumulated precipitation, calculated using satellite estimates (TRMM and CMORPH), allowed to assess the spatial distribution of the rainfall diurnal cycle and how it is modulated by the local circulations. The station data results show that in the daytime, between 9:00 and 18:00 local time, winds away from the rivers are frequent, indicating action of the river breeze. This wind condition transports moist air from the rivers to the Manaus City. Winds toward rivers are commonly observed at night and in the morning, mostly at Ponta Pelada airport station, and are evidence of the land breeze occurrence. These local winds transport drier air from Manaus City to the river regions, as verified at Ponta Pelada station. The evidence of the local circulations and their impact on the moisture transport are more obvious in the dry season. The rainfall diurnal cycle has a spatial tendency varying according to the hour of the day. In the afternoon and in the evening, maximum precipitation values are observed over land, whereas reduced rainfall values are verified over rivers. At dawn and in the morning, the maximum values of accumulated precipitation are found over the rivers, mainly over and around the Amazon River. This rainfall spatial distribution is very likely modulated by local circulations and is much more evident in the rainiest quarter (March–May).
The birth and death of transverse aeolian ridges on Mars
Authors: Geissler Paul E. 
Published: November 2014

AbstractTransverse aeolian ridges (TARs) are small bright windblown deposits found throughout the Martian tropics that stand a few meters tall and are spaced a few tens of meters apart. The origin of these features remains mysterious more than 20 years after their discovery on Mars. This paper presents a new hypothesis, that some of the TARs could be indurated dust deposits emplaced millions of years ago during periods of higher axial obliquity. It suggests that these TARs are primary depositional bed forms that accumulated in place from dust carried by the winds in suspension, perhaps in a manner comparable to antidunes on Earth, and were subsequently indurated and eroded to their current states by eons of sandblasting. It points out examples of modern dust drifts and dune‐like features that appear to have been recently formed by dust accumulating directly onto the surface from atmospheric suspension. It shows how these pristine dust deposits could evolve to explain the range of morphologies of the TARs. Finally, it explains how the known properties of many TARs are consistent with this hypothesis, including their composition, thermal behavior, and distribution.
Scaling of adult regional body mass and body composition as a whole to height: Relevance to body shape and body mass index
Authors: Schuna John M. , Peterson Courtney M. , Thomas Diana M. , Heo Moonseong , Hong Sangmo , Choi Woong , Heymsfield Steven B. 
Published: November 2014

ABSTRACTObjectivesAdult body mass (MB) empirically scales as height (Ht) squared (MB ∝ Ht2), but does regional body mass and body composition as a whole also scale as Ht2? This question is relevant to a wide range of biological topics, including interpretation of body mass index (BMI).MethodsDual‐energy X‐ray absorptiometry (DXA) was used to quantify regional body mass [head (MH), trunk, arms, and legs] and whole‐body composition [fat, lean soft tissue (LST), and bone mineral content (BMC)] in non‐Hispanic (NH) white, NH black, Mexican American, and Korean adults participating in the National Health and Nutrition Examination Survey (NHANES; n = 17,126) and Korean NHANES (n = 8,942). Regression models were developed to establish Ht scaling powers for each measured component with adjustments for age and adiposity.ResultsExploratory analyses revealed a consistent scaling pattern across men and women of the four population groups: regional mass powers, head (∼0.8–1) < arms and trunk (∼1.8–2.3) < legs (∼2.3–2.6); and body composition, LST (∼2.0–2.3) < BMC (∼2.1–2.4). Small sex and population differences in scaling powers were also observed. As body mass scaled uniformly across the eight sex and population groups as Ht∼2, tall and short subjects differed in body shape (e.g., MH/MB ∝ Ht−∼1) and composition.ConclusionsAdult human body shape and relative composition are a function of body size as represented by stature, a finding that reveals a previously unrecognized phenotypic heterogeneity as defined by BMI. These observations provide new pathways for exploring mechanisms governing the interrelations between adult stature, body morphology, biomechanics, and metabolism. Am. J. Hum. Biol., 27:372–379, 2015. © 2014 Wiley Periodicals, Inc.
Hormonal evidence of selection in utero revisited
Authors: Catalano R.A. , Currier R.J. , Steinsaltz D. 
Published: November 2014

ObjectivesHuman conception cohorts in gestation during stressful times reportedly yield lower ratios of male to female live births than do other conception cohorts. Much literature attributes this phenomenon to spontaneous abortion of less fit male fetuses. Controversy remains, however, as to whether stressful times make males fetuses less fit (“Shifting Distribution” of fitness) or whether male fetuses need greater fitness to avoid spontaneous abortion during stressful times (“Shifting Criterion” for survival).MethodsAlthough research using gestational hCG as a signal of fetal fitness reports support for the latter mechanism, we believe an analytic error casts doubt on those findings. Here we offered an alternative test that corrects the error.ConclusionThis more accurate test found similar results to those originally reported. Am. J. Hum. Biol. 27:426–431, 2015. © 2014 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
Retinal damage and vision loss in African American multiple sclerosis patients
Authors: Kimbrough Dorlan J. , Sotirchos Elias S. , Wilson James A. , Al‐Louzi Omar , Conger Amy , Conger Darrel , Frohman Teresa C. , Saidha Shiv , Green Ari J. , Frohman Elliot M. , Balcer Laura J. , Calabresi Peter A. 
Published: November 2014

ObjectiveTo determine whether African American (AA) multiple sclerosis (MS) patients exhibit more retinal damage and visual impairment compared to Caucasian American (CA) MS patients.MethodsA total of 687 MS patients (81 AAs) and 110 healthy control (HC) subjects (14 AAs) were recruited at 3 academic hospitals between 2008 and 2012. Using mixed effects regression models, we compared high‐ and low‐contrast visual acuity (HCVA and LCVA) and high‐definition spectral domain optical coherence tomography measures of retinal architecture between MS patients of self‐identified AA and CA ancestry.ResultsIn HCs, baseline peripapillary retinal nerve fiber layer (RNFL) thickness was 6.1µm greater in AAs (p = 0.047), whereas ganglion cell/inner plexiform layer (GCIP) thickness did not differ by race. In MS patients, baseline RNFL did not differ by race, and GCIP was 3.98µm thinner in AAs (p = 0.004). AAs had faster RNFL and GCIP thinning rates compared to CAs (p = 0.004 and p = 0.046, respectively). AA MS patients had lower baseline HCVA (p = 0.02) and worse LCVA per year of disease duration (p = 0.039). Among patients with an acute optic neuritis (AON) history, AAs had greater loss of HCVA than CA patients (p = 0.012).InterpretationThis multicenter investigation provides objective evidence that AA MS patients exhibit accelerated retinal damage compared to CA MS patients. Self‐identified AA ancestry is associated with worse MS‐related visual disability, particularly in the context of an AON history, suggesting a more aggressive inflammatory disease course among AA MS patients or a subpopulation therein. Ann Neurol 2015;77:228–236