bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental investigation of hysteretic dynamic effect in capillary pressure–saturation relationship for two‐phase flow in porous media
Authors: Mirzaei Mahsanam , Das Diganta Bhusan
Published: April 2013

Well‐defined laboratory experiments have been carried out to investigate hysteretic dynamic effect in capillary pressure–saturation relationships for two‐phase flow in homogeneous and heterogeneous (layered) porous media. Conceptually, the dependence of the capillary pressure curves on the rate of change of saturation (dSw/dt) is defined as the dynamic effect in capillary pressure relationship, which is indicated by a dynamic coefficient, τ (Pa s) and it determines the rate at which two‐phase flow equilibrium is reached, i.e., dSw/dt = 0 where Sw and t are the water saturation and time, respectively. The dependences of τ on various fluid and porous materials properties have been studied in the context of drainage; but, there is limited study for imbibition and the hysteresis of τ−Sw relationships. As such, the emphasis in this article is on reporting τ−Sw curves for imbibition while also demonstrating the hysteresis in the τ−Sw relationships by comparing τ−Sw curves for drainage (previously reported) and imbibition (this study) in carefully designed laboratory experiments. Homogeneous sand samples composed of either fine (small particle size and lower permeability) or coarse (larger particle size and higher permeability) sand have been used for these experiments. Furthermore, a layered domain made of a find sand layer sandwiched between two coarse sand layers is used as a model of heterogeneous domain. The results of the study confirm that the τ−Sw relationships are hysteretic in nature and, as such, the speed to flow equilibrium should vary depending on whether drainage or imbibition takes place. At a particular water saturation, the magnitudes of the dynamic coefficient (τ) are found to be generally higher for imbibition, which imply that the speed to flow equilibrium at the same saturation will be slower for imbibition. © 2013 The Authors. AIChE Journal, published by Wiley on behalf of the AIChE. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. AIChE J, 59: 3958–3974, 2013
Celebrating singularities: Mathematics and chemical engineering
Authors: Wang Yunshan , Cheng Xinguang , Chang Hsueh‐Chia
Published: April 2013

The authors review and project their group's work in reaction engineering, electrokinetics, thin‐film lubrication/wetting, biosensing, mass spectrometry, etc., that share one common mathematical underpinning: singularities. These can be geometric singularities of actual surfaces or objects, where focused electrical, acoustic, optical and shear‐stress fields produce anomalous physical phenomena that have been explored mathematically with a spectral theory or exploited for specific applications. They are also singularities of mathematical manifolds, such as solution branches and Riemann manifolds, defined by abstract mathematical formulations, so that they can be used to design optical sensors, and understand nonlinear dynamical behavior that is relevant to system control and surface characterization. The common mathematical framework for these diverse topics underscores how mathematics can reveal, organize and inspire real and industrially relevant problems in chemical engineering. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1830–1843, 2013
A boy with Burkitt lymphoma associated with Noonan syndrome due to a mutation in RAF1
Authors: Cianci Paola , Tono Valentina , Sala Alessandra , Locatelli Laura , Carta Claudio , Rizzari Carmelo , Biondi Andrea , Selicorni Angelo
Published: April 2013

This article reports on an association between Burkitt lymphoma and Noonan syndrome (NS) due to a RAF1 gene mutation. The patient was a 7‐year‐old boy with NS, who was included in the first series reporting the association between Noonan and RAF1, and who later presented with a 2‐week history of asymptomatic unilateral tonsillar swelling and ipsilateral cervical lymphadenopathy. Histological and biological examinations of the tonsillar biopsy led to the diagnosis of Burkitt lymphoma. While there is a well‐established association between NS and solid cell tumors, this is the first case described in the literature of Burkitt lymphoma in a patient with NS, and adds to the growing list of data supporting neoplasia's association with NS. © 2013 Wiley Periodicals, Inc.
Deletion of 3p25.3 in a patient with intellectual disability and dysmorphic features with further definition of a critical region
Authors: Kellogg Gregory , Sum John , Wallerstein Robert
Published: April 2013

Several recent reports of interstitial deletions at the terminal end of the short arm of chromosome 3 have helped to define the critical region whose deletion causes 3p deletion syndrome. We report on an 11‐year‐old girl with intellectual disability, obsessive–compulsive tendencies, hypotonia, and dysmorphic facial features in whom a 684 kb interstitial 3p25.3 deletion was characterized using array‐CGH. This deletion overlaps with interstitial 3p25 deletions reported in three recent case reports. These deletions share a 124 kb overlap region including only three RefSeq annotated genes, THUMPD3, SETD5, and LOC440944. The current patient had phenotypic similarities, including intellectual disability, hypotonia, depressed nasal bridge, and long philtrum, with previously reported patients, while she did not have the cardiac defects, seizures ormicrocephaly reported in patients with larger deletions. Therefore, this patient furthers our knowledge of the consequences of 3p deletions, while suggesting genotype–phenotype correlations. © 2013 Wiley Periodicals, Inc.
X‐linked reticulate pigmentary disorder with systemic manifestations: A new family and review of the literature
Authors: Pezzani Lidia , Brena Michela , Callea Michele , Colombi Marina , Tadini Gianluca
Published: April 2013

X‐linked reticulate pigmentation disorder with systemic manifestations (XLPDR) is an extremely rare genodermatosis with recessive X‐linked inheritance but unknown molecular basis. In males, cutaneous involvement is characterized by reticulate hyperpigmentation of the skin that is associated with a typical facies and severe systemic involvement. In the carrier females, manifestations are apparently limited to the skin with patchy linear hyperpigmentation following the lines of Blaschko that are similar to stage III incontinentia pigmenti. Thus far, only five families affected by this disorder have been described. We report on a new family with clinical features of XLPDR and compare it with those reported in the literature. © 2013 Wiley Periodicals, Inc.
Multiple neurofibromas as the presenting feature of familial atypical multiple malignant melanoma (FAMMM) syndrome
Authors: Vanneste Rachel , Smith Erika , Graham Gail
Published: April 2013

Mutations in the cyclin‐dependent kinase inhibitor‐2A (CDKN2A) gene have been associated with a number of malignancies, most notably cutaneous malignant melanoma (CMM). Mutations in this gene have also been associated with pancreatic cancer and breast cancer, as well as astrocytomas and other nervous system tumors (NST). Among NST, rare solitary internal neurofibromas have been reported, but multiple cutaneous neurofibromas have only been described in two families. In the first family, the affected individuals all carried a heterozygous G > C mutation at the splice acceptor site of intron 1 resulting in skipping of CDKN2A exon 2, while the affected individuals in the second family had a deletion that encompassed the whole CDKN2A/CDKN2B/ANRIL locus. We now report on a proposita presenting with multiple biopsy‐proven cutaneous neurofibromas and a solitary spinal neurofibroma found to have a deletion of 14 nucleotides in exon 2 of CDKN2A, providing further evidence that p14, p16, and/or ANRIL are specifically involved in the pathogenesis of neurofibromas as a feature of the familial atypical multiple malignant melanoma spectrum. © 2013 Wiley Periodicals, Inc.
Ritually breakingLapita pots: or, can we get into the minds ofOceanic first settlers? A discussion
Authors: Sand Christophe , Marshall Yvonne , Sheppard Peter , Spriggs Matthew , Chiu Scarlett , Sand Christophe
Published: April 2013

One of the striking characteristics of Lapita archaeology during the past century has been the very limited number of preserved whole or nearly whole pots found in excavations. This appears odd for ceramics mostly interpreted in the scientific literature as non‐utilitarian and carrying social or ritual symbolism. The clear connection between dentate‐stamped pots and complex burial rituals at theTeouma site (Vanuatu), along with studies on pottery breakage carried out in other parts of the world, allows the canvassing of a theoretical model that explains the apparent absence of logic in finding numerous Lapita pots reduced to small potsherds. By positioning the analysis in a framework relying on the specific behaviour ofPacificIslanders regarding the “invisible” and by using ethnographicMelanesian rituals as examples of how “natural forces” can be controlled, this paper proposes a hypothetical reconstruction of one of the possible ceremonies that may have been practiced byOceanic explorers in newly settled islands.
Optimal Vibration Control for Vehicle Active Suspension Discrete‐Time Systems with Actuator Time Delay
Authors: Han Shi‐Yuan , Tang Gong‐You , Chen Yue‐Hui , Yang Xi‐Xin , Yang Xue
Published: April 2013

This study researches the vibration control approach for vehicle active suspension discrete‐time systems with actuator time delay under road disturbances. First, the discrete‐time models for the quarter vehicle active suspension system with actuator time delay are presented, and road disturbances are considered as the output of an exosystem. By introducing a discrete variable transformation, the discrete‐time system with actuator time delay and the quadratic performance index are transformed into equivalent ones without the explicit appearance of time delays. Then, the problem of original vibration control with actuator time delay is transformed into the optimal vibration control for a non‐delayed system with respect to the transformed performance index. Based on the maximum principle, the feedforward and feedback optimal vibration control law is obtained from Riccati and Stein equations. The existence and uniqueness of the optimal control law is proved. A reduced‐order observer is constructed to solve the physically realizable problem of the feedforward compensator. Finally, the feasibility and effectiveness of the proposed approaches are validated by a numerical example.
Adaptive Decoupling Control of Pulp Levels in Flotation Cells
Authors: Li Haibo , Chai Tianyou , Fu Jun , Wang Hong
Published: April 2013

Control of the pulp levels in flotation cells directly affects the grade of the concentrate and the tailings in a concentration plant. Nevertheless, with strong coupling among cell levels and nonlinearities in the flotation process, conventional control strategies cannot achieve satisfactory control performance. In this paper, a nonlinear multi‐model adaptive decoupling control strategy based on adaptive‐network‐based fuzzy inference systems (ANFIS) is proposed for the flotation process, which includes a linear adaptive decoupling controller, an ANFIS‐based nonlinear adaptive decoupling controller, and a switching mechanism. The proposed method not only improves the transient performance and mitigates effects of the nonlinearities on the system, but also guarantees the input‐output stability of the closed‐loop system. Successful application to the flotation process has been made in a concentration plant in China, and the feasibility and efficiency of the proposed method have been validated.
Separated Maneuvering Target Tracking Algorithm Along with Three Cartesian Coordinates for Three‐Dimension Radar
Authors: Zhang Shicang , Li Jianxun , Wu Liangbin , Zhou Yan
Published: April 2013

When tracking a maneuvering target with a three‐dimensional radar, which can measure range, azimuth, and elevation of the targets, block processing managed by a Markov chain is often adopted under the framework of the interactive multiple model (IMM) estimator. However, tracking performance may degrade because different maneuvers influence each other among three Cartesian coordinates. In order to solve this problem, this paper presents a separated maneuvering target tracking algorithm. First, it formulates the diagonalization and minimization of the upper bound of the modified converted measurement noise covariance matrix as an optimization problem. Then, the existence and uniqueness of the solution for this optimization problem are demonstrated. Finally, it exploits the IMM algorithm to estimate the target states along with each Cartesian coordinate separately. The tracking performance of the proposed algorithm is compared with the square root IMM with L‐D factorization, IMM with sequential importance sampling particles, and multiple‐model estimation with model‐group switching. Monte‐Carlo simulation results demonstrate that the root mean square error of the proposed tracking algorithm is lower than that of the above algorithms for maneuvering target tracking.
Long‐Lived, Directional Photoinduced Charge Separation in RuII Complexes Bearing Laminate Polypyridyl Ligands
Authors: Majewski Marek B. , de Tacconi Norma R. , MacDonnell Frederick M. , Wolf Michael O.
Published: April 2013

RuII complexes incorporating both amide‐linked bithiophene donor ancillary ligands and laminate acceptor ligands; dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz), tetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐h:2′′′,3′′′‐j]phenazine (tpphz), and 9,11,20,22‐tetraazatetrapyrido[3,2‐a:2′,3′‐c:3′′,2′′‐l:2′′′,3′′′]‐pentacene (tatpp) exhibit long‐lived charge separated (CS) states, which have been analyzed using time‐resolved transient absorption (TA), fluorescence, and electronic absorption spectroscopy in addition to ground state electrochemical and spectroelectrochemical measurements. These complexes possess two electronically relevant 3MLCT states related to electron occupation of MOs localized predominantly on the proximal “bpy‐like” portion and central (or distal) “phenazine‐like” portion of the acceptor ligand as well as energetically similar 3LC and 3ILCT states. The unusually long excited state lifetimes (τ up to 7 μs) observed in these complexes reflect an equilibration of the 3MLCTprox or 3MLCTdist states with additional triplet states, including a 3LC state and a 3ILCT state that formally localizes a hole on the bithiophene moiety and an electron on the laminate acceptor ligand. Coordination of a ZnII ion to the open coordination site of the laminate acceptor ligand is observed to significantly lower the energy of the 3MLCTdist state by decreasing the magnitude of the excited state dipole and resulting in much shorter excited state lifetimes. The presence of the bithiophene donor group is reported to substantially extend the lifetime of these Zn adducts via formation of a 3ILCT state that can equilibrate with the 3MLCTdist state. In tpphz complexes, ZnII coordination can reorder the energy of the 3MLCTprox and 3MLCTdist states such that there is a distinct switch from one state to the other. The net result is a series of complexes that are capable of forming CS states with electron–hole spatial separation of up to 14 Å and possess exceptionally long lifetimes by equilibration with other triplet states.
Comparison of methodological data measurement limits in CD4+ T lymphocyte flow cytometric enumeration and their clinical impact on HIV management
Authors: Whitby Liam , Whitby Alison , Fletcher Matthew , Helbert Matthew , Reilly John T. , Barnett David
Published: April 2013

UK NEQAS for Leucocyte Immunophenotyping, an ILAC G13:2000 accredited External Quality Assessment (EQA) organization, with over 3000 international laboratories participating in 14 programmes, issues 2 proficiency testing samples of stabilized whole blood to 824 participants in the Immune Monitoring (lymphocyte subset) programme every two months. We have undertaken a study of 58,626 flow cytometric absolute CD4+ T lymphocyte count data sets from these laboratories over a 12‐year‐period (2001–2012) to determine counting method variation in data measurement limits and how this could influence the clinical management of HIV patients.

Comparison of relative error and 99.9% confidence limits for absolute CD4+ T lymphocyte values was undertaken using dual platform (DP) and single platform (SP) data and showed that the SP consistently outperformed DP, giving lower relative errors and confidence limits at clinically significant absolute CD4+ T lymphocyte counts. Our data shows that absolute CD4+ T lymphocyte counts should be obtained using single platform technology to reduce the variability at clinically relevant levels. On data where results (irrespective of platform) were below the international treatment threshold of 350 cells/μl, there was no significant misclassification between either SP or DP techniques meaning most patients would receive the correct treatment at the correct time. However, results that were above the treatment level of 350 cells/μl had a significant difference (P = 0.04) between DP and SP platforms, suggesting patients monitored using DP technology were 20% more likely to start therapy prematurely than those monitored with SP technology. © 2013 International Clinical Cytometry Society
Removing redundant TCP functionalities in wired‐cum‐wireless networks with IEEE 802.11e HCCA support
Authors: Navarro‐Ortiz Jorge , Ameigeiras Pablo , Ramos‐Munoz Juan J. , Lopez‐Soler Juan M.
Published: April 2013

The TCP was originally designed for wired networks, assuming transmission errors were negligible. Actually, any acknowledgment time‐out unconditionally triggers the congestion control mechanism, even in wireless networks in which this assumption is not valid. Consequently, in wireless networks, TCP performance significantly degrades. To avoid this degradation, this paper proposes the so‐called split TCP and UDP. In this approach, the access point splits the TCP connection and uses a customized and lighter transport protocol for the wireless segment. It takes advantage of the IEEE 802.11e Hybrid Coordination Function Controlled Channel Access (HCCA) mechanisms to remove redundant TCP functionalities. Specifically, the HCCA scheduler allows disabling of the congestion control in the wireless link. Similarly, the IEEE 802.11e error control service makes possible to eliminate TCP acknowledgments, therefore reducing the TCP protocol overhead. Finally, the usage of an HCCA scheduler permits providing fairness among the different data flows. The proposed split scheme is evaluated via extensive simulations. Results show that split TCP and User Datagram Protocol outperforms the analyzed TCP flavors—specifically designed for wireless environments—and the split TCP solution, achieving up to 95% of end‐user throughput gain. Furthermore, the proposed solution is TCP friendly because TCP flows are not degraded by the presence of flows by using this approach. Copyright © 2013 John Wiley & Sons, Ltd.
BOX Structures with Additional Coordination Sites: Potential Ligands for Bifunctional Catalysis
Authors: Seifermann Stefan M. , Muller Thierry , Bräse Stefan
Published: April 2013

The synthesis of four new bis(oxazoline) (BOX) derivatives bearing two additional coordination sites at the 4,4′‐positions is presented. As these BOX scaffolds contain an unsubstituted methylene bridge, they should be capable of forming neutral metal complexes. Thus, these molecules are very interesting ligands for bifunctional catalysis. In addition, one BOX scaffold bearing two azide moieties was successfully employed in copper‐free 1,3‐dipolar cycloaddition reactions. The resulting products have yet again high ligand potential.
Toxicity of magnesium pulses to tropical freshwater species and the development of a duration-based water quality guideline
Authors: Hogan Alicia C. , Trenfield Melanie A. , Harford Andrew J. , van Dam Rick A.
Published: April 2013

Six freshwater species (Chlorella sp., Lemna aequinoctialis, Amerianna cumingi, Hydra viridissima, Moinodaphnia macleayi, and Mogurnda mogurnda) were exposed to 4-h, 8-h, and 24-h Mg pulses in natural creek water. Magnesium toxicity to all species increased with exposure duration; however, the extent of increase and the nature of the relationship differed greatly between species. Based on median inhibitory concentrations (IC50s), and compared with continuous exposure data from a previous study, the increase in toxicity with increasing exposure duration from 4 h to continuous (72–144 h) ranged from approximately 2-fold for Chlorella sp. and H. viridissima to greater than 40-fold for A. cumingi. Moreover, the form of the relationship between Mg toxicity and duration ranged from linear or near-linear to exponential for different species. The life-stage at which M. macleayi was exposed was important, with cladocerans pulsed at the onset of reproductive maturity being approximately 4 times more sensitive (based on IC50s) than younger than 6-h-old neonates. Species sensitivity distributions were constructed for the 4-h, 8-h, and 24-h pulse durations, from which 99% species protection guideline values (95% confidence limits [CLs]) of 94 (6.4–1360) mg/L, 14 (0.5–384) mg/L, and 8.0 (0.5–144) mg/L Mg, respectively, were derived. These values were plotted against exposure duration (h) and polynomial interpolation used to derive a guideline value for any pulse duration within the range assessed. Environ Toxicol Chem 2013;32:1969–1980. © 2013 Commonwealth of Australia. Environmental Toxicology & Chemistry © 2013 SETAC
The effect of spinal cord stimulation frequency in experimental painful diabetic polyneuropathy
Authors: Pluijms W.A. , van Kleef M. , Honig W.M. , Janssen S.P. , Joosten E.A.
Published: April 2013

Background

Spinal cord stimulation (SCS) has been shown to be an effective treatment for painful diabetic polyneuropathy (PDP). An increase of efficacy is needed since only 67% of patients benefit from SCS. This study aimed to develop an animal model for SCS in PDP and study the effect of various stimulation frequencies on the functional outcome. As the pathophysiology of PDP is complex, including vasoconstriction and nerve injury, the frequency of SCS may result in different outcomes.

Methods

Diabetes mellitus was induced by an intraperitoneal injection of streptozotocin in 8‐week‐old female Sprague‐Dawley rats (n = 76; glucose >15 mmol/L; n = 51). A SCS device was implanted at level Th13 4 weeks later. SCS of the dorsal columns was applied for 30 min and the effect on mechanical hypersensitivity was evaluated.

Results

Mechanical hypersensitivity developed in 26 rats, which were included (low‐frequency, n = 6; mid‐frequency, n = 8; high frequency, n = 9; and sham, n = 3). SCS of the dorsal columns was applied for 40 min, and the effect on mechanical hypersensitivity was evaluated. In all treatment groups, SCS resulted in reversal of mechanical hypersensitivity and a clinically relevant reduction was achieved in 70% of animals. No differences in efficacy were found between the different treatment groups.

Conclusions

The pain‐relieving effect of SCS in PDP was studied in an experimental model. Our study shows that SCS on mechanical hypersensitivity in PDP rats is equally effective when applied at low, mid and high frequency.
Ion temperature anisotropy instabilities in planetary magnetosheaths
Authors: Remya B. , Reddy R. V. , Tsurutani B. T. , Lakhina G. S. , Echer E.
Published: April 2013

There has been a lack of understanding why mirror modes are present in planetary magnetosheaths, at comets, and in the heliosheath. Linear theory indicates that the ion cyclotron instability should dominate over the mirror mode instability in electron‐proton plasma. In this paper, we take a new approach. We examine the role of plasma electron temperature anisotropy on the ion cyclotron and mirror mode instabilities. It will be shown that an inclusion of anisotropic electrons with T⊥ e/T∥ e ≥ 1.2 reduces the ion cyclotron growth rate substantially and increases the mirror mode growth rate. The minimum plasma beta for mirror instability dominance (over the ion cyclotron instability) is βp = 0.5.
On the current sheets surrounding dipolarizing flux bundles in the magnetotail: The case for wedgelets
Authors: Liu J. , Angelopoulos V. , Runov A. , Zhou X.‐Z.
Published: April 2013

Using Time History of Events and Macroscale Interactions during Substorms observations from four tail seasons, we study the three‐dimensional structure of the dipolarization front current sheet (DFCS), which demarcates the magnetic boundary of a dipolarizing flux bundle (DFB, the strong magnetic field region led by a dipolarization front) in Earth's magnetotail. An equatorial cross section of the DFCS is convex; a meridional cross section is consistent with a dipolarized field line. The equatorial flow pattern in the ambient plasma ahead of the DFCS exhibits diversions of opposite sense on its evening and morning sides. The magnetic field perturbations are consistent with local field‐aligned current generation of region‐2 sense ahead of the front and region‐1 sense at the front. The median thickness of the DFCS increases from 800 to 2000 km with increasing distance from the neutral sheet, indicating bundle compression near the neutral sheet. On a meridional cross section, DFCS's linear current density (1.2–1.8 nA/m) peaks ~±0.55 l from the neutral sheet (where l is the ambient cross‐tail current sheet half‐thickness, l ~1.5 RE in our database). This peak, reminiscent of active‐time cross‐tail current sheet bifurcation noted in past studies, suggests that the intense but thin DFCS (10 to 20 nA/m2) may be produced by redistribution (diversion) of the extended but weaker cross‐tail current (~1 nA/m2). Near the neutral sheet, the average DFCS current over the dipolarization front (DF) thickness is perpendicular to both the magnetic field interior to the DFB and the average field direction over the DF thickness. Away from the neutral sheet, the average current becomes progressively parallel to the internal field and the average field direction. The average current directions are indicative of region‐1‐sense field‐aligned current on the DF. As few as approximately three DFBs can carry sufficient total current that, if redirected into the auroral ionosphere, can account for the substorm current wedge's peak current for a sizable substorm (~1 MA). A collapsing DFB could thus be an elemental substorm current wedge, or “wedgelet,” that can divert a sizable portion of the cross‐tail current into the auroral ionosphere.
Energy transfer across the magnetopause for northward and southward interplanetary magnetic fields
Authors: Lu J. Y. , Jing H. , Liu Z. Q. , Kabin K. , Jiang Y.
Published: April 2013

A three‐dimensional adaptive magnetohydrodynamic (MHD) model is used to examine the energy flow from the solar wind to the magnetosphere. Using the model, we directly compute fluxes of mechanical and electromagnetic energy across the magnetopause surface. For northward IMF, most of the energy flux inflow occurs near the polar cusps on magnetopause. The viscous interaction leads the carrying energy plasma enter into high latitudes of the tail magnetopause and then divert to low‐latitude regions tangentially, where the plasma gets cooler and denser near the flanks of plasma sheet. For southward IMF, the largest electromagnetic energy input into the magnetosphere occurs at the tail lobe behind the cusps, and largest mechanical energy input occurs at near‐equatorial dayside magnetopause. Under southward IMF conditions, mechanical energy transfer is enhanced at the flanks of magnetopause in response to increased IMF magnitude, while more electromagnetic energy input can be identified as increasing solar wind density. Our results suggest that the mechanisms proposed to energy transfer are mainly due to reconnection and viscous interaction processes for northward IMF. For southward IMF, reconnection is the dominant factor in energy transfer. If the electromagnetic energy coupling between the solar wind and the magnetosphere can be interpreted as a proxy for the reconnection efficiency, the average efficiency during northward IMF is about 20% of that for southward IMF under the solar wind conditions we considered.
Influence of a ground‐based VLF radio transmitter on the inner electron radiation belt
Authors: Selesnick R. S. , Albert J. M. , Starks M. J.
Published: April 2013

Observed signatures of electron precipitation from the inner radiation belt are shown to be consistent with the theory of resonant scattering by whistler‐mode plasma waves, assuming the waves originate in VLF radio transmissions from the ground station NWC. The conclusion is based on a stochastic model of electron transport that includes pitch angle diffusion, radial diffusion, energy loss, and azimuthal drift. The wave scattering causes an increase in quasi‐trapped electron intensity, forming the “wisp” signature, and a corresponding decrease in stably trapped intensity at low altitude. A smaller decrease at high altitude is expected to be obscured by inward radial diffusion. If NWC were shut down, the resulting increase in stably trapped electron intensity would be minimal.
The propagation of transient wave packets in highly dissipative media
Authors: Walterscheid R. L.
Published: April 2013

The group velocity of a wave packet is defined in terms of the central wave number. Because of scale‐dependent dissipation, the central wave number migrates to lower values as transient wave packets propagate through dissipative media. The importance of this effect is greater the broader the bandwidth of the wave packet is or the more localized it is spatially. For modest localization, the migration of the central wave number significantly accelerates the vertical motion of wave packets and allows propagation to significantly greater altitudes before packets are substantially dissipated. Wave packets may experience significant attenuation due to dispersion before they begin to experience strong viscous dissipation.
Gyro‐resonant scattering of radiation belt electrons during the solar minimum by fast magnetosonic waves
Authors: Shprits Yuri Y. , Runov Andrei , Ni Binbin
Published: April 2013

In the current study, we perform statistical analysis of the magnetosonic (MS) waves (also often referred to as extremely low frequency (ELF) equatorial noise) in the range between the ion cyclotron frequency and the lower hybrid resonance frequency within 10° of the magnetic equator. Observations were made between 2 and 9 RE using THEMIS Filter Bank (FBK) data. ELF waves with spectral power exceeding 10−6 nT2/Hz are registered in ~3% of all samples in the inner magnetosphere. The survey has shown that, during the solar minimum, the average amplitude of equatorial ELF waves is less than 0.025 nT. Interpreting ELF events as MS waves, we have evaluated the corresponding wave‐induced resonant scattering coefficients of radiation belt energetic electrons. We also study the effect of heavy ions on the scattering rates. The analysis reveals that the scattering by magnetosonic waves for various plasma compositions during geomagnetically quiet times is by up to two orders of magnitude slower than was previously reported and cannot significantly contribute to the long‐term dynamics of the radiation belts. Computed electron scattering rates by magnetosonic waves extends to higher αeq when the fraction of H+ in the plasma decreases, while the range of pitch angles for which resonance occurs remains relatively insensitive to the plasma composition. While inclusion of multi‐ion species into the wave dispersion relation produces noticeable changes in bounce‐averaged scattering rates, the average rates are still significantly below typical scattering rates of chorus or hiss waves.
Is an ionospheric electron enhancement preceding the 2011 Tohoku‐Oki earthquake a precursor?
Authors: Kamogawa Masashi , Kakinami Yoshihiro
Published: April 2013

Heki [2011] reported that the TEC gradually enhanced from 40 minutes before the 2011 M9.0 off the Pacific coast of Tohoku earthquake (Tohoku EQ) to the time when the co‐seismic acoustic wave reached the ionosphere and the TEC immediately recovered at the normal state. This paper shows an alternative interpretation of total electron content (TEC) variation in the ionosphere associated with the Tohoku EQ. Our interpretation is that a tsunamigenic ionospheric hole, a wide depletion of the TEC, occurred after the co‐seismic acoustic wave reached the ionosphere and gradually recovered at the normal state with several tens of minutes [Kakinami et al., 2012]. The difference between Heki [2011] and Kakinami et al. [2012] is attributed to the reference curves of the TEC to extract the ionospheric variations. The former is given by the least‐squares fitting curve of the EQ day data excluding an expected precursor period, while the latter is given by the data of the similar orbit of global positioning system (GPS) satellite on another day. The results suggest that variation of slant TEC is explained by the depletion of TEC due to tsunami rather than the precursory enhancement.
Electrodynamics of the high‐latitude trough: Its relationship with convection flows and field‐aligned currents
Authors: Zou Shasha , Moldwin Mark B. , Nicolls Michael J. , Ridley Aaron J. , Coster Anthea J. , Yizengaw Endawoke , Lyons Larry R. , Donovan Eric F.
Published: April 2013

We present a detailed case study of the electrodynamics of a high‐latitude trough observed at ~ 12 UT (~1 MLT) on 8 March 2008 using multiple instruments, including incoherent scattering radar (ISR), GPS total electron content (TEC), magnetometers, and auroral imager. The electron density within the trough dropped as much as 80% within 6 minutes. This trough was collocated with a counterclockwise convection flow vortex, indicating divergent horizontal electric fields and currents. Together with a collocated dark area shown in auroral images, the observations provide strong evidence for an existence of downward field‐aligned currents (FACs) collocated with the high‐latitude trough. This is further supported by assimilative mapping of ionospheric electrodynamics results. In addition, the downward FACs formed at about the same time as a substorm onset and east of the Harang reversal, suggesting it is part of the substorm current wedge. It has long been a puzzle why this type of high‐latitude trough predominantly occurs just east of the Harang reversal in the postmidnight sector. We suggest that the high‐latitude trough is associated with the formation of downward FACs of the substorm current system, which usually occur just east of the Harang reversal. In addition, we find that the ionospheric electron temperature within the high latitude trough decreases in the F region while increasing in the E region. We discuss possible mechanisms responsible for the complex change in electron temperature, such as ion composition change and/or presence of downward FACs.
Formation of a transient front structure near reconnection point in 3‐D PIC simulations
Authors: Vapirev A.E. , Lapenta G. , Divin A. , Markidis S. , Henri P. , Goldman M. , Newman D.
Published: April 2013

Massively parallel numerical simulations of magnetic reconnection are presented in this study. Electromagnetic full‐particle implicit code iPIC3D is used to study the dynamics and 3‐D evolution of reconnection outflows. Such features as Hall magnetic field, inflow and outflow, and diffusion region formation are very similar to 2‐D particle‐in‐cell (PIC) simulations. In addition, it is well known that instabilities develop in the current flow direction or oblique directions. These modes could provide for anomalous resistivity and diffusive drag and can serve as additional proxies for magnetic reconnection. In our work, the unstable evolution of reconnection transient front structures is studied. Reconnection configuration in the absence of guide field is considered, and it is initialized with a localized perturbation aligned in the cross‐tail direction. Our study suggests that the instabilities lead to the development of finger‐like density structures on ion‐electron hybrid scales. These structures are characterized by a rapid increase of the magnetic field, normal to the current sheet (Bz). A small decrease in the magnetic field component parallel to the reconnection X line and the component perpendicular to the current sheet is observed in the region ahead of the front. The instabilities form due to fact that the density gradient inside the front region is opposite to the direction of the acceleration Lorentz force. Such density structures may possibly further develop into larger‐scale earthward flux transfer events during magnetotail reconnection. In addition, oscillations mainly in the magnetic and electric fields and the electron density are observed shortly before the arrival of the main front structure which is consistent with recent THEMIS observations.
Interhemispheric magnetic conjugacy
Authors: Ganushkina N. Yu. , Kubyshkina M. V. , Partamies N. , Tanskanen E.
Published: April 2013

The concept of the inter‐hemispheric magnetic conjugacy was investigated by comparing the conjugate points in the northern and southern hemispheres using the Tsyganenko T02 magnetic field model together with the International Geomagnetic Reference Field model for the internal magnetic field to follow the magnetic field lines. We studied the influence of the dipole tilt angle, solar wind (solar wind dynamic pressure and flow direction), and interplanetary magnetic field (IMF) parameters (IMF By and Bz) on the latitudinal and longitudinal differences between the foot points of magnetic field lines in both hemispheres. It was found that the dominant difference up to 30° is longitudinal, while latitudinal differences are about 2°. The largest differences are observed at dawn and dusk magnetic local times (MLTs) for large dipole tilt angles during high solar wind dynamic pressure (16–20 nPa) and large IMF By values ( − 15 and 15 nT). The asymmetry of conjugate points is present due to nonzero values of IMF By, but there is no real dependence on the magnitude of IMF By. The influence of IMF Bz on the interhemispheric conjugacy depends on the sign of the IMF Bz but not much on the magnitude. The rotation of the tail current sheet from the Sun‐Earth line by several degrees resulted in latitudinal differences of 1° and longitudinal differences of 15° at dawn and dusk MLTs for equinox. Testing the concept of magnetic conjugacy with previously reported auroral event observed at Tjörnes (Iceland) and Syowa (Antarctica) observatories confirmed the importance of taking into account the solar wind flow direction, especially when it deviates from radial by more than 2°
Impacts of atmospheric ultrafast Kelvin waves on radio scintillations in the equatorial ionosphere
Authors: Liu Guiping , Immel Thomas J. , England Scott L. , Frey Harald U. , Mende Stephen B. , Kumar Karanam K. , Ramkumar Geetha
Published: April 2013

We present a statistical analysis of the amplitudes of GPS scintillations (S4 index) observed throughout 2008–2010 using the satellite radio occultation measurements of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). Here, for the first time, periodic variability in the occurrence of S4 is investigated using these data. Significant variations of S4 with periods of 2.5–4 days (quasi‐3 days) are identified from the observations during postsunset hours (1900–2400 local time) between 15°S– 15°N magnetic latitude during this 3 year interval. Coherence analyses of these variations with the geomagnetic Ap index, solar EUV irradiance, and atmospheric wind measurements from an equatorial mesosphere meteor radar at Thumba, India ( 8.5°N, 77°E) are performed, providing a measure of the relationship between variations in the scintillations and potential drivers. The quasi‐3 day variations in S4 are found to covary with the variations of the three drivers examined. In particular, the S4 signatures are found to be coherent with the atmospheric ultrafast Kelvin (UFK) planetary waves characterized by the zonal wind measurements of the radar. This study shows that these UFK waves are as important as the solar and geomagnetic drivers in forcing the day‐to‐day variations of the occurrence of equatorial spread F.
Synthetic four‐solar‐cycle solar wind at 1 AU generated from the OMNI data set
Authors: Thatcher L.J. , Müller H.‐R.
Published: April 2013

Numerical modeling provides key insights into the physics of the outer heliosphere. The solar wind data utilized by these models impact their accuracy and should be as close as possible to the actual solar wind. Because of the time scales involved, such a data set should also span several solar cycles. Yet the bulk of solar wind measurements in such a time frame was obtained near Earth. A method to infer the solar wind at points not directly observed is developed such that a 1 AU ring in the ecliptic plane is filled with four solar cycles of solar wind data. Hourly OMNI data are used as the seed data. The OMNI data are separated into four separate categories, and those categories are first extrapolated, generating a continuous 2‐D category map of the solar wind for the full four solar cycles covered by OMNI. The category map is used to determine solar wind characteristics. The solar wind values are determined by local running averages coupled with a random walk technique. The averages provide baseline values and the random walk adds short‐duration deviations from this baseline. The statistics from the extrapolated data are compared to the statistics of the original OMNI data set. Category durations, relative coverage, variable distributions, and correlations are similar to those of the OMNI data, although with some discrepancies.
On the origin of the quasi‐perpendicular ion foreshock: Full‐particle simulations
Authors: Savoini P. , Lembege B. , Stienlet J.
Published: April 2013

Many space missions have already evidenced the existence of the ion foreshock region located upstream of the Earth's bow shock and populated by energetic backstreaming ions reflected by the shock front. In order to analyze this region, a curved shock is simulated with a 2‐D particle‐in‐cell (PIC) code. The analysis is presently restricted to the quasi‐perpendicular angular range defined by 45° ≤ θBn ≤ 90°. In agreement with experimental data, present results evidence two distinct ion populations backstreaming from the shock front along the interplanetary magnetic field: (i) the field‐aligned beam population (hereafter “FAB”) and (ii) the gyrophase bunched population (hereafter “GPB”) which differ from each other by their gyrotropic or non‐gyrotropic behavior, respectively. Excluded by a simulation time which is too short, ion instabilities pitch‐angle scattering cannot be the source of “GPB.” Two new criteria are proposed to identify more precisely each population: their interaction time Δtint with the shock front and their downstream penetration depth. These criteria show that (i) the “FAB” population moves back and forth between the upstream edge of the shock front and the overshoot, and is characterized by a Δtint covering several upstream gyroperiods. (ii) In contrast, the “GPB” ions suffer a short interaction time (i.e., 1 < τci). We observe that the “FAB” ions may have different origins although all “GPB” ions seem to be produced by the electrostatic field built up at the shock and are emitted in a burst‐like mode rather than in continuous way.
Simultaneity of Forbush decrease events observed at middle‐latitude neutron monitors
Authors: Lee Seongsuk , Oh Suyeon , Yi Yu
Published: April 2013

Ground neutron monitors (NMs) sometimes observe a sudden reduction in galactic cosmic ray intensity—the so‐called Forbush decrease (FD) event. Such events are mainly associated with interplanetary coronal mass ejections passing around the Earth and corotating interaction regions in the heliosphere. Some FD events are observed globally, either simultaneously or nonsimultaneously, at different NM stations in the case that the simultaneity is determined by the overlapping of the FD main phase, with the period of the cosmic ray intensity decreasing before returning to a steady state. Previous studies have identified two types of FD events with statistically significant differences in the distributions of the main phase onset time. It has been hypothesized that simultaneous FD events occur when a strong magnetic cloud passes by the Earth through the central part of the magnetic barrier, whereas nonsimultaneous events occur if a weaker magnetic cloud passes on the duskside of the magnetosphere. However, the previous statistical analyses were performed using only data from high geomagnetic latitude NM stations in the Northern Hemisphere. To address this shortcoming and to further test the above hypothesis, we repeated the analysis using data from NM stations located at middle latitudes (Jungfraujoch, Irkutsk, and Climax), employing cutoff rigidities 3–6 GV for the last solar maximum period (1998–2002), spanning the same time period as Oh et al. (2008) that employed high‐latitude NM stations. The results of the present statistical analysis support the above hypothesis with high confidence levels.
Signatures of magnetospheric injections in Saturn's aurora
Authors: Radioti A. , Roussos E. , Grodent D. , Gérard J.‐C. , Krupp N. , Mitchell D. G. , Gustin J. , Bonfond B. , Pryor W.
Published: April 2013

We report on the evolution of auroral structures based on two 3 h sequences of Saturn's northern hemisphere obtained with the UVIS instrument on board Cassini, and we discuss their possible association with injections in the magnetosphere of Saturn. Simultaneously with the UV auroral structures, we observe Energetic Neutral Atom (ENA) enhancements which are indicative of a rotating heated plasma region possibly related to magnetospheric injections. We examine the possibility that the UV auroral structures reported here are triggered by energetic particle injections by investigating (a) the evolution of the longitudinal extent of an injection and (b) its energy density, properties that change with time due to dispersion and ion/electron losses. We simulate the auroral counterpart of an injection considering that the precipitating energy flux could be provided to the ionosphere by pitch angle diffusion and electron scattering by whistler‐mode waves. We compare the brightness and size evolution of the simulated ionospheric signature with the observed values, and we demonstrate that the UV auroral structure behaves as an auroral signature of an injection. This comparative study defines characteristics of the injections such as the spectral index and the electron energy range as well as the magnetospheric corotation rate. Additionally, based on the simultaneous ENA‐UV emissions, we discuss the possibility that pitch angle diffusion and electron scattering may not be the only mechanism responsible for the observed auroral emissions. Field‐aligned currents driven by the pressure gradients along the boundaries of the injected hot plasma cloud could be also considered to play a role on how injections create auroral emissions at Saturn.