ALBERT

Description: Ground-based observations have shown Pi1B magnetic pulsations are associated with substorm onset. These pulsations can also be observed at geosynchronous orbit, suggesting that they propagate from (or beyond) geosynchronous orbit to the ionosphere at substorm onset. Independently, investigations have shown that the initial brightening of an arc at subtorm onset is Alfvénic in nature (i.e., that the aurora during the initial brightening is wave-driven). These results raise the question of whether Pi1B pulsations might drive Alfvénic aurora at substorm onset. In this paper, data from a single event are presented that show Pi1B pulsations observed simultaneously at geosynchronous orbit, by FAST just above the ionosphere and by various ground stations. The event is observed by FAST within a few minutes of the onset of Pi1B pulsations, with an electron signature of the onset arc that is quite characteristic of Alfvénic aurora, showing that at least a portion of the initial brightening is wave-driven and associating this with the presence of Pi1B pulsations. The implication of this work is that Pi1B pulsations propagate to the ionosphere from beyond geosynchronous orbit and provide the wave power to drive Alfvénic aurora at substorm onset, at least for this single, isolated event. The luminosity associated with the Alfvénic aurora, however, may only provide a small contribution to the total brightness.

Description: The dc electrical stability of ZnO varistors was effectively improved by controlling the composition proportion of Bi 2 O 3 and SiO 2 as well as annealing condition. The microstructure, current–voltage ( I – V ) property, and dc degradation characteristics are significantly affected by the molar ratio of Bi 2 O 3 to SiO 2 in composition. It is found that a phase transition from β-Bi 2 O 3 (with dissolved Si) to Bi 12 SiO 20 , with a volume contraction of 5.88%, occurred after annealing at 850°C. The formed Bi 12 SiO 20 plays an important role in improving the electrical stability by inhibiting the oxygen-desorption at the grain boundary.

Description: We report observations of very large amplitude whistler mode waves in the Earth's nightside inner radiation belt enabled by the STEREO Time Domain Sampler. Amplitudes range from 30–110 mV/m (zero-peak), 2 to 3 orders of magnitude larger than previously observed in this region. Measurements from the peak electric field detector (TDSMax) indicate that these large-amplitude waves are prevalent throughout the plasmasphere. A detailed examination of high time resolution electric field waveforms is undertaken on a subset of these whistlers at L 〈 2, associated with pump waves from lightning flashes and the naval transmitter NPM in Hawaii, that become unstable after propagation through the ionosphere and grow to large amplitudes. Many of the waveforms undergo periodic polarization reversals near the lower hybrid and NPM naval transmitter frequencies. The reversals may be related to finite plasma temperature and gradients in density induced by ion cyclotron heating of the plasma at 200 Hz, the modulation frequency of the continuous-mode NPM naval transmitter signal. Test particle simulations using the amplitudes and durations of the waves observed herein suggest that they can interact strongly with high-energy (〉100 keV) electrons on a time scale of

Description: Dense (1- x )BaTiO 3 - x BiYbO 3 (BBTYb) ceramics were fabricated by the solid state reaction method. According to X-ray diffraction data, the average crystal symmetry of x ≤ 0.04 ceramics is described by the non-centro symmetric tetragonal P 4 mm space group, whereas the average crystal symmetry of x ≥ 0.06 ceramics is better described by the centrosymmetric cubic Pm m space group. Raman spectroscopy supports a change in the average crystal symmetry at x ≥ 0.06, but also reveals differences in the local crystal structure for x ≤ 0.04. In this compositional range, BBTYb ceramics undergo a so-called ferroelectric-to-relaxor crossover, which is a manifestation of the continuous modification of local structure. Weak-relaxor behavior was observed in x ≥ 0.06 ceramics, for which the local crystal symmetry departs from cubic, as indicated by the presence of Raman spectra.

Description: In this paper, we report a long-term study of medium-scale traveling ionospheric disturbance (MSTID) occurrence using all-sky images of O I 630 nm airglow emission. Our study is based on a 10.5 year data series in which 5.5 years compound a new data set. The images were obtained by an all-sky imager installed at Cachoeira Paulista (22.7°S, 45°W, 15°S magnetic latitude). Our results show the greatest occurrence of MSTIDs during solar minimum and a minor occurrence rate during descending and ascending solar activity periods. During solar maximum, we have not detected MSTID signatures on all-sky images. All detected events have occurred during geomagnetically quiet conditions. Simultaneous measurements using both all-sky images and ionograms obtained at the same site show the occurrence of spread F and a sharp rise in the ionospheric F layer at the same time as dark bands are optically registered over the zenith. It is possible that for certain weaker events, the ionosonde may resolve bands that are not sufficiently raised to cause darkening of the all-sky images. In order to investigate this possibility, we have conducted a study using only ionograms for a 1 year period (March 2000–February 2001) during solar maximum, when we have not seen any MSTID events in the all-sky images. As we conjectured, MSTIDs also occur during solar maximum, and the risings of the ionospheric F layer are not able to disturb the airglow layer during such events.

Description: Rare earth (RE)-doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of postceramming. The main characteristics of the RE-doped oxide nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline-earth element used as phase-separating agent. Magnesium and erbium co-doped fibers were fabricated. Optical transmission in term of loss due to scattering as well as some spectroscopic characteristics of the erbium ions was studied. For low Mg content, nano-scale particles could be grown with and relatively low scattering losses were obtained, whereas large Mg-content causes the growth of larger particles resulting in much higher loss. However, in the latter case, certain interesting alteration of the spectroscopic properties of the erbium ions were observed. These initial studies should be useful in incorporating new doped materials to realize active optical fibers for constructing lasers and amplifiers.

Description: A novel two-step process has been developed for the preparation of Ba 0.9 Ca 0.1 TiO 3 plate-like grains with [110]-crystal-axis-orientation. In the first step, plate-like particles of a layered titanate H 1.07 Ti 1.73 O 4 are solvothermally treated in a Ba(OH) 2 –Ca(OH) 2 mixed solution, and then in the second step, heat-treat the solvothermally treated sample to complete the formation reaction of Ba 0.9 Ca 0.1 TiO 3 . The formation reaction and nanostructure of the Ba 0.9 Ca 0.1 TiO 3 plate-like grains were characterized using X-ray diffraction, FE-SEM, TEM, and SEAD. The Ba 0.9 Ca 0.1 TiO 3 plate-like grains are constructed from spherical nanoparticles with particle size of about 10–20 nm. The spherical nanocrystals in each plate-like grain arrange in the same crystal-axis-orientation direction, which presented a diffraction pattern similar to the single crystal. The Ba 0.9 Ca 0.1 TiO 3 plate-like grains were utilized to fabricate an oriented Ba 0.9 Ca 0.1 TiO 3 ceramic to demonstrate the potential application of the plate-like grains, and the [110]-oriented Ba 0.9 Ca 0.1 TiO 3 ceramic with a high degree orientation of F 110 = 76% and small grain size of about 1–2 μm was obtained.

Description: The surface and interface enthalpies of CeO 2 were studied by high temperature oxide melt solution calorimetry combined with water adsorption calorimetry. The surface enthalpies of the hydrated and anhydrous surfaces are 0.86 ± 0.02 and 1.16 ± 0.02 J/m 2 , respectively. The water adsorption enthalpies are similar for nano and bulk ceria; for the nano ceria the integral adsorption enthalpy for chemisorbed water relative to water vapor is −59.82 ± 0.74 kJ/mol with coverage of 8.79 ± 0.39 H 2 O/nm 2 and for the bulk it is −61.69 ± 1.26 kJ/mol with coverage of 8.15 ± 0.66 H 2 O/nm 2 . The interfacial enthalpy is 0.81 ± 0.14 J/m 2 . The obtained energies are in good agreement with reported data from atomistic simulations and less direct experimental determinations.

Description: Silicon nitride exhibits fatigue based on cyclic crack propagation which is critical for components under repeated loading. Lifetime predictions for such components are usually based on power law formulations and are most sensitive to the crack growth exponent n . Various statistical procedures exist to determine the parameters from cyclic tests of un-cracked smooth samples. In this work, an analysis is presented for silicon nitride (SL200) lifetime data with a focus on the relation between load ratio and the exponent n . It is found that n increases with the load ratio which has also been observed for macroscopic cracks in silicon nitride earlier. A high degree of uncertainty is associated with the crack growth exponent due to the sparse lifetime database. A pooling strategy is presented which increases the sample size of the underlying lifetime distribution and successfully decreases the scatter in the crack propagation curves and the uncertainty in the crack propagation exponent and, thus, in the lifetime prediction.

Description: A novel high-throughput combinatorial library preparation technique for ceramics requiring low levels of dopant is demonstrated and assessed for the case of donor-doped barium titanate (BT) materials with positive temperature coefficient of resistance (PTCR). The droplet-doping process is performed by infiltrating liquid dopant precursors into porous BT disks and viewed using a high-speed camera. The resulting dopant distribution in the body of the disk shows high uniformity as assessed by energy dispersive (EDS) and wavelength dispersive (WDS) spectroscopies. X-ray diffraction (XRD) measurements and resistivity–temperature (ρ– T ) curves show evidence of the changes in structure and PTCR profiles with change in composition and are closely matched to previously published data for samples made by conventional ceramic routes. The procedure, thus validated, has the potential to deliver dopant-doped BT-based PTCR libraries rapidly with a very wide range of dopant mixtures and concentrations for electrical property measurement and deserves to be applied to other low-level dopant ceramic systems.

Description: We reproduce a magnetospheric reconfiguration under southward interplanetary magnetic field (IMF) conditions using numerical magnetohydrodynamic simulations. To investigate the relative displacements of the geomagnetic conjugate points, we trace both footprints of the geomagnetic field lines during the magnetospheric reconfiguration under positive and negative IMF By conditions. Several substormlike features, namely, the formation of a near-Earth neutral line, a fast earthward flow, and tailward releases of the plasmoid, occur about 1 h after a southward turning of the IMF. The surveyed field line traced from the near-Earth magnetotail was strongly distorted duskward in the north and south after the substorm onset for positive and negative IMF By, respectively. The maximum of the relative longitudinal displacement of both footprints is 4.5 and 5.5 h in magnetic local time for positive and negative IMF By, respectively. While observational studies have indicated that the IMF orientation is the main factor controlling the relative displacement of the conjugate points, the present simulation-based study with a constant IMF orientation shows for the first time that the combined effects of plasma pressure, magnetic field intensity, and the field-aligned current density distribution along the field line are likely to be major factors controlling the relative displacement of conjugate points.

Description: Motivated by recent attempts to derive geomagnetic activity from hourly mean data in long-term studies, we test the recursive Kalman filter method to obtain the regular solar variation curve of the geomagnetic field. Using a simple algorithm, we are able to assign a quiet day curve to every day separately, without the need for additional input parameter(s) to define the geomagnetically quiet days. We derive a digital counterpart AhK of the analog range index Ak at the subauroral Sodankylä station and compare it to the earlier digital estimate Ah and the local Ak index. We find that the new method outperforms the former estimate in every aspect studied and provides a robust, straightforward manner of estimating and verifying the manually scaled Ak index, based on readily available hourly values. The model is independent of sampling; thus, for shorter-term studies where high-sampling data are available, more accurate estimates can also be obtained when needed. Therefore, in contrast to other recent approaches, we do not provide a method to quantify irregular activity directly but derive the actual quiet day curves in the traditional manner. In future applications the same algorithm may be used to define a wide variety of geomagnetic indices (such as Ak, Dst, or AE).

Description: This article reports the target and liquid media influences on the microstructures and optical properties of ZnO nanoparticles synthesized using pulsed laser ablation (PLA) method. Zinc and ZnO target were ablated with laser in pure water and surfactant solution, respectively. The obtained nanoparticles were characterized using X-ray diffraction spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, optical absorption spectrum, and photoluminescence spectrum. The nanoparticles synthesized in surfactant solution were of spherical shapes, but with different microstructures and optical properties. The nanoparticles synthesized in water using zinc target showed rod shapes and both UV and visible emissions. When ZnO target was ablated in water, flake-shaped nanoparticles were synthesized and strong UV, but weak violet emissions were observed. At last, the influences of PLA growth condition on the nanoparticles microstructures and the relationship between the optical properties and their stoichiometries were discussed.

Description: The (1- x )PbTiO 3 - x BiMeO 3 (Me = Fe, In, Sc) solid solutions were prepared and investigated using high-temperature X-ray diffraction for the B-site dopant effect on their thermal expansion behaviors. Compared with PbTiO 3 , the negative thermal expansion of (1- x )PbTiO 3 - x BiFeO 3 was enhanced, whereas that of (1- x )PbTiO 3 - x BiInO 3 was a little weakened and was much weakened in (1- x )PbTiO 3 - x BiScO 3 . An empirical linear correlation between the average effective radius of the B-site cations and the unit cell volumes at Curie point of the solid solutions was concluded. The relationship was also observed in other PbTiO 3 -BiMeO 3 -type solid solutions and was supposed to be widely useful in predicting the thermal expansion coefficient of compounds of this sort. Above the Curie point, the unit cell volumes of the compounds were determined by the radii of the doped B-site cations. The weaking and vanishing of the lattice distortion caused by spontaneous polarization displacements was proved by Raman scatting spectrum, which supported the relationship in the lattice dynamic aspect.

Description: A new route to synthesize SiCN(O) precursor is adopted with vinyl trichlorosilane and solid ammonia carbamate as starting materials. The reaction is controlled in autoclave. A mixture of solid oxygen-rich polysilazane and ammonia chloride is obtained for the reason of dimensional poly-condensation. It is adopted to take the byproduct apart using chemical vapor transportation. The mixture is pyrolyzed at 1100°C for 2 h in Ar, and black SiCN(O) powder is separated from the byproduct. The chemical component of the powder is Si 1.00 C 2.07 N 1.09 O 0.29 . XRD analysis indicates that the black powder keeps amorphous at a temperature up to 1450°C. At 1500°C, SiC phase is first precipitated. With the temperature further increased, Si 2 N 2 O phase appeared. It provides a way to separate other nitrides from ammonia chloride in similar system.

Description: An experimental investigation of the temporal dynamics of the magnetic zenith (MZ) effect associated with ionospheric modification by high-power HF electromagnetic waves is presented. The observed electron temperature enhancement when the heater beam and the UHF radar are directed along the magnetic zenith is at least twice that observed when the heater and radar are both directed vertically. It is shown that the temperature enhancement reaches the stationary state within 10 s after the heater is turned on. Such times (∼5–10 s) are typical for the development of striations with transverse sizes of the order of several meters. Also, the temporal behavior of the ion line spectra is analyzed for the field-aligned and vertical directions of the UHF radar. A new theoretical explanation is suggested for the aspect sensitivity of the electron temperature enhancement that explains the fast manifestation of the MZ effect. Furthermore, it is shown that maximum electron heating is achieved at some intermediate inclination angle of the heater beam between the MZ and the Spitze angle. An estimate of the angle within which the maximum heating effect exists is presented.

Description: This paper for the first time reports global three-dimensional (3-D) structures of the ionospheric midlatitude trough using electron density profiles derived from the GPS radio occultation experiment on board FORMOSAT-3/COSMIC (F3/C) satellites during the solar minimum period, February 2008 to January 2009. Results show that the midlatitude trough extends from dusk to dawn in all four seasons and is most pronounced in the winter hemisphere. The troughs in the two hemispheres are asymmetric, where the trough in the Northern Hemisphere is more evident and stronger than that in the Southern Hemisphere during the equinoctial seasons. In general, the trough minimum position shows a high-low-high latitudinal variation with magnetic local time and occurs at lower latitudes under higher magnetic activity. On the other hand, the midlatitude trough structures become more complex in the Southern Hemisphere because of the nighttime plasma density enhancement of the Weddell Sea Anomaly. Our results demonstrate that the new data set of GPS radio occultation by F3/C is useful to probe the global 3-D electron density structures of the midlatitude trough.

Description: Nano alumina powders have been synthesized by combustion method using eight new fuels. The effectiveness of key process factors on the production of nanoparticles was investigated and optimized using Taguchi L 16 array design. The products were characterized by XRD, BET, TGA, EDX, FESEM, and TEM analyses. Results demonstrated that the nano-structured aluminum oxide powders had crystal sizes between 7.2 and 13 nm and specific surface areas between 21.0 and 70.0 m 2 /g. The synthesis of γ-alumina was modified to achieve higher specific surface area (122.6 m 2 /g). A nano-network of powders which was woven by alumina nano-fibers was successfully fabricated by the modification route. The length and diameter of fibers were about 160 and 10 nm, respectively.

Description: Aqueous tape casting of yttria stabilized zirconia (YSZ) having very wide particle size range was investigated using bio-polymer, gelatin as binder and glycerol as plasticizer. Best dispersion of YSZ powder was obtained by using an anionic polyelectrolyte DARVAN 821A at pH 7.5. Gelling properties of gelatin, plasticized with water and glycerol have been studied by dynamic shear measurements. Decreasing concentration of gelatin significantly decreases the gelling temperature of it. With the addition of optimum amount of binder and plasticizer, it has been possible to prepare stable YSZ suspension of 45–50 wt% solid loading that exhibited the desired shear-thinning behavior. Green tapes with good flexibility (strain to failure: 12%–24%) and strength (2–3 MPa) with total organics content of 10–14 wt% were obtained. After removal of organics, the tapes were sintered at 1550°C for 3 h. The sintered density of the tapes thus obtained was about 99% of the theoretical density. The grain size of the sintered tape was fairly large (10–20 μm); but the surface of the sintered tape (thickness: 100 μm) did not show any visible porosity.

Description: The phase stability, electronic structure, compressibility, optical and elastic properties of two polymorphs of Ti 3 SnC 2 were investigated using first-principle calculation. α-Ti 3 SnC 2 is confirmed to be the preferred equilibrium phase under high pressure and high temperature. The electronic structure calculations reveal that the Ti and C atoms form a strong Ti1-C-Ti2-C-Ti1 covalent bond chain while the bonding between Ti1 and Sn is relatively weak. In the low frequency range from radio waves to visible light, Ti 3 SnC 2 behaves similarly with TiC. This material exhibits anisotropic compressibility under hydrostatic pressure: it is more compressible along the c -direction than along a -direction, related to the different bond stiffness and bond angle changes under high pressure. The second-order elastic coefficients were calculated. For the α-phase, the bulk, B , shear, G , and Young's moduli, E , are calculated to be 169.4, 124, and 197.4 GPa, respectively. The low G / B ratio partially explains why Ti 3 SnC 2 is relatively soft and damage tolerant.

Description: The boron carbide (B 4 C) titanium diboride (TiB 2 ) ceramic eutectic is being investigated for armor and tribological applications. Electron diffraction shows [11 0] TiB 2 //[21 1] B 4 C//growth direction, (0001) TiB 2 //( 2 0) B 4 C is parallel to the interface plane, and transmission electron microscopy (TEM) imaging reveals no interface phase. Thermal residual stress distributions are calculated via finite element modeling of an experimental eutectic microstructure. The B 4 C matrix is found to be about 400 MPa in compression, and the TiB 2 lamellae approximately 1.3 GPa in tension. Stress and strain energy concentrations are found at the tips of TiB 2 lamellae. TEM of deformed materials correlates well with the finite element calculations, showing preferential fracture in areas of stress concentration. Interfacial delamination and crack deflection are also observed in deformed materials.

Description: In this report we present a temporal relationship between ground Pi2 and auroral kilometric radiation (AKR). We analyzed six isolated substorm events, which were observed by the MAGDAS/CPMN ground magnetometer network and the plasma wave instrument onboard the Polar satellite. We found that the time derivative of the height-integrated AKR power and the ground Pi2 D component had the same periodicity and that the two were synchronized with each other. When the D component fluctuated with the same (opposite) polarity as the magnetic bay variation, the AKR power tended to increase (decrease) during the corresponding interval. An isolated substorm event (AE ∼ 40 nT), which occurred around 10:19 UT on 24 January1997, was selected for a detailed study. The behavior of the Pi2 event can be interpreted by the substorm current wedge (SCW) and Pi2 propagation models. It is confirmed that the midlatitude and high-latitude D component oscillations can be treated as a proxy of the SCW oscillations, whereas the H component oscillations exhibited some phase shifts by the propagation delay of the Pi2 waves. That is, the temporal relation between the time derivative of the AKR power and the ground Pi2 suggests that the height-integrated AKR power was modulated coherently with the SCW oscillations.

Description: Polymer-mediated interaction forces between an α-alumina particle and c-sapphire surfaces in methylcellulose solutions were measured by the atomic force microscope colloid probe technique. The effect of water soluble methylcellulose on normal and lateral surface forces was probed to understand the binding action of methylcellulose polymers. Methylcellulose bridgings up to ~300 nm in length have been measured. However, pretreatment of surfaces with NH 4 + salt of poly(acrylic acid) resulted in fewer bridging events, probably due to preferential adsorption. The presence of methylcellulose bridging in friction loops was also measured in the form of superimposed spikes.

Description: An optimum TiO 2 seed layer is said to facilitate nucleation and subsequent growth of perovskite phase in Pb(Zr,Ti)O 3 (PZT) films during annealing. The actual causes that prevent perovskite growth, particularly in sputtered PZT films on thick TiO 2 seed layers are not yet understood clearly. Herein, based on the results of X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and analytical scanning/transmission electron microscopy (S/TEM) with semi-quantitative elemental mapping using energy dispersive X-ray (EDX) spectrum imaging, the post-annealing crystallization trend of r.f. magnetron sputter-deposited amorphous PZT films has been scrutinized as a function of TiO 2 seed layer thickness. Upon annealing, PZT films on thin TiO 2 layers (~20–100 nm) partially crystallize into perovskite PZT via a transient pyrochlore/fluorite phase. However, no perovskite phase forms on thicker (~550 nm) TiO 2 layer. Thickness of underlying TiO 2 seed layer strongly influences the crystallization, phase formation, texture, and surface morphology of the PZT films. During crystallization, Pb diffuses away from the PZT film to form solid solution with TiO 2 seed layer. Perovskite PZT phase transformation requires a minimum Pb-concentration within the transient pyrochlore/fluorite phase. During the growth of perovskite grains, Zr gets segregated, resulting in Zr-concentration build-up within the surrounding disordered fcc fluorite phase.

Description: Using a convenient solid-state reaction Ce 0.67 Tb 0.33 Mg 1- x Mn x Al 11 O 19 green phosphors were prepared. The effect of Mn 2+ doping on the luminescence properties, energy transfer mechanism, and color gamut under 254 nm excitation were investigated. The energy transfer from (Ce,Tb) 3+ to Mn 2+ was found to be due to multipolar interactions of the dipole–quadrupole mechanism from theoretical fitting results. The critical distance was calculated to be 0.797 nm. When the Mn 2+ doping content was increased from 0 to 0.12, the energy transfer efficiency (Ce 3+ ,Tb 3+  → Mn 2+ ) gradually increased from 0% to 58%. The Ce 0.67 Tb 0.33 Mg 0.88 Mn 0.12 Al 11 O 19 sample exhibits 105% of the standard NTSC color gamut. Results indicate that Ce 0.67 Tb 0.33 Mg 0.88 Mn 0.12 Al 11 O 19 green phosphors can be applied to illumination devices and displays.

Description: Highly infrared transparent tetragonal ZrO 2 (3 mol% yttria-stabilized) was prepared by means of high-pressure spark plasma sintering (HP-SPS). The crystallite size of the resulting dense sample was about 80 nm. In-line transmittance for the 1.5 mm thick sample ranged between 63% and 67% in the wavelength of 3–5 μm, representing 81%–87% of the theoretic value. Meanwhile, the cutoff wavelength of tetragonal ZrO 2 was superior to the values of other high-strength transparent ceramics. This study highlighted the efficiency and simplicity of HP-SPS for obtaining transparent tetragonal ZrO 2 and the great potential of this ceramic applied for durable infrared windows.

Description: We propose a simple and environmentally friendly method to prepare uniform-sized spherical ceramic foams (SCFs) with excellent pore properties by combining a drop-in-oil method with agar gelation. In addition, the change in size distribution and uniformity (characterized as coefficient of variation (C.V.)) and the corresponding pore-related properties for the SCFs were systematically investigated as functions of agar concentration (i.e., 0.50–1.50 wt% with respect to dry alumina). The results showed that uniform-sized SCFs were successfully fabricated regardless of agar concentration, that pore-related properties were gradually improved by increasing the agar content, and that the most uniform-sized SCFs were obtained when the agar concentration was 1.00 wt%. The extent of the improvement in size uniformity was evaluated by comparing the C.V. value for the drop-in-oil method with that for the pseudo-double-emulsion (PDE) method, which is an alternative method to fabricate SCFs. The C.V. values for the SCFs prepared by the drop-in-oil and the PDE method were determined to be 7% and 31%, respectively. The results clearly indicate that the size uniformity of the SCFs has been much improved for the drop-in-oil method as compared to the PDE method.

Description: Nanostructures of crystalline orthorhombic sodium niobate (NaNbO 3 ) were synthesized by a molten salt synthesis procedure. As a comparison, an auxiliary experiment via conventional solid state reaction process was carried out simultaneously. The microstructure and morphology evolution of the synthesized nano particles were investigated in detail, and on the basis of the experimental results, an in situ transformation mechanism has been proposed to elucidate the formation processes of NaNbO 3 microstructures. It was found that both the initial shape of the Nb 2 O 5 and the dissolution rate of the initial precursors critically determine the final shapes of the products. Furthermore, the determined electrical properties of the as-obtained products indicated that NaNbO 3 ceramic derived from nanostructures holds the real characteristic of ferroelectric and the polarization–electric field ( P–E ) hysteresis behavior is greatly influenced by the polarization treatment. The obtained NaNbO 3 ceramic after the polarizing treatment exhibited piezoelectric property, d 33  = 28 pC/N.

Description: Yttrium tetraboride was synthesized by reactions of Y 2 O 3 with B 4 C or with a B 4 C/C mixture. Fully dense YB 4 ceramics were prepared by hot-pressing at 1800°C and 20 MPa in He. The flexural strength and microhardness of the YB 4 were about 300 MPa and 27 GPa, respectively. Pure YB 4 showed considerable oxidation above 1200°C. The effect of SiC, AlN, and AlN/SiC on the properties of YB 4 ceramics was characterized. No chemical interactions were identified in the YB 4 –SiC and YB 4 –AlN pseudo binaries. The addition of SiC improved the oxidation resistance below 1200°C. At higher temperatures, the low viscosity of a surface melt caused its continuous runoff and the loss of the oxidation-protection capability of the scale. The addition of AlN/SiC improved the oxidation resistance compared to the ceramics containing only SiC, which was attributed to the presence of Al 2 O 3 in the Y 2 O 3 –SiO 2 –B 2 O 3 glass leading to an increase in its viscosity and preventing glass runoff. A significant improvement in the oxidation resistance of the YB 4 ceramics and extension of their oxidation stability to 1400°C was accomplished by the introduction of AlN only.

Description: The energy transfer from Tb 3+ to Eu 3+ -doped SiO 2 (SiO 2 :Eu 3+ , Tb 3+ ) inverse opal photonic crystals was investigated by photoluminescence and fluorescence lifetime. The results showed that the photonic band gap enhanced energy transfer from the donor Tb 3+ to the acceptor Eu 3+ . When the fluorescence emission wavelength of Tb 3+ overlaps the photonic band gap, the fluorescence intensity of Tb 3+ is suppressed, and the fluorescence intensity of Eu 3+ is increased because of the enhancement of energy transfer. In addition, the fluorescence lifetime of Tb 3+ decreased.

Description: Three-dimensional electron backscatter diffraction was used to measure the crystallographic distribution of the electrochemically relevant triple phase boundary lines and surfaces near them in SOFC cathodes made up of a porous mixture of yttria-stabilized zirconia and lanthanum strontium manganese oxide, both before and after mild electrochemical loading. All distributions were observed to be nearly isotropic, but non-random textures above the detection threshold were observed. The distributions differ between the two cells, as do the phase fractions and the electrochemical history. The different distributions are interpreted as evidence that steady-state distributions vary locally with phase fractions or that they evolve during the initial operation of the fuel cell. The rates at which triple lines, pore surfaces, and interface boundaries in the porous mixture approach a steady-state value appear to decrease with the average amount of mass transport required to reorient that specific feature. This work provides initial insights into the crystallography of interfaces in a multiphase ceramic material.

Description: Pb x Sr 1-x TiO 3 (PST) thin films with the ratio Pb/Sr = 40/60 were deposited on silicon substrate with Pt or LaNiO 3 (LNO) bottom electrodes by radio frequency magnetron sputtering followed by a postannealing treatment. The structural and microstructural analyses were performed and a perovskite phase was obtained whatever the nature of the bottom electrodes and even at a low temperature (450°C). The optimal annealing temperature is 650°C at which the films have a dense and fine microstructure. For electrical characterization the different top electrodes (Pt and LNO) were used. In both cases, we demonstrate that PST films present excellent performances in terms of dielectric properties and in particular, the tunability and Figure of Merit. A large tunability (57% at 400 kV/cm) and low dielectric losses (1.4%) were measured at 10 kHz for Pt/PST/Pt structures postannealed at 500°C. For LNO/PST/LNO structures, postannealed at 650°C, the improved tunability (≈80%) and low loss factor (≈2%) were obtained. Prospects of PST as an alternative to BST for tunable applications with a real potentiality of monolithic integration with silicon, in terms of thermal budget, are considered.

Description: Using data from the high-energy neutral atom (HENA) imager onboard the IMAGE satellite, we examined the relation between the SYM-H index and the ring current energy during a storm main phase. The energy range of the energetic neutral atom (ENA) flux data used here is 16–120 keV for hydrogen and

Description: Using observations from the THEMIS spacecraft, we investigate the modulation of whistler mode chorus waves in the magnetosphere by compressional Pc4–5 pulsations (i.e., pulsations with periods from tens of seconds to a few minutes) with an anticorrelation between the total electron density and the background magnetic field intensity. We find that such compressional pulsations are associated with modulations of resonant electron fluxes and chorus intensity. Changes in the total electron density, background magnetic field, and the flux and anisotropy of resonant electrons could all be responsible for triggering the excitation of chorus waves. To quantitatively investigate which parameters dominantly contribute to chorus generation, we evaluate the changes in linear growth rates of whistler mode waves due to variations in either the ratio of resonant electrons to the total electrons R(VR) or the electron anisotropy A(VR). In the majority of cases, the modulation of whistler mode wave intensity is dominated by R(VR) variations caused by compressional Pc4–5 pulsations and tends to occur at large L shells of 8–12 in the dawn sector. Only a small fraction of events are associated with A(VR) modulations and these typically occur at lower L shells (

Description: The 2.7 μm emission has been obtained using 980 nm laser excitation in Er 3+ /Tm 3+ /Pr 3+ triply doped ZrF 4 –BaF 2 –LaF 3 –AlF 3 –YF 3 glass. 2.7 μm emission characteristics and energy transfer are investigated. Population inversion between the 4 I 11/2 and 4 I 13/2 levels is significantly enhanced by way of Tm 3+ and Pr 3+ co-doping into Er 3+ -doped fluoride glass. These results indicate that this Er 3+ /Tm 3+ /Pr 3+ triply doped fluoride glass has potential applications in 2.7 μm laser.

Description: The changes in the ferroelectric and magnetic properties of the nanostructured Pb(Zr 0.52 Ti 0.48 ) 1-x Fe x O 3 (0 ≤ x ≤ 0.06) due to the doping of different amounts of acceptor ions (Fe 3+ ) have been studied. X-ray diffraction studies show that the system maintains the tetragonal phase up to the doping of 2 mol% of Fe 3+ and the formation of secondary phase magnetoplumbite (PbFe 12 O 19 ) on further doping. Electron paramagnetic resonance studies have revealed the formation of defect centers which in turn arise due to the interaction of Fe 3+ ions with oxygen vacancies, which are generated in the lattice. This results in the appearance of room temperature ferromagnetic (RTFM) behavior in the doped samples. The dielectric studies reveal that with the concentration of Fe 3+ the peak near the maxima of dielectric constant (ε′ m ) is broadened. Studies of the defect dipoles on the ferroelectric properties have been performed by polarization measurement. The variations of the above properties with the structural and morphological features of the samples have also discussed.

Description: We combine chelate-assisted solvent extraction (CASE) and hot hydrogen fluoride gas treatment to enable a general method for the preparation of high-purity binary metal fluorides. The fluorozirconate glass ZBLANI:Yb 3+ (ZrF 4 –BaF 2 –LaF 3 –AlF 3 –NaF–InF 3 –YbF 3 ), a solid-state laser-cooling material, is used as a test case to quantitatively assess the effectiveness of the purification method. The reduction of transition-metal and oxygen-based impurities is quantified directly by inductively coupled plasma mass spectrometry (ICP-MS) and indirectly by laser-induced cooling, respectively. The concentrations of Cu, Fe, Co, Ni, V, Cr, Mn, and Zn impurities in the ZrCl 2 O precursor solution were measured individually by ICP-MS at various stages of the purification process. CASE was found to reduce the total transition-metal concentration from 72500 to ~100 ppb. Laser cooling was most efficient in ZBLANI:Yb 3+ glass fabricated from CASE-purified metal fluoride precursors, confirming the results of the ICP-MS analysis and demonstrating the effectiveness of the purification methods in a finished optical material. High-purity metal fluorides prepared by the methods presented herein will enable new high-performance optical materials for solid-state optical refrigerators, crystals for vacuum ultraviolet (VUV) spectroscopy of the Thorium-229 nucleus, VUV optics, fibers, and thin-film coatings.

Description: The boundary of a planetary magnetosphere is the site of mass, momentum, and energy transport. This transport produces a layer of mixed solar wind and magnetospheric plasma inside and adjacent to the boundary. In the case of Earth, the electron structure of this layer is distinctive, and has been explained by models of the layer on open magnetic field lines. In this paper we examine the electron structure of Saturn's low-latitude boundary layer (LLBL) using observations made by the Cassini spacecraft; the typical properties and variability of Saturn's LLBL are examined in a companion paper. By analyzing the relationship between the electron density and temperature measured during Cassini magnetopause crossings we demonstrate that the electron structure of Saturn's LLBL is highly variable. At some of the crossings the structure of Saturn's LLBL is similar to previously reported examples of the structure of Earth's LLBL, where the major changes in electron density and temperature clearly occur in different regions of the layer, producing a distinctive shape to the temperature-density distribution. However, at many crossings the structure of Saturn's LLBL is unlike the previously reported examples of the structure of Earth's LLBL, since they lack the same distinctive shape to the distribution. We discuss the possible explanations for these differences in the electron structure of Saturn's LLBL, and what these differences could tell us about how the solar wind interacts with a planetary magnetosphere.

Description: Fast azimuthal auroral expansion and poleward expansion are characteristic features of the expansion phase of substorms. In the first study of its kind, we have investigated the azimuthal auroral expansion and its magnetospheric counterpart using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers and multiple spacecraft. During the tail season in 2008–2009, we found 16 events of azimuthally expanding aurora that passed near the magnetic footprints of the multiple spacecraft operating in the near-Earth plasma sheet. In the magnetosphere, these events commonly showed fast azimuthal and earthward flows associated with intense electric fields and magnetic dipolarization. The speed of the propagating structure, which was estimated from the time difference of the depolarization observed by the multiple spacecraft, was close to the measured azimuthal plasma flow velocity. We also found that this azimuthal plasma transport was dominated by the E × B drift speed associated with the enhanced electric field. In a statistical analysis, the averaged speeds of the leading edge of the westward and eastward auroral expansion were 8.8 and 5.3 km/s, respectively. When mapped onto the equatorial magnetosphere, these speeds (267 and 162 km/s) were comparable to the averaged azimuthal plasma (E × B) flow speeds observed by the spacecraft, which were 193 (239) km/s in the westward direction and 112 (139) km/s in the eastward direction. Our events showed that E × B flows and auroral expansion predominantly propagated westward, indicating an effect of westward background convection in the Harang flow shear. From these results, we concluded that the azimuthal auroral expansion was closely related to magnetic dipolarization which expanded azimuthally at the E × B drift speed. On the basis of the abrupt formation of the fast E × B flows and their propagation away from the onset location, we suggest that the effects of the intense large-scale electric fields, which are possibly generated through substorm onset turbulence, propagate to the ionosphere along the magnetic field lines and lead to azimuthal expansion of an auroral arc.

Description: The oxidation and scale crystallization kinetics of Hi-Nicalon TM -S SiC fibers were measured after oxidation in dry air between 700° and 1400°C. Scale thickness, composition, and crystallization were characterized by TEM with EDS, supplemented by SEM and optical microscopy. TEM was used to distinguish oxidation kinetics of amorphous and crystalline scales. Oxidation initially produces an amorphous silica scale that incorporates some carbon. Growth kinetics of the amorphous scale was analyzed using the flat-plate Deal-Grove model. The activation energy for parabolic oxidation was 248 kJ/mol. The scales crystallized to tridymite and cristobalite, starting at 1000°C in under 100 h and 1300°C in under 1 h. Crystallization kinetics had activation energy of 514 kJ/mol with a time growth exponent of 1.5. Crystalline silica nucleated at the scale surface, with more rapid growth parallel to the surface. Crystalline scales cracked from thermal residual stress and phase transformations during cool-down, and during oxidation from tensile hoop growth stress. High growth shear stress was inferred to cause intense dislocation plasticity near the crystalline SiO 2 –SiC interphase. Crystalline scales were thinner than amorphous scales, except where growth cracks allowed much more rapid oxidation.

Description: The phase transitions in unpoled lead-free (1− x )(Bi 1/2 Na 1/2 )TiO 3 – x BaTiO 3 ( x = 0.06 and 0.11) ceramics are investigated using hot-stage transmission electron microscopy (TEM). It is found that large ferroelectric domains in both ceramics start to disappear around T d , the depolarization temperature. After the transition, both compositions exhibit the P 4 bm tetragonal symmetry in the form of nanodomains. The structural transition observed by the in situ TEM experiments seems to be gradual and occurs within a temperature range of several tens of degrees, in contrast to the sharp anomaly at T d revealed by the dielectric characterization. With further increasing temperature, no structural change was observed for both compositions across T RE , where the dielectric frequency dispersion vanishes, and T m , where the dielectric permittivity reaches maximum. The tetragonal-to-cubic transition is diffuse and takes place in a broad temperature window well above both T RE and T m . These results of structural phase transitions are summarized in a phase diagram with its composition range covering the morphotropic phase boundary (MPB).

Description: Zinc-blende-type cubic InSe and β-In 2 Se 3 crystallites were synthesized using the solvo-thermal method in this study. The crystalline structure, electronic and optical characterization of indium selenide particles were investigated using transmission electron microscopy (TEM), X-ray diffractometer (XRD), UV–visible absorbance spectra. It was observed that the dominant crystalline structure of samples synthesized at 180°C for 1.5–48 h is zinc-blende-type cubic InSe phase with lattice parameter of about 0.573 nm. As the reaction temperature was raised to 200°C, the zinc-blende-type cubic InSe phase diminished and the β-In 2 Se 3 phase was produced. The zinc-blende-type cubic InSe phase band gap is about 1.68 eV. These synthesized compounds provide promising candidates for solar cell applications.

Description: Upconversion emission of Yb, Er co-doped Bi 4 Ti 3 O 12 (Bi 4 Ti 3 O 12 : Yb, Er) inverse opal photonic crystals was investigated. Strong green (548 nm) and red (660 nm) upconversion emission bands were observed under a 980 nm excitation at room temperature. The results showed that the intensity of upconversion emission bands can be tuned by controlling the structure of the inverse opal. Significant suppression of the green or red upconversion emission was obtained if the photonic band gap overlaps with the Er 3+ ions emission band, resulting in color tunable up-conversion photonic crystals with applications in solid-state color displays.

Description: This article describes a study involving three-dimensional FIB tomographic characterization of Vickers microindentation sites in an alumina material containing pores. The study was carried out using a dual beam FIB instrument for loads in the range 50–200 g. The results obtained show that this technique can be used to obtain 3-D distributions of indentation-generated cracks. Although, compared to a dense material, presence of pores in alumina reduced the ability to generate and/or propagate radial cracks, the significant probability of crack-pore interactions indicates that pores assist in the generation/propagation lateral cracks. The subsurface images show that pores act as sites for crack initiation and/or assist in crack propagation. In addition, a clearly reduced ability to generate and/or propagate radial cracks has been noted. However, considering that FIB tomography is destructive and invasive, microstructural changes seem to have occurred during the process and consequently it is not possible to identify all the generated cracks. Moreover, propagation of some of the cracks also occurred due to material removal in FIB milling.

Description: Mesosporous carbon-bonded titanium-carbide/silicon-carbide (C-TiC/SiC) ceramics with a high specific surface area (221 m 2 /g), ultra fine grains (10–50 nm), and high crystallinity were synthesized from direct carbothermal reduction (1100°–1450°C) of monolithic Ti–Si–O–C precursors made from controlled sol–gel process. The nano-sized carbide grains are bonded into bulk materials by poly(furfuryl alcohol) (PFA) derived nanocrystalline carbon framework by “bridge,” “entanglement,” and “adhesive” effects. Graphenes were found to grow on {111} planes of TiC grains but this was not observed for SiC. The bonding of graphitic carbon layers on carbide grains support the nanostructure and also result in the desired combination of functional and mechanical properties.

Description: Infrared radiative properties of 8-mol%-yttria-stabilized zirconia (8YSZ) ceramics of porosity 3% as applied as electrolyte for solid oxide fuel cells (SOFCs) were studied at room and elevated temperatures in the wavelength range from 2 to 20 μm. The room-temperature directional-hemispherical measurements of reflectance and transmittance for thin samples were combined with normal emittance measurements at several temperatures up to 1700 K. The use of the radiation transfer theory in a region of semi-transparency enabled identification of absorption and scattering properties of the material. Both a detailed numerical procedure using the known discrete ordinates method and a novel iterative analytical solution were employed. An analysis based on the Mie theory confirms volumetric scattering by sub-micron size polydisperse pores in the ceramics. It is shown that the absorption coefficient of 8YSZ increases considerably with temperature. This effect should be taken into account in combined heat transfer calculations for SOFCs.

Description: A Ba 0.75 Sr 0.25 Ti 0.95 Zr 0.05 O 3 ceramic was developed for use in nonlinear transmission line (NLTL) applications. The sol–gel process was used to synthesize Ba 0.75 Sr 0.25 Ti 0.95 Zr 0.05 O 3 nanoparticles to achieve a uniform composition and a high surface area. Simultaneous thermal gravimetric analysis and differential thermal analysis (TGA/DTA) was used to identify the decomposition sequence as a function of temperature for the as-synthesized powders. The phase transformation was confirmed by X-ray diffraction (XRD). The calcined nanoparticles were hot-pressed at 1300°C to achieve a high density. Microstructures were characterized using scanning electron microscopy (SEM). Several dielectric properties were measured and are reported.

Description: Relativistic electron fluxes of the outer radiation belt often decrease rapidly in response to solar wind disturbances. The importance of the magnetopause shadowing (MPS) effect on such electron losses has yet to be quantified. If the MPS is essential for outer radiation belt electron losses, a close relationship between the outer edge of the outer belt and the magnetopause standoff distance is expected. Using GOES and THEMIS data, we examined earthward movement of the outer edge of the outer belt during electron loss events at geosynchronous orbit and its correlation with the magnetopause standoff distance. In events with significant earthward movement, we found a good correlation. There were no clear correlations in events without significant earthward movement, however. Comparing the observational results with a test particle simulation, the observed dependence between the outer edge and the magnetopause standoff distance is consistent with the MPS effect.

Description: An experimental investigation of the physical properties of lightning on Venus was carried out by applying fast impulses to a pressurized (1–2.8 atm) CO2-N2 gas mix. The maximum current employed in the experiments was 2.8 kA. It was found that the pressure has a marked effect on the measured electric field. This effect is mostly due to negative ions created by electron attachment. This negative space charge could hamper breakdown on Venus if the clouds are negatively charged. Using a time-resolved spectroscopic technique, the instantaneous temperature of the arc was measured. This varies from 29,000 K soon after the arc appears to 14,000 K some 15 μs later. The arc's linear resistance and the power it dissipates were estimated using the Spitzer resistivity model and the measured temperatures. The linear resistance was found to be in the 17–233 Ω m−1 interval, which is comparable to the values of terrestrial lightning. The by-products of the discharge were analyzed using a mass analyzer, and it was found that the discharge decomposes the CO2 into CO and O at similar rates. Our estimate of the CO yield is 2.7 × 1018 molecules J−1.

Description: Highly porous ceramics are critical components of Solid Oxide Fuel Cells. Nevertheless, their mechanical properties are poor and not fully understood. Herein, Discrete Element simulations are used to quantitatively assess the relation between the particulate microstructure of highly porous ceramics and their mechanical properties. Partially sintered ceramics are numerically generated with complex microstructures including pore formers and bilayers. These microstructures are then tested in tension and compression to obtain their elastic and fracture behavior. Compiling experimental data from the literature and simulations results, an Orowan–Petch type relation between strength and particle size is proposed for highly porous ceramics. It is based on the local fracture model at the length scale of solid bonds between sintered particles.

Description: We have studied the synthesis and near-infrared luminescent properties of Ni 2+ -doped ZnO–Al 2 O 3 –SiO 2 nanocomposite glasses embedded activated spinel nanocrystals prepared using a sol–gel technique. Nanocrystal-dependent optical properties in Ni 2+ -doped nanocomposite glasses were systematically investigated. We found that Ni 2+ ion is optically active only in the composite embedded nanocrystals, which can provide octahedral position with appropriate crystal field strength. Near-infrared emission ranging from 1100 to 1600 nm was observed in the Ni 2+ -doped composite fabricated by sol–gel method. Such an ultra-broadband luminescence from the nanocomposite could cover the infrared emission bands obtained from multiple rare earth ions (Ho 3+ , Pr 3+ , and Tm 3+ ) doped glasses.

Description: The (1- x - y )K 0.5 Na 0.5 NbO 3 - x CaZrO 3 - y LiNbO 3 (KNLNCZ- x - y ) lead-free piezoelectric ceramics were fabricated by conventional technique, and the effect of the addition of CaZrO 3 and LiNbO 3 on the phase transitions and piezoelectric properties of the KNN-based ceramics was investigated. The addition of CaZrO 3 will shift the orthorhombic-rhombohedral transition temperature of the ceramics to above room temperature, and with the increase of the CaZrO 3 additives, a dielectric peak rises up near the orthorhombic-tetragonal phase transition of the ceramics resulting in the spread of the ferroelectric-paraelectric phase transition over a rather wide temperature range due to polar nanoregions arising from composition fluctuation. For x = 0.05, the addition of LiNbO 3 is effective to shift the T R-O and T O-T downward and T C upward in KNLNCZ-0.05- y ceramics. Optimum piezoelectric properties ( d 33 = 216 pC/N and k p = 42.9%) were obtained for the KNLNCZ- x - y ceramics with x = 0.05 and y = 0.07 due to the decrease of T O-T to be around room temperature.

Description: Alumina-matrix composite containing 2.0 wt% boron nitride nanotubes and monolithic alumina were fabricated by hot pressing, and their thermal and mechanical properties were investigated. Thermal shock resistance was evaluated by water quenching and subsequently by measuring the residual flexural strength by three-point bending test. Though the residual flexural strength of the composite is higher than that of the monolith at temperature differences lower than 280°C, the thermal shock of the composite is more sensitive to temperature change, exhibiting no significant improvement in thermal shock resistance. The variation in thermal shock resistance for the composite is resulted from the introduction of BNNTs.

Description: Since 1980, we have observed the thermospheric neutral wind at the Arecibo Observatory using a Fabry-Perot interferometer to measure the O(1D) 630 nm emission. Burnside and Tepley (1989) examined the first 8 years of this extended data set and found that there were no significant or systematic solar cycle influences on the magnitude or direction of the neutral wind field, nor on its horizontal gradients. Such affects have been observed previously at other locations around the globe, and their absence at Arecibo may have been due to the limited data set. Thus, we have extended the period of acquisition and analysis of our neutral wind measurements to include nearly three complete solar cycles (or approximately 30 years) and will present our results within the framework of the earlier work. While the earlier conclusion that no major systematic solar cycle influence on the neutral winds at Arecibo generally remains intact, we did find a slight increase in wind magnitude and a gradual, yet consistent rotation of the thermospheric neutral wind vector from a general southeast to a more eastward flow during 30 years of observation. We explain the magnitude and directional variations in terms of long-term changes in the density and temperature of the upper atmosphere and their possible dissimilar influences on each wind component that appear as a rotation of the neutral wind vector.

Description: Bulk 0.7PbZr 0.52 Ti 0.48 O 3 –0.3NiFe 2 O 4 nanoceramic composites with a grain size of ~50 nm were fabricated using chemical synthesis, high-energy ball-milling, and spark plasma sintering. The composite produced broad dielectric constant peaks and frequency dispersion, similar to relaxor ferroelectrics, and was ferroelectric and ferromagnetic. The dielectric and piezoelectric properties of nanoceramics are lower than those of microceramics due to grain-size effects. “Butterfly”-type magnetoelectric (ME) loops indicate that direct stress coupling between magnetostrictive and piezoelectric phases is still active in composite ceramics when the grain size is ~50 nm.

Description: The room temperature onset plastic deformation and crack behavior of 3C-SiC under contact load were investigated using nanoindentation and transmission electron microscopy (TEM). During loading, abrupt bursts or pop-in in the load–displacement curves was observed at a depth of ~60 nm. The 3C-SiC deforms elastically before the pop-in depth, but exhibits a plastic-elastic behavior after that. TEM observations reveal that the shear slip is the predominant deformation mechanism in 3C-SiC during indentation. The cracks usually initiate at the intersection of shear bands or grain boundary. In addition, theoretical analysis confirms that the pop-in event is associated with the onset plasticity of 3C-SiC.

Description: The crack growth resistance behavior of single crystal and polycrystalline 0.71Pb(Mg 1/3 Nb 2/3 )O 3 -0.29PbTiO 3 (PMN-29%PT) was determined with compact-tension specimens. Two different single crystal orientations were produced by the solid-state crystal growth technique (SSCG) and characterized, allowing for the direct comparison to polycrystalline material. Single crystal R -curve behavior was observed to be anisotropic, which is explained by the effects of ferroelasticity and stress-induced phase transformations on toughening. Results of the polycrystalline samples display comparable toughness to that observed in single crystal measurements.

Description: Cold point mesopause is characterized by the coldest point in the temperature profile of the Earth's atmosphere. TIMED/SABER observations of cold point mesopause and its variability at diurnal and planetary wave scales are discussed in this study. For the first time, the diurnal and semidiurnal tidal modulations of mesopause are quantified on a global scale during all the four seasons, namely, winter, vernal equinox, summer, and autumnal equinox. The composite of diurnal variations of mesopause height and temperature are discussed during each season and using least squares fit, diurnal and semidiurnal tidal amplitudes and phases are obtained. Most of the features exhibited by the diurnal variation of mesopause height are consistent with the present understanding of the migrating tides. The diurnal tidal modulations of mesopause show its peak over equatorial latitude and change its phase around 20° latitude. The phase of the diurnal tidal modulation is consistent during all seasons expect for a phase shift of 4–6 h observed during boreal summer. The similarities/discrepancies between the latitudinal structure of migrating tides and the diurnal variation of mesopause height are discussed. The results reveal that the diurnal tidal modulations of mesopause height show hemispherical asymmetry, which is not reflected in mesopause temperature. The diurnal and semidiurnal amplitudes in mesopause height across the globe are comparable in magnitude and it is found that over equatorial and low latitudes, the variability of mesopause is maximum at these scales as compared to seasonal scales. Quantification of mesopause height at diurnal scales is very important as it also changes the chemistry of that region. In the present study, an attempt is also made to demonstrate the modulation of the mesopause by propagating planetary waves. The results emphatically show that propagating planetary waves do modulate the mesopause height.

Description: The certification of a boron carbide reference material for chemical composition is described. The mass fractions of 16 elements and two boron species are certified in an international interlaboratory comparison with 35 participating laboratories from six different countries. Beside chemical characterization the certification process includes homogeneity and stability testing of the candidate material boron carbide (type F360, 305M422). Details of the analytical methods used for chemical characterization and of the calculation of the uncertainties of the certified mass fractions are given. The new reference material ERM ® -ED102 with certified mass fractions of 18 parameters (elements and species) and of the amount fraction of the isotope 10 B is a valuable tool for laboratories working in the field of advanced ceramic materials analysis to improve their analytical results.

Description: The thermoelectric properties of the fluorite-related oxide, In 4 Sn 3 O 12 , have been investigated by studying the system In 4− x Ga x Sn 3 O 12 , with 0 ≤  x  ≤   0.15. It has been shown that Ga does not enter the In 4 Sn 3 O 12 matrix, and two secondary phases form via the Ga introduction: SnO 2 and Ga 2 In 6 Sn 2 O 16 . By reactive sintering between In 2 O 3 , SnO 2 , and Ga 2 O 3 precursors, the density of the samples is considerably increased from 66% (actual density/theoretical density) for x  =   0 up to 90% for x  =   0.15, which significantly decreases the electrical resistivity. This is attributed to the large number of grain boundaries localized among the secondary phases, which inhibit the grain growth and hence favor the densification. The phase In 4 Sn 3 O 12 is for the first time reported to exhibit a semi-metallic behavior. The Seebeck coefficient does not change significantly with respect to the pristine matrix in accordance with the fact that Ga does not play any role as a doping agent. The thermal conductivity increases with the Ga content. The maximum figure of merit, ZT  = 0.23, at 1000 K obtained at a very low Ga content ( x  =   0.05), is comparable to the value obtained for Ge doped In 2 O 3 ( ZT  ~ 0.3). This study suggests that In 4 Sn 3 O 12 can be a potential material for thermoelectric applications.

Description: In this work, we report on the temperature-dependent crystal structures of the isostructural, layered hexagonal phases Ti 2 AlN and Cr 2 GeC determined by Rietveld analysis of high temperature neutron powder diffraction data of fully dense, polycrystalline, bulk samples in the 100° to 1100°C temperature range. For both phases, the A-group atoms, Al and Ge, vibrate with the highest amplitude and do so anisotropically within the basal plane. All bonds expand linearly with temperature, with the highest relative thermal expansion occurring in the Ti–Al and Cr–Ge bonds. The thermal expansion coefficients in the a - and c -direction are, respectively, 10.3(±0.2) × 10 −6 and 9.3(±0.2) × 10 −6  K −1 for Ti 2 AlN and 12.8(±0.3) × 10 −6 and 14.6(±0.3) × 10 −6  K −1 for Cr 2 GeC. The unit cell volume expansions observed by HTND are 10.0(±0.2) × 10 −6  K −1 for Ti 2 AlN and 13.4(±0.3) × 10 −6  K −1 for Cr 2 GeC.

Description: We present a study of Spread F occurrence over a location under the southern crest of the equatorial ionization anomaly (Cachoeira Paulista 22.7°S, 45.0°W, mag. Lat.: 16°S, dip angle: −32.3°, Brazil) during the last solar cycle, which presented an extended solar minimum activity. After analyzing hundreds of ionograms obtained with a digital ionosonde DGS 256, between 2001 and 2010, we verified high Spread F occurrence around midnight-postmidnight during June solstice (Southern Hemisphere winter) with a peak occurrence between 2006 and 2009, when the solar flux has reached very low values (

Description: In this paper we examine suprathermal He ions measured by the Suprathermal Ion Telescope instrument associated with tilted corotating interaction regions (CIRs). We use observations of the two STEREO spacecraft (S/C) for the first 2.7 years of the mission, along with ground-based measurements of the solar magnetic field during the unusually long minimum of Solar Cycle 23. Owing to the unique configuration of the STEREO S/C orbits, we are able to investigate spatial variations in the intensity of the corotating ions on time scales of less than one solar rotation. The observations reveal that the occurrence of the strong CIR events was the most frequent at the beginning of the period. The inclination of the heliospheric current sheet relative to the heliographic equator (the tilt angle) was quite high in the first stage of the mission and gradually flattened with the time, followed by a decrease in the CIR activity. By examining the differences between measurements on the two STEREO S/C, we discuss how the changes in the position of the S/C relative to the CIRs affect the energetic particle observations. We combine STEREO observations with observations from the Ultra Low Energy Isotope Spectrometer (ULEIS) instrument on the ACE S/C and argue that the main factor that controls the differences in the ion intensities is the latitudinal separation between the two STEREO S/C relative to the tilted CIRs. The position of the S/C is less important when the tilt angle is high. In this case we found that the CIR ion intensity positively correlates with the tilt angle.

Description: The spatiotemporal evolution of the daytime mesopause temperature (MT) over a tropical station, Trivandrum (8.5°N, 77°E), has been investigated during the annular solar eclipse of 15 January 2010 using a meridional scanning Multi-Wavelength Dayglow Photometer. This eclipse was a unique event by virtue of its exceptionally long duration and noontime occurrence over the present observational site. It has been observed that during the course of the eclipse, MT underwent significant enhancement (∼35 K). This increase in temperature was found to be present throughout the region of coverage of the photometer, i.e., ±200 km centered at Trivandrum in the meridional direction. It has also been found that the enhancement in MT revealed a preferential northward/southward movement before/after the main phase of the eclipse. In addition to this, a sudden launch of gravity waves with periodicity of ∼30 min was noticed during the first contact, which was amplified during the maximum phase of the eclipse. Another noteworthy observation was the amplification of a ∼2 hour wave during the course of the eclipse. These observations and their plausible mechanisms are discussed in detail in context of the daytime hydroxyl emissions and mesopause energetics and dynamics.

Description: Ground-based Global Positioning System (GPS) measurements of ionospheric total electron content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the Samoa earthquake of 29 September 2009 and the Chile earthquake of 27 February 2010. Both earthquakes produced ocean tsunamis that were destructive to coastal communities near the epicenters, and both were observed in tidal gauge and buoy measurements throughout the Pacific Ocean. We observe fluctuations in TEC correlated in time, space, and wave properties with these tsunamis using the Jet Propulsion Laboratory's Global Ionospheric Mapping software. These TEC measurements were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range for tsunamis. Observable variations in TEC appear correlated with the tsunamis in some locations (Hawaii and Japan), but not in others (Southern California or near the epicenters). Where variations are observed, the typical amplitude tends to be ∼0.1–0.2 TEC units for these events, on the order of ∼1% of the background TEC value. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupled model, and are found to be in good agreement. Significant TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed coincided with clear TEC observations, while a lack of clear TEC observations coincided with smaller sea surface height amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

Description: Multipoint spacecraft observations provide unique opportunities to constrain the propagation and evolution of interplanetary coronal mass ejections (ICMEs) throughout the heliosphere. Using Mars Global Surveyor (MGS) data to study both ICME and solar energetic particle (SEP) events at Mars and OMNI and Geostationary Operational Environmental Satellite (GOES) data to study ICMEs and SEPs at Earth, we present a detailed study of three CMEs and flares in late November 2001. In this period, Mars trailed Earth by 56° solar longitude so that the two planets occupied interplanetary magnetic field lines separated by only ∼25°. We model the interplanetary propagation of CME events using the ENLIL version 2.6 3-D MHD code coupled with the Wang-Sheeley-Arge version 1.6 potential source surface model, using Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) images to determine CME input parameters. We find that multipoint observations are essential to constrain the simulations of ICME propagation, as two very different ICMEs may look very similar in only one observational location. The direction and width of the CME as parameters essential to a correct estimation of arrival time and amplitude of the ICME signal. We find that these are problematic to extract from the analysis of SOHO/LASCO images commonly used for input to ICME propagation models. We further confirm that MGS magnetometer and electron reflectometer data can be used to study not only ICME events but also SEP events at Mars, with good results providing a consistent picture of the events when combined with near-Earth data.

Description: We have extended our earlier calculations of the distance to the heliospheric termination shock (HTS), which covered the period from the launch of V1 and V2 in 1977 to 2005, to the period from 2006 to 2011. During this latter period, the solar wind speed, ram pressure, and magnetic field decreased to the lowest levels in recent history, related to the sunspot minimum in 2008–2009. The HTS distance has decreased correspondingly so that V1, which was crossed by the HTS at 94 AU in late 2004, would now, in early 2011, be expected to reach the HTS at a distance of ∼80 AU, when the HTS distance would be expected to be at its minimum. Similarly, V2, which was crossed by the HTS at 84 AU in mid-2007, would, in early 2011, reach the HTS at a distance of only 74 AU. These distances, in early 2011, are ∼15% less than those at which V1 and V2 initially reached the HTS. The distance to the heliopause (HP) is more uncertain, but recent calculations place its equilibrium distance at between 1.4 and 1.6 times the HTS distance. Allowing for an additional 1 year for the HP to reach its equilibrium minimum distance relative to the HTS would mean that, assuming this distance remains a constant fraction larger than the HTS distance, the HP distance would be at its minimum distance of (1.4–1.6) × 80 AU = 112–128 AU at V1 in early 2012. At this time, V1 will be in the direction of a distance of ∼120 AU so that there is a possibility that V1 could cross the HP and enter interstellar space at the time 2012.0 ± 1 year. If the crossing does not happen during this time period, then it is unlikely that V1 will reach this defining boundary before about 2016 because of the expected outward motion of the HTS and the HP toward their more normal distances of 85–96 and ∼120–140 AU, coincident with the maximum of the new sunspot cycle.

Description: We have analyzed Cluster magnetic field and plasma data during high-altitude cusp crossing on 14 February 2003. Cluster encountered a diamagnetic cavity (DMC) during northward interplanetary magnetic field (IMF) conditions, and as IMF rotated southward, the spacecraft reencountered the cavity more at the sunward side. The DMC is characterized by a high level of magnetic field fluctuations and high-energy electrons and protons. Ultralow-frequency turbulence has been suggested as a mechanism to accelerate particles in DMC. We demonstrate in this paper for the first time that many of the low-frequency fluctuations in the cavity are back and forth motion of the DMC boundaries over the spacecraft and transient reconnection signatures. We also find examples of some isolated high-amplitude waves that could possibly be nonlinear kinetic magnetosonic modes. The lack of strong wave power at the vicinity of local ion cyclotron frequency in the DMC suggests that perhaps a mechanism other than wave-particle heating is a dominant source for ion heating in DMCs.

Description: Knowledge of multidimensional correlation functions is crucial for understanding the anisotropy of turbulence. The two-dimensional (2-D) spatial correlation functions (SCFs) obtained in previous studies of space plasma turbulence were restricted to large-length scales and covered a limited angular domain of the two-point separation vector with respect to the mean magnetic field. Here we aim to derive 2-D SCFs with smaller-length scale and nearly full angular distribution for the fluctuations of the number density and magnetic field in magnetosheath turbulence. We use the Cluster four-spacecraft measurements of the fluctuations with respect to a temporally and spatially varying background magnetic field to construct the 2-D SCFs. We find that the correlation function of the density fluctuations shows a pattern similar to that of the magnetic field fluctuations, both of which appear to be composed of two populations, whereby the major population extends along the coordinate parallel to mean magnetic field (S$\parallel$) and the minor one deviates toward the perpendicular coordinate (S$\perp$). This pattern of 2-D SCFs implies that the energy of magnetosheath turbulence seems to cascade, in the inertial range close to the ion scale, mostly transverse to the background magnetic field and meanwhile partly along the field (i.e., k$\perp$ $\gg$ k$\parallel$).

Description: Modulation of whistler mode chorus waves, which plays an important role in driving the pulsating aurora and other processes related to energetic electron dynamics, is an interesting but a long-standing unresolved problem. Here we utilize in situ observations from the THEMIS spacecraft to investigate the role of density variations in the modulation of the chorus wave amplitude, which forms a complementary study to the modulation of chorus by compressional Pc4–5 pulsations presented in a companion paper. We show that these density variations are correlated remarkably well with modulated chorus intensity and typically occur on a timescale of a few seconds to tens of seconds. Both density depletions (DD) and density enhancements (DE) are frequently correlated with increases in chorus wave amplitudes. Furthermore, density enhancements cause a lowering of the central frequencies of the generated chorus waves and vice versa. DD events are more likely to be related to quasi-periodic chorus emissions and thus may be related to the generation of the pulsating aurora. A systematic survey of both DD and DE events shows that DD events preferentially occur between premidnight and dawn, whereas DE events dominantly occur from dawn to noon. We also evaluate the growth rates of chorus waves using linear theory for both DD and DE events and show that both density depletions and enhancements can lead to an intensification of chorus wave growth. However, other potential mechanisms for chorus intensification caused by density variations such as wave trapping by density crests and troughs cannot be excluded.

Description: High surface area BiFeO 3 thin films were deposited on ITO substrates by templates method and chemical solution deposition. The resulting phase composition and microstructures were characterized using X-ray diffraction, scanning electron microscopy and Raman spectroscopy. We further demonstrated the useful photocatalytic activity of these films as determined by degradation of Congo red under visible-light irradiation ( λ 〉 400 nm). Our results showed that the surface area have a great effect on the photocatalytic performances of the BiFeO 3 thin films.

Description: We have developed a novel ion conductor comprising magnesium hafnium tungstate (MgHf(WO 4 ) 3 ) as a solid electrolyte for future metal-air batteries. The conductivity of this material measured as 2.5 × 10 −4 S/cm at 600°C is about one order of magnitude higher than that of existing ion conductor with similar structure, such as Sc 2 (WO 4 ) 3 . We have also elucidated for the first time that MgHf(WO 4 ) 3 has an intrinsic crystal structure, forming one-dimensional (1-D) alignments of individual Mg 2+ and Hf 4+ ions alternating within quasi-layered WO 4 2– units at Sc 3+ sites in Sc 2 (WO 4 ) 3 . The structure observed by HAADF-STEM clearly coincides with the results obtained by first principle calculation. The mechanism for high ion conductivity is discussed from the viewpoints of its ordered structure and physical property of negative thermal expansion.

Description: In the present work, compaction, sintering behavior, and mechanical properties of Al 2 O 3 –CeO 2 composite nanopowders were investigated. Al 2 O 3 and Al 2 O 3 –CeO 2 composite nanopowders were prepared by a sol–gel method. The effect of CeO 2 on compressibility, sintering rate, final density, and mechanical properties was studied. The aggregation strength of nanopowders reduced from 158 to 101 MPa by adding 5 wt% CeO 2 . The amount of CeO 2 had a strong effect on the sintering behavior and final microstructure of nanopowders and it inhibited alumina grain growth and suppressed densification process. The activation energy for grain growth increased from 428 to 554 kJ/mol by adding 5 wt% CeO 2 to the nanopowders. The addition of 5 wt% CeO 2 improved fracture toughness (by 28%) and flexural strength (by 17%) with respect to monolithic Al 2 O 3 .

Description: ELF/VLF waves have been generated via steerable HF heating of the lower ionosphere. The temperature-dependent conductivity of the lower ionospheric plasma enables HF heating (and subsequent recovery) to modulate natural current systems such as the auroral electrojet, thus generating an antenna embedded in the ionospheric plasma. We apply a realistic three-dimensional model of HF heating and ionospheric recovery, as well as ELF/VLF wave propagation in and below the ionosphere, to derive the radiation pattern into the magnetosphere as a result of steerable HF heating. It is found that modulated HF heating preferentially directs signals upward into space because of the phasing effect of the upward HF wave propagation. We find that the steering techniques such as the geometric modulation “circle sweep” enhances the total ELF/VLF power injected into the magnetosphere by 5–7 dB compared to amplitude modulated heating, with a few dB enhancement in the peak magnetic field value. Another technique known as beam painting enhances the total injected power by 1–3 dB but produces weaker peak magnetic fields due to the power being spread over a larger area. Observations on the DEMETER spacecraft are presented and compared with theoretical predictions. DEMETER observations show that the signal produced with geometric modulation can be stronger than the signal from AM under the same conditions.

Description: For nearly a century it has been known that the tendency for geomagnetic activity is, on average, higher at the equinoxes than at the solstices. Previous studies on semiannual geomagnetic activity were performed mainly for geomagnetic indices such as am, aa, U, and AL. Thus, we need to understand the seasonal variation of geomagnetic activity defined by the Dst index over the long term. It is also necessary to test the solar magnetic polarity dependence of geomagnetic activity. This paper is a statistical analysis of the geomagnetic storms defined by the Dst index. Our storm data consists of two sets of storm data for 5 years at each solar minimum during the four solar cycles (19–22) from 1962 through 1998 for two of each solar magnetic polarity. The storms are divided into two groups defined by Dst index (Dst(min) 〈 −50 nT, ∣Dst∣ 〉 70 nT; Dst(min) 〈 −50 nT, ∣Dst∣ 〉 90 nT). Monthly occurrences of these storms are compared. Storms of ∣Dst∣ 〉 90 nT and of ∣Dst∣ 〉 70 nT occurred 153 and 238 times, respectively, during the testing periods. Storms occurred more frequently during the spring and fall seasons for all solar cycle minima, regardless of solar magnetic polarity.

Description: A widely accepted explanation of the location of the inner edge of the electron plasma sheet and its dependence on electron energy is based on drift motions of individual particles. The boundary is identified as the separatrix between drift trajectories linking the tail to the dayside magnetopause (open paths) and trajectories closed around the Earth. A statistical study of the inner edge of the electron plasma sheet using THEMIS Electrostatic Analyzer plasma data from November 2007 to April 2009 enabled us to examine this model. Using a dipole magnetic field and a Volland-Stern electric field with shielding, we find that a steady state drift boundary model represents the average location of the electron plasma sheet boundary and reflects its variation with the solar wind electric field in the local time region between 21:00 and 06:00, except at high activity levels. However, the model does not reproduce the observed energy dispersion of the boundaries. We have also used the location of the inner edge of the electron plasma sheet to parameterize the potential drop of the tail convection electric field as a function of solar wind electric field (Esw) and geomagnetic activity. The range of Esw examined is small because the data were acquired near solar minimum. For the range of values tested (meaningful statistics only for Esw 〈 2 mV/m), reasonably good agreement is found between the potential drop of the tail convection electric field inferred from the location of the inner edge and the polar cap potential drop calculated from the model of Boyle et al. (1997).

Description: An earthquake of magnitude 9.0 occurred near the east coast of Honshu (Tohoku area), Japan, producing overwhelming Earth surface motions and inducing devastating tsunamis, which then traveled into the ionosphere and significantly disturbed the electron density within it (hereafter referred to as seismotraveling ionospheric disturbances (STIDs)). The total electron content (TEC) derived from nationwide GPS receiving networks in Japan and Taiwan is employed to monitor STIDs triggered by seismic and tsunami waves of the Tohoku earthquake. The STIDs first appear as a disk-shaped TEC increase about 7 min after the earthquake occurrence centered at about 200 km east of the epicenter, near the west edge of the Japan Trench. Fast propagating disturbances related to Rayleigh waves quickly travel away from the epicenter along the main island of Japan with a speed of 2.3–3.3 km/s, accompanied by sequences of concentric circular TEC wavefronts and followed by circular ripples (close to a tsunami speed of about 720–800 km/h) that travel away from the STID center. These are the most remarkable STIDs ever observed where signatures of Rayleigh waves, tsunami waves, etc., simultaneously appear in the ionosphere.

Description: The specific entropy (entropy density) S is examined for the outer electron radiation belt at geosynchronous orbit and for the energetic electron population in the Earth's magnetotail. The outer electron radiation belt is measured with the SOPA detectors on board six geosynchronous satellites and the energetic electrons of the magnetotail are measured with instrumentation on board 12 Global Positioning Satellites (GPS) with a magnetic field model used to map the GPS orbit to the magnetotail. Density n and temperature T values are determined from relativistic Maxwellian fits to the electron measurements, enabling the specific entropy S to be calculated. For low temperatures the nonrelativstic specific entropy is S = T/n2/3; for a relativistic Maxwellian distribution a relativistically correct expression for S = S(T,n) is derived and used. The outer electron radiation belt at geosynchronous orbit local midnight (n ∼ 3 × 10−4 cm−3 and T ∼ 140 keV) and the energetic-electron population in the magnetotail (n ∼ 1 × 10−4 cm−3 and T ∼ 50 keV) statistically have the same specific entropy. Hence the two populations are probably the same. This implies adiabatic transport (1) from the magnetotail to the dipole (where the magnetotail electrons are the source of the outer electron radiation belt) or (2) from the dipole to the magnetotail (where the magnetotail electrons are leakage from the radiation belt).

Description: Solar wind dynamic pressure (Pdyn) enhancements have been observed to cause large-scale auroral brightening. The mechanism for this kind of auroral brightening is still a topic of current space research. Using the global piecewise parabolic method Lagrangian remap (PPMLR)-MHD simulation model, we investigate three auroral brightening events caused by dynamic pressure enhancement under different interplanetary magnetic field (IMF) conditions: (1) Bz 〈 0 and By 〉 0 on 11 August 2000, (2) Bz 〈 0 and By 〈 0 on 8 May 2001, and (3) Bz ≥ 0 on 21 January 2005. We show that the auroral location depends on the IMF conditions. Under southward IMF conditions, when By is negative, the duskside aurora is located more equatorward at around 70° magnetic latitude (MLAT) for all magnetic local times; when By is positive, the duskside aurora can even reach beyond 80° MLAT. A smaller and more localized response is seen when the IMF Bz is nearly zero or northward, as shown in previous studies. Our simulation results are consistent with these observations, indicating that the observed aurora activities could be caused by solar wind dynamic pressure enhancements. The simulation results suggest that the enhancement of Pdyn can increase the ionospheric transpolar potential and the corresponding field-aligned currents, leading to the observed auroral brightening.

Description: On 18 February 2003 a long-duration, almost monochromatic, wave event was detected by Cluster at radial distances from the bow shock smaller than ≈10 Re. The interplanetary magnetic field orientation determined a wide and almost symmetric foreshock region around the bow shock nose, providing highly favorable conditions for a direct wave penetration into the magnetosphere. The general correspondence between the characteristics of the wave trains observed in the foreshock region and at two widely separated ground stations (namely, at low latitudes in the Northern Hemisphere and in Antarctica) confirms that the ground activity is ubiquitously determined and controlled by the upstream activity. At low latitudes, the direct propagation of the external waves through the subsolar point is sharply confined to the dayside hemisphere. In Antarctica, the wave activity is detected even on field lines stretched into the tail; here the polarization pattern suggests a significant contribution of sunward propagating waves in the postmidnight hours, consistent with a wave penetration through the magnetotail lobes. At both stations the wave energy is typically ≈5–10% of the external energy; in addition, in Antarctica the contribution of the cusp turbulence largely overcomes that one related to the penetration of the upstream waves.

Description: A 400-nm-thick (Pb 0.97 La 0.02 )(Zr 0.97 Ti 0.03 )O 3 (PLZT 2/97/3) antiferroelectric (AFE) thin films with different lead excess content (0%, 10%, and 20%) were successfully deposited on Pt(111)/TiO 2 /SiO 2 /Si substrates via a sol–gel process. The effects of lead excess content on the microstructure, dielectric properties, and energy storage performance of PLZT 2/97/3 AFE thin films were investigated in details. X-ray diffraction results displayed that AFE thin films were changed from the (111)-preferred orientation to the (100) and (111)-mixed orientation with increasing lead excess content. Dielectric measurements showed that AFE thin films with higher lead excess content exhibited enhanced dielectric constant and larger phase transformation fields. Thus, the energy storage density of AFE thin films was also remarkably improved from 3.3 to 11.7 J/cm 3 at 1200 kV/cm.

Description: In this paper, we investigate the role of plasma sheet bubbles in the ion flux variations at geosynchronous orbit during substorm injections by using the Rice Convection Model with an equilibrated magnetic field model (RCM-E). The bubble is initiated in the near-Earth plasma sheet with a localized reduction in entropy parameter PV5/3 following a substorm growth phase. In the expansion phase, characteristic features of substorm injections are reproduced; that is, there is a prominent dispersionless flux increase for energetic protons (〉40 keV) and a flux decrease for lower-energy protons near midnight geosynchronous orbit while there is dispersive flux enhancement near the dusk sector. We find that the injection boundary is well coincident with the earthward boundary of the bubble, inside which the depletion of plasma content causes the magnetic field dipolarization, and in return, the magnetic field collapse energizes particles and alters the drift paths dramatically. Our results also show that a high-PV5/3 island is pushed ahead of the fast earthward propagating bubble, and a dipolarization front forms between them. Within the high-PV5/3 island, the diamagnetic effect makes the plasma pressure increase and the strength of the magnetic field decrease to a local minimum. We suggest that plasma sheet bubbles are elementary vehicles of substorm time particle injections from the main plasma sheet to the inner magnetosphere.

Description: The thermospheric response at satellite altitudes along low Earth orbit is subject to the energy deposition locally, i.e., at high altitudes, and the vertical wave propagation from the energy injection at lower altitudes. In this study, a general circulation model has been run to investigate the source of nonhydrostatic effects and the sensitivity of the vertical wind and neutral density at satellite orbits to the energy deposited at low and high altitudes. Through comparing the simulations with and without the Joule heating enhancement above 150 km altitude, the impact of the heating at low and high altitudes on the high-altitude thermosphere has been separated. The numerical simulations show that most of the nonhydrostatic effects at high altitudes (300 km) arise from sources below 150 km and propagate vertically through the acoustic wave. The heating above 150 km is responsible for a large increase of the average vertical velocity (40 m/s) and neutral density (50%) at 300 km and higher altitudes.

Description: We have developed a numerical model of a double-probe electric field sensor equipped with a photoelectron guard electrode for the particle-in-cell simulation. The model includes typical elements of modern double-probe sensors on, e.g., BepiColombo/MMO, Cluster, and THEMIS spacecraft, such as a conducting boom and a preamplifier housing called a puck. The puck is also used for the guard electrode, and its potential is negatively biased by reference to the floating spacecraft potential. We apply the proposed model to an analysis of an equilibrium plasma environment around the sensor by assuming that the sun illuminates the spacecraft from the direction perpendicular to the sensor deployment axis. As a simulation result, it is confirmed that a substantial number of spacecraft-originating photoelectrons are once emitted sunward and then fall onto the puck and sensing element positions. In order to effectively repel such photoelectrons coming from the sun direction, a potential hump for electrons, i.e., a negative potential region, should be created in a plasma region around the sunlit side of the guard electrode surface. The simulation results reveal the significance of the guard electrode potential being not only lower than the spacecraft body but also lower than the background plasma potential of the region surrounding the puck and the sensing element. One solution for realizing such an operational condition is to bias the guard potential negatively by reference to the sensor potential because the sensor is usually operated nearly at the background plasma potential.

Description: In a recent observation by the Cluster spacecraft, emissions triggered by electromagnetic ion cyclotron (EMIC) waves were discovered in the inner magnetosphere. We perform hybrid simulations to reproduce the EMIC triggered emissions. We develop a self-consistent one-dimensional hybrid code with a cylindrical geometry of the background magnetic field. We assume a parabolic magnetic field to model the dipole magnetic field in the equatorial region of the inner magnetosphere. Triggering EMIC waves are driven by a left-handed polarized external current assumed at the magnetic equator in the simulation model. Cold proton, helium, and oxygen ions, which form branches of the dispersion relation of the EMIC waves, are uniformly distributed in the simulation space. Energetic protons with a loss cone distribution function are also assumed as resonant particles. We reproduce rising tone emissions in the simulation space, finding a good agreement with the nonlinear wave growth theory. In the energetic proton velocity distribution we find formation of a proton hole, which is assumed in the nonlinear wave growth theory. A substantial amount of the energetic protons are scattered into the loss cone, while some of the resonant protons are accelerated to higher pitch angles, forming a pancake velocity distribution.

Description: We analyze the heliocentric evolution of fast interplanetary counterparts of coronal mass ejections (ICMEs) and their transient shocks to investigate how and where they decelerate in the interplanetary medium. We employ two one-dimensional hydrodynamic models, analytic and numeric, to study three fast CME events. We focus on the transferring of momentum from the ICME to the shock. The two models show that initially the fast ICME propagates at about a constant speed and drives the shock (driving stage) until it reaches a certain distance from which it decelerates and decouples from the shock (decoupling process). Then the ICME and its shock decelerate (decaying stage). This deceleration depends on the speed difference with respect to the ambient wind and tends to a negligible value when the ICME-shock approaches to the ambient wind speed. The location and duration of these propagation stages depend on the initial CME conditions and the ambient wind characteristics. We present a parametric study to compare the results by the analytic and numeric models, showing the variations of their results as a function of the initial conditions. We perform three study cases to compare the model's predictions with a set of speed measurements of ICME-shock events.

Description: We discuss results of a superposed epoch analysis of dipolarization fronts, rapid (δt 〈 30 s), high-amplitude (δBz 〉 10 nT) increases in the northward magnetic field component, observed during six Time History of Events and Macroscale Interactions during Substorms (THEMIS) conjunction events. All six fronts propagated earthward; time delays at multiple probes were used to determine their propagation velocity. We define typical magnetic and electric field and plasma parameter variations during dipolarization front crossings and estimate their characteristic gradient scales. The study reveals (1) a rapid 50% decrease in plasma density and ion pressure, (2) a factor of 2–3 increase in high-energy (30–200 keV) electron flux and electron temperature, and (3) transient enhancements of ∼5 mV/m in duskward and earthward electric field components. Gradient scales of magnetic field, plasma density, and particle flux were found to be comparable to the ion thermal gyroradius. Current densities associated with the Bz increase are, on average, 20 nA/m2, 5–7 times larger than the current density in the cross-tail current sheet. Because j · E 〉 0, the dipolarization fronts are kinetic-scale dissipative regions with Joule heating rates of 10% of the total bursty bulk flow energy.

Description: The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io's orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io's was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models.

Description: The equatorial mass density anomaly (EMA) is a fascinating phenomenon in the equatorial upper atmosphere. In this study, we investigate the generation mechanism of the EMA using the ground-to-topside model of the atmosphere and ionosphere for aeronomy (GAIA). The GAIA model is a self-consistent global model of the atmosphere and ionosphere covering the height range from the ground surface to the exobase. It can reproduce the observed EMA structure at 300–400 km heights. Our results show that the EMA structure can extend down to 200 km height. The EMA during daytime is caused by the in situ diurnal tide and the upward propagating terdiurnal tide. About half of the magnitude of the EMA is generated by the upward propagating terdiurnal tide from the lower atmosphere. This is the first report concerning the importance of the upward propagating tide for EMA formation. The in situ diurnal tide in the thermosphere is also essential for EMA formation. The in situ diurnal tide is modified by the momentum exchange between the plasma and the neutral atmosphere. This is seen as the enhanced upward flow of the neutral atmosphere along the dip equator in the 200–400 km height region, which has a profound effect on the latitudinal distributions of the atmospheric composition, temperature, pressure, and density in the thermosphere.

Description: Porous Si 3 N 4 ceramics with interconnected pores were fabricated by the phase separation method using benzoic acid (BA) as a pore-forming agent. The green bodies were prepared at room temperature under vacuum and pore-forming agent was quickly removed by sublimation below 200°C. The resulting porous green body exhibits uniform distribution of rod-like pores in the matrix. The porosity can be controlled by adjusting the BA content in Si 3 N 4 slurry. The flexural strength and fracture toughness of the porous Si 3 N 4 samples are in the range of 85–126 MPa and 1.08–1.7 MPa·m 1/2 with the porosity range of 57%–65.8%.

Description: In this work, we have prepared copper-doped multicomponent tellurite glasses by solid state electric field-assisted diffusion. The concentration profiles of the elements have been measured by the secondary ion mass spectrometry. The depth profile of copper can be well fitted only by a modified erfc-like solution of the second Fick's law which assumes that both the Cu + and Cu 2+ ions are involved in the diffusion. The modeling shows that the Cu 2+ ions are much more mobile than the Cu + ones in the tellurite glasses and affected strongly by the applied electric field. Our results demonstrate the possibility of fabricating copper-doped planar waveguides based on the tellurite glasses.

Description: By a self-organization process of alginate sol, alumina ceramic bodies with high porosity characterized by highly ordered and unidirectional oriented pores in the micrometer range were successfully fabricated with a 5–15 wt% solid loading range. The obtained porous Al 2 O 3 ceramics had a high total porosity over 70%, most (〉88%) of which were open pores, as well as an excellent permeability (K 〉 2.16 × 10 −11 m 2 ) and high compressive strength (〉15 MPa). The pore size, porosity, and thus the permeability and mechanical properties of the sintered ceramics can be effectively controlled by choosing different initial solid loadings.

Description: Networked ZnO nanowire sensors have been fabricated via selective growth of ZnO nanowires by the vapor growth method. The number of junctions per electrode pair (NJE) was deliberately controlled by changing the spacing of interdigital electrodes. Its effects on the sensing properties to NO 2 and CO were investigated. As the NJE increased, superior sensing properties were attained. This novel method to fabricate gas sensors using vapor-phase grown nanowires may circumvent the drawbacks of single nanowire gas sensors. Importantly, the NJE needs to be tuned to fully exploit networked nanowires in gas sensors.

Description: Perovskite Ba 0.6 Sr 0.4 TiO 3 (BST), pyrochlore Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN), and hetero layered BZN/BST films have been directly grown on high resistivity (HR)-Si substrates by radio frequency magnetron sputtering. The microwave properties (up to 50 GHz) of all the films are evaluated by fabricating coplanar waveguide configuration. Experimental results showed that the BZN layer helped in tailoring the dielectric constant and reducing the loss tangent significantly. Moreover, the resulting BZN/BST/HR-Si films show moderate permittivity (~258) and tunability (~15.63%, 200 kV/cm), and low microwave loss (~0.0175) at 2 GHz and their microwave properties (1–50 GHz) potentially could be made suitable for integrated microwave tunable devices.

Description: Interaction between modified (K,Na)NbO 3 ceramics and metallic silver has been experimentally studied to simulate effects of using Ag-containing electrode pastes in multilayer actuators with alkali-based ferroelectric layers. The solubility limit of silver added as an excess component is found to vary in the range of 0.8–2.5 mol% depending on composition and stoichiometry of the ceramics. Inhomogeneous distribution of the residual undissolved silver across the thickness of a single ceramic layer between the co-fired Ag–Pd electrodes is evidenced by X-ray diffraction. The overall effect of Ag as excess component on temperature of the orthorhombic–tetragonal phase transition is found different from the known effect of Ag as alkali substituent.

Description: A test particle simulation has been performed in order to reproduce the interaction between protons and time-dependent electromagnetic fluctuations in the magnetotail current sheet. The three-dimensional model takes into account a dawn-dusk electric field component E0y, a magnetic field reversal Bx(z), and a constant component Bn along the z direction. Electromagnetic perturbations are generated by random oscillating “clouds” moving in the (x, y) plane. The simultaneous presence of stochastic time-dependent fluctuations and 3-D large-scale fields gives rise to a rich variety of phenomena that are studied by varying the size and shape of the oscillating clouds. The main findings are as follows: (1) the efficiency of the Fermi-like interaction between test particles and moving clouds is largest close to z = 0, where the large-scale magnetic field is weakest; (2) in times of 1–2 min protons can reach energy values up to 50–70 keV, which is beyond the maximum potential drop due to the presence of E0y; (3) the ion energization grows with the size of the magnetic clouds, while it is slightly influenced by the thickness of the clouds along z, confirming that the main acceleration takes place in the quasi-neutral sheet; and (4) assuming parameters of the model corresponding to those of the Earth's magnetotail, it is found that many observed features, such as the formation of a beam in velocity space and non-Gaussian velocity distributions, can be reproduced.

Description: In this paper we present the global spatial structure and seasonal variability of the COSMIC electron density response to the forced from below DE3 and DE2 tides during the period January 2008 to March 2009. The COSMIC electron density at fixed altitudes and SABER temperatures were utilized in order to define the ionospheric DE3 and DE2 tidal response to the DE3 and DE2 temperature tides coming from below. The tidal waves from both data sets have been extracted by the same data analysis method. The latitude structure of the ionospheric response for heights up to 450–500 km is distributed on both sides of the dip equator at about ±30° modified dip latitude; above 500 km the response is approximately confined over the equator. Two altitude regions of enhanced ionospheric response are found: an upper level response (above 300 km) and a bottom level one (below 250 km); the two regions are separated by a narrow altitude zone with no tidal response. The different phase structure of the ionospheric response in both altitude regions suggests that (1) the upper level response is mainly due to the DE3/DE2 modulated vertical plasma drift and (2) the bottom level response is complex and, in all likelihood, is caused by more than one mechanism.

Description: The inversion algorithm for Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE) has been created to gain insight into ionospheric dynamics, particularly when direct measurement is unavailable. We extend the capabilities of EMPIRE here, in order to demonstrate its effectiveness on densities obtained from real data. We apply this method to real Ionospheric Data-Assimilation 4-Dimensional (IDA4D) data from storm time measurements, focusing on the midlatitude F2 layer. EMPIRE is used to estimate midlatitude field-aligned and field-perpendicular drifts. The estimated upward drifts from EMPIRE are validated against measurements obtained from the Millstone Hill incoherent scatter radar zenith antenna. The horizontal $\vec {E}$ × $\vec {B}$ drifts are compared to the assimilative mapping of ionospheric electrodynamics (AMIE) model, which estimates drifts from data sources independent of those used in IDA4D. Results show that the direction and magnitude of the $\vec {E}$ × $\vec {B}$ drifts (and therefore the electric fields) may be deduced from imaging based primarily on total electron content data, although altitude variation is not significantly discernible. We also indicate that the initial uplift of the storm-enhanced density may have been more strongly influenced by field-aligned contributions of neutral winds and diffusion than the electric fields.

Description: Long-term observations of proton cyclotron waves in the upstream region of Venus raise the question of under which general solar wind conditions these waves are generated and maintained. The waves are characterized by their occurrence at the local proton cyclotron frequency and left-hand polarization, both in the spacecraft frame. Magnetometer data of the Venus Express spacecraft for two Venus years of observations are analyzed before, during, and after the occurrence of these waves. The configuration of the upstream magnetic field and the solar wind velocity is investigated, to study if the waves are generated from a ring distribution of pickup ions in velocity space or from a parallel pickup ion beam, i.e., for quasi-parallel conditions of solar wind velocity and magnetic field when the solar wind motional electric field is weak. It is found that stable and mainly quasi-parallel magnetic field conditions for up to ∼20 min prior to wave observation are present, enabling sufficient ion pickup and wave growth to obtain observable waves in the magnetometer data. Persistent waves occur mainly under quasi-parallel conditions. This is in agreement with linear theory, which predicts efficient wave growth for instabilities driven by field-aligned planetary ion beams, already for low pickup ion density. The occurrence of highly coherent waves at 4 RV upstream toward the Sun implies that planetary neutral hydrogen is initially picked up at least 5 RV toward the Sun from a sufficiently dense Venus hydrogen exosphere.