bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of unrest at Laguna del Maule volcanic field (Chile) from InSAR and GPS measurements, 2003 to 2014
Authors: Le Mével Hélène , Feigl Kurt L. , Córdova Loreto , DeMets Charles , Lundgren Paul 
Published: July 2015

AbstractThe Laguna del Maule (LdM) volcanic field in the southern volcanic zone of the Chilean Andes exhibits a large volume of rhyolitic material erupted during postglacial times (20–2 ka). Since 2007, LdM has experienced an unrest episode characterized by high rates of deformation. Analysis of new GPS and Interferometric Synthetic Aperture Radar (InSAR) data reveals uplift rates greater than 190 mm/yr between January 2013 and November 2014. The geodetic data are modeled as an inflating sill at depth. The results are used to calculate the temporal evolution of the vertical displacement. The best time function for modeling the InSAR data set is a double exponential model with rates increasing from 2007 through 2010 and decreasing slowly since 2010. We hypothesize that magma intruding into an existing silicic magma reservoir is driving the surface deformation. Modeling historical uplift at Yellowstone, Long Valley, and Three Sisters volcanic fields suggests a common temporal evolution of vertical displacement rates.
Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18–19 January 2013
Authors: Blum L. W. , Halford A. , Millan R. , Bonnell J. W. , Goldstein J. , Usanova M. , Engebretson M. , Ohnsted M. , Reeves G. , Singer H. , Clilverd M. , Li X. 
Published: July 2015

AbstractElectromagnetic ion cyclotron (EMIC) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of EMIC wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at the end of 18 January and again late on 19 January, concurrent with particle injections, substorm activity, and enhanced magnetospheric convection. The structure, timing, and spatial extent of the waves are compared to those of the precipitation during both days to determine when and where EMIC waves cause radiation belt electron precipitation. The conjugate measurements presented here provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss.
Time‐varying ionosonde trend: Case study of Sodankylä hmF2 data 1957–2014
Authors: Roininen Lassi , Laine Marko , Ulich Thomas 
Published: July 2015

AbstractWe discuss trend analysis of nonstationary ionosonde hmF2 time series measured at Sodankylä Geophysical Observatory (67.4∘N, 26.7∘E), Finland, 1957–2014. We model the hmF2 with a dynamic regression time series model with the following components: a slowly varying background level, seasonal variations, and solar effects. We analyze the time series with a dynamic linear state space model. Such an approach allows model components to vary in time, allowing us to study the dynamic stochastic nature of the underlying long‐term trend. This feature is lacking in most time series models used in atmospheric and environmental long‐term trend analyses. Our objective is to understand the long‐term hmF2 trend with respect to increased levels of carbon dioxide and methane in the atmosphere. Based on model estimates, this phenomenon is predicted to cool the thermosphere and leads to decrease of the altitude of the so‐called F2 layer peak. After accounting for the effects of solar activity variations on the data, we see that the estimated trend shows an almost 30 km decrease of the F2 layer peak during the observation period. The decrease of the peak during 1990–2010 is significantly greater than during earlier observation period.
Improving solar wind modeling at Mercury: Incorporating transient solar phenomena into the WSA‐ENLIL model with the Cone extension
Authors: Dewey Ryan M. , Baker Daniel N. , Anderson Brian J. , Benna Mehdi , Johnson Catherine L. , Korth Haje , Gershman Daniel J. , Ho George C. , McClintock William E. , Odstrcil Dusan , Philpott Lydia C. , Raines Jim M. , Schriver David , Slavin James A. , Solomon Sean C. , Winslow Reka M. , Zurbuchen Thomas H. 
Published: July 2015

AbstractCoronal mass ejections (CMEs) and other transient solar phenomena play important roles in magnetospheric and exospheric dynamics. Although a planet may interact only occasionally with the interplanetary consequences of these events, such transient phenomena can result in departures from the background solar wind that often involve more than an order of magnitude greater ram pressure and interplanetary electric field applied to the planetary magnetosphere. For Mercury, an order of magnitude greater ram pressure combined with high Alfvén speeds and reconnection rates can push the magnetopause essentially to the planet's surface, exposing the surface directly to the solar wind flow. In order to understand how the solar wind interacts with Mercury's magnetosphere and exosphere, previous studies have used the Wang‐Sheeley‐Arge (WSA)‐ENLIL solar wind modeling tool to calculate basic and composite solar wind parameters at Mercury's orbital location. This model forecasts only the background solar wind, however, and does not include major transient events. The Cone extension permits the inclusion of CMEs and related solar wind perturbations and thus enables characterization of the effects of strong solar wind disturbances on the Mercury system. The Cone extension is predicated on the assumption of constant angular and radial velocities of CMEs to integrate these phenomena into the WSA‐ENLIL coupled model. Comparisons of the model results with observations by the MESSENGER spacecraft indicate that the WSA‐ENLIL+Cone model more accurately forecasts total solar wind conditions at Mercury and has greater predictive power for magnetospheric and exospheric processes than the WSA‐ENLIL model alone.
Latitudinal dependence of short timescale fluctuations during intense geomagnetic storms: A permutation entropy approach
Authors: De Michelis Paola , Consolini Giuseppe , Tozzi Roberta 
Published: July 2015

AbstractThe present study is focused on the analysis of the latitudinal dependence of complexity degree of the short timescale geomagnetic field fluctuations during four intense geomagnetic storms occurring between 2000 and 2003. The aim is that of investigating the qualitative and quantitative changes in the dynamical properties of the magnetospheric system during magnetically disturbed periods. We analyze the short timescale fluctuations (<120 min) of the horizontal component of the Earth's magnetic field at nine different geomagnetic observatories from 49°N magnetic latitude (MLat) to 87°N MLat, by filtering the signal via empirical mode decomposition and successively by applying the permutation entropy analysis to the filtered time series. We show that some properties of the geomagnetic fluctuations during the selected periods are the result of dynamical changes in the magnetospheric system response to the solar wind changes and that these geomagnetic fluctuations display a complex character during the geomagnetic storm development. This evidence supports the idea that the geomagnetic storm nature may be the result of a cooperative and collective dynamics. We also find that the permutation entropy values change with latitude suggesting a latitudinal dependence of the complexity degree of the signals.
Crustal deformation in the New Madrid seismic zone and the role of postseismic processes
Authors: Boyd Oliver S. , Smalley Robert , Zeng Yuehua 
Published: July 2015

AbstractGlobal Navigation Satellite System data across the New Madrid seismic zone (NMSZ) in the central United States over the period from 2000 through 2014 are analyzed and modeled with several deformation mechanisms including the following: (1) creep on subsurface dislocations, (2) postseismic frictional afterslip and viscoelastic relaxation from the 1811–1812 and 1450 earthquakes in the NMSZ, and (3) regional strain. In agreement with previous studies, a dislocation creeping at about 4 mm/yr between 12 and 20 km depth along the downdip extension of the Reelfoot fault reproduces the observations well. We find that a dynamic model of postseismic frictional afterslip from the 1450 and February 1812 Reelfoot fault events can explain this creep. Kinematic and dynamic models involving the Cottonwood Grove fault provide minimal predictive power. This is likely due to the smaller size of the December 1811 event on the Cottonwood Grove fault and a distribution of stations better suited to constrain localized strain across the Reelfoot fault. Regional compressive strain across the NMSZ is found to be less than 3 × 10−9/yr. If much of the present‐day surface deformation results from afterslip, it is likely that many of the earthquakes we see today in the NMSZ are aftershocks from the 1811–1812 New Madrid earthquakes. Despite this conclusion, our results are consistent with observations and models of intraplate earthquake clustering. Given this and the recent paleoseismic history of the region, we suggest that seismic hazard is likely to remain significant.
Effects of healing on the seismogenic potential of carbonate fault rocks: Experiments on samples from the Longmenshan Fault, Sichuan, China
Authors: Chen Jianye , Verberne Berend A. , Spiers Christopher J. 
Published: July 2015

AbstractFault slip and healing history may crucially affect the fault seismogenic potential in the earthquake nucleation regime. Here we report direct shear friction tests on simulated gouges derived from a carbonate fault breccia, and from a clay/carbonate fault‐core gouge, retrieved from a surface exposure of the Longmenshan Fault Zone (LFZ) which hosted the 2008 Wenchuan earthquake. The experiments were conducted under dry and hydrothermal conditions, at temperatures up to 140°C, at an effective normal stress of 50 MPa, and involved sequential velocity‐stepping (VS), slide‐hold‐slide (SHS), and velocity‐stepping stages. Dry tests performed on breccia‐derived samples showed no dependence of (quasi) steady state friction (μss) on SHS or VS history, and a log linear relation between transient peak healing (Δμpk) and hold time, or classical “Dieterich‐type” healing behavior. By contrast, all experiments conducted under hydrothermal conditions were characterized by “non‐Dieterich” healing behavior. This included (1) an increase in μss upon resliding after a hold period and (2) an increase in friction rate parameter (a − b), after SHS testing. Comparison with previous results suggests that the healing behavior seen in our wet tests may be attributed to solution transfer processes occurring during hold periods. Our findings imply that the shallow portions of faults with carbonate/clay‐rich cores (e.g., the LFZ) can heal much faster than previously recognized, while the upper limit of the seismogenic zone may migrate to deeper levels during interseismic periods. These effects have important implications for understanding the seismic cycle in tectonically active carbonate terrains.
Resolution analysis by random probing
Authors: Fichtner Andreas , Leeuwen Tristan van 
Published: July 2015

AbstractWe develop and apply methods for resolution analysis in tomography, based on stochastic probing of the Hessian or resolution operators. Key properties of our methods are (i) low algorithmic complexity and easy implementation, (ii) applicability to any tomographic technique, including full‐waveform inversion and linearized ray tomography, (iii) applicability in any spatial dimension and to inversions with a large number of model parameters, (iv) low computational costs that are mostly a fraction of those required for synthetic recovery tests, and (v) the ability to quantify both spatial resolution and interparameter trade‐offs. Using synthetic full‐waveform inversions as benchmarks, we demonstrate that autocorrelations of random‐model applications to the Hessian yield various resolution measures, including direction‐ and position‐dependent resolution lengths and the strength of interparameter mappings. We observe that the required number of random test models is around five in one, two, and three dimensions. This means that the proposed resolution analyses are not only more meaningful than recovery tests but also computationally less expensive. We demonstrate the applicability of our method in a 3‐D real‐data full‐waveform inversion for the western Mediterranean. In addition to tomographic problems, resolution analysis by random probing may be used in other inverse methods that constrain continuously distributed properties, including electromagnetic and potential‐field inversions, as well as recently emerging geodynamic data assimilation.
Realizing a terrestrial reference frame using the Global Positioning System
Authors: Haines Bruce J. , Bar‐Sever Yoaz E. , Bertiger Willy I. , Desai Shailen D. , Harvey Nate , Sibois Aurore E. , Weiss Jan P. 
Published: July 2015

AbstractWe describe a terrestrial reference frame (TRF) realization based on Global Positioning System (GPS) data alone. Our approach rests on a highly dynamic, long‐arc (9 day) estimation strategy and on GPS satellite antenna calibrations derived from Gravity Recovery and Climate Experiment and TOPEX/Poseidon low Earth orbit receiver GPS data. Based on nearly 17 years of data (1997–2013), our solution for scale rate agrees with International Terrestrial Reference Frame (ITRF)2008 to 0.03 ppb yr−1, and our solution for 3‐D origin rate agrees with ITRF2008 to 0.4 mm yr−1. Absolute scale differs by 1.1 ppb (7 mm at the Earth's surface) and 3‐D origin by 8 mm. These differences lie within estimated error levels for the contemporary TRF.
Plankton dynamics in a cyclonic eddy in the Southern California Current System
Authors: Chenillat Fanny , Franks Peter J. S. , Rivière Pascal , Capet Xavier , Grima Nicolas , Blanke Bruno 
Published: July 2015

AbstractThe California Current System is an eastern boundary upwelling system (EBUS) with high biological production along the coast. Oligotrophic offshore waters create cross‐shore gradients of biological and physical properties, which are affected by intense mesoscale eddy activity. The influence of eddies on ecosystem dynamics in EBUS is still in debate. To elucidate the mechanisms that influence the dynamics of ecosystems trapped in eddies, and the relative contribution of horizontal and vertical advection in determining local production, we analyze a particular cyclonic eddy using Lagrangian particle‐tracking analyses of numerical Eulerian. The eddy formed in a coastal upwelling system; coastal waters trapped in the eddy enabled it to leave the upwelling region with high concentrations of plankton and nutrients. The ecosystem was initially driven mainly by recycling of biological material. As the eddy moved offshore, production in its core was enhanced compared to eddy exterior waters through Ekman pumping of nitrate from below the euphotic zone; this Ekman pumping was particularly effective due to the shallow nitracline in the eddy compared to eddy exterior waters. Both eddy trapping and Ekman pumping helped to isolate and maintain the ecosystem productivity in the eddy core. This study shows the importance of cyclonic eddies for biological production in EBUS: they contribute both to the redistribution of the coastal upwelling ecosystem and are local regions of enhanced new production. Together, these processes impact cross‐shore gradients of important biological properties.
Temporal and radiometric statistics on lightning flashes observed from space with the ISUAL spectrophotometer
Authors: Offroy Marc , Farges Thomas , Kuo Cheng Ling , Chen Alfred Bing‐Chih , Hsu Rue‐Ron , Su Han‐Tzong , Takahashi Yukihiro , Mende Stephen B. , Frey Harald U. 
Published: July 2015

AbstractThe Imager of Sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT‐2 satellite was launched in 2004 and records transient luminous events (TLEs). ISUAL is an instrument composed of an imager and a multichannel spectrophotometer which is able to measure the brightness from far ultraviolet to near infrared for TLEs and lightning flashes. Several types of TLEs have been identified, classified, and documented between 2004 and 2014. However, no statistical analyses on lightning have already been realized. In this paper, we focus on lightning flashes which did not induce TLEs. Statistics about brightness or temporal dynamic are presented from fitted waveforms from far ultraviolet to near infrared, after having corrected for atmospheric effects for each spectrophotometer channels. We demonstrate that the lightning/satellite distance and the altitude of the lightning need to be taken into account. The lightning waveforms from each spectrophotometer channel could be modeled as an exponential pulsed function which the shape could be explained by the photon propagation in the cloud. The median values at 777.4 nm are 1.63 × 10−6 W m−2 for the maximum brightness, 5.85 × 104 J for the total energy at the source, 414 µs for the full width half maximum, 620 µs for the full width at quarter of maximum, and 170 µs for the risetime. Results are compared with previous experiments performed from visible to near‐infrared domains. The median temporal variables for near‐infrared waveforms are shorter than the values of the UV waveforms.
A Thermodynamic, kinematic and microphysical analysis of a jet and gigantic jet‐producing Florida thunderstorm
Authors: Lazarus S. M. , Splitt M. E. , Brownlee James , Spiva Nicholas , Liu Ningyu 
Published: July 2015

AbstractThis paper presents a meteorological analysis of a storm that produced two jets, four gigantic jets (GJ), and a starter, which were observed by two radars as well as the Kennedy Space Center 4‐Dimensional Lightning Surveillance System on 3 August 2013 in Central Florida. The work is the first application of dual polarization data to a jet‐producing storm and is the fifth case related to a tropical disturbance. The storm environment is consistent with the moist tropical paradigm that characterizes about three quarters of the surface and aircraft observed jet and GJ events. The most unstable (MU) convective available potential energy is not unusual for Florida summer convection and is below the climatological mean for these events. An unusual speed shear layer is located near the storm equilibrium level (EL) and the storm exhibits a tilted structure with CGs displaced upshear. The turbulence, as measured by the eddy dissipation rate, is extreme near the storm top during the event window, consistent with the GJ mixing hypothesis. The individual events are collocated with, and track along, the center axis of the divergent outflow at the EL and occur within the region of the coldest GOES IR temperatures—placing the events within the overshoot. The dual polarization data indicate a deep graupel column, extending above the mixed phase layer, to a 13 km altitude.
Modeling the thermal and physical evolution of Mount Sharp's sedimentary rocks, Gale Crater, Mars: Implications for diagenesis on the MSL Curiosity rover traverse
Authors: Borlina Cauê S. , Ehlmann Bethany L. , Kite Edwin S. 
Published: July 2015

AbstractGale Crater, the Mars Science Laboratory (MSL) landing site, contains a central mound, named Aeolis Mons (informally Mount Sharp) that preserves 5 km of sedimentary stratigraphy. Formation scenarios include (1) complete filling of Gale Crater followed by partial sediment removal or (2) building of a central deposit with morphology controlled by slope winds and only incomplete sedimentary fill. Here we model temperature‐time paths for both scenarios, compare results with analyses provided by MSL Curiosity, and provide scenario‐dependent predictions of temperatures of diagenesis along Curiosity's future traverse. The effects of variable sediment thermal conductivity and historical heat flows are also discussed. Modeled erosion and deposition rates are 5–37 µm/yr, consistent with previously published estimates from other Mars locations. The occurrence and spatial patterns of diagenesis depend on sedimentation scenario and surface paleotemperature. For (1) temperatures experienced by sediments decrease monotonically along the traverse and up Mount Sharp stratigraphy, whereas for (2) temperatures increase along the traverse reaching maximum temperatures higher up in Mount Sharp's lower units. If early Mars surface temperatures were similar to modern Mars (mean: −50°C), only select locations under select scenarios permit diagenetic fluids. In contrast, if early Mars surface temperatures averaged 0°C or brines had lowered freezing points, diagenesis is predicted in most locations with temperatures < 225°C. Comparing our predictions with future MSL results on diagenetic textures, secondary mineral assemblages, and their spatial variability will constrain past heat flow, Mount Sharp's formation processes, the availability of liquid water on early Mars, and sediment organic preservation potential.
Tropical cyclone flow asymmetries induced by a uniform flow revisited
Authors: Thomsen Gerald L. , Smith Roger K. , Montgomery Michael T. 
Published: July 2015

AbstractWe investigate the hypothesized effects of a uniform flow on the structural evolution of a tropical cyclone using a simple idealized, three‐dimensional, convection‐permitting, numerical model. The study addresses three outstanding basic questions concerning the effects of moist convection on the azimuthal flow asymmetries and provides a bridge between the problem of tropical cyclone intensification in a quiescent environment and that in vertical shear over a deep tropospheric layer. At any instant of time, explicit deep convection in the model generates flow asymmetries that tend to mask the induced flow asymmetries predicted by the dry, slab boundary layer model of Shapiro, whose results are frequently invoked as a benchmark for characterizing the boundary layer‐induced vertical motion for a translating storm. In sets of ensemble experiments in which the initial low‐level moisture field is randomly perturbed, time‐averaged ensemble mean fields in the mature stage show a coherent asymmetry in the vertical motion rising into the eyewall and in the total (horizontal) wind speed just above the boundary layer. The maximum ascent occurs about 45° to the left of the vortex motion vector, broadly in support of Shapiro's results, in which it occurs ahead of the storm, and consistent with one earlier more complex numerical calculation by Frank and Ritchie. The total wind asymmetry just above the boundary layer has a maximum in the forward right sector, which is in contrast to the structure effectively prescribed by Shapiro based on an inviscid dry symmetric vortex translating in a uniform flow where, in an Earth‐relative frame, the maximum is on the right.