Global Observations of the 630-nm Nightglow and Patterns of Brightness Measured by ISUAL

This study investigates the distributions and occurrence mechanisms of the global local-midnight airglow brightness through FORMOSAT-2/ISUAL satellite imaging observations. We focus on the OI 630.0 nm nightglow emission at altitudes of ~250 km along equatorial space. The database used in this study included data from 2007 to 2008 under solar minimum conditions. The data were classified into four specified types in the statistical study. We found that the occurrence of equatorial brightness was often in the vicinity of the geographic equator and mostly at equinoxes with a tendency to move toward the summer hemisphere as the season changes. Conjugate brightness occurring simultaneously on both sides of the geomagnetic equator was observed predominantly in the northern winter. Furthermore, midnight brightness appeared to have lower luminosity from May to July. We suggest that the global midnight brightness associated with the locations and seasons was the result of several effects which include the influence of the thermospheric midnight temperature maximum (MTM), summer-to-winter neutral wind, and ionospheric anomalies

Intensify the application of ZnO-based nanodevices in humid environment: O2/H2 plasma suppressed the spontaneous reaction of amorphous ZnO nanowires

[[abstract]]In this work, we have demonstrated that amorphous ZnO nanobranches (a-ZnO NBs) could spontaneously react from the crystalline ZnO NWs (c-ZnO NWs) at specific humid environment. The spontaneous reaction mechanism and result can be analyzed by humidity controlling and optical microscope (OM)/scanning electron microscope (SEM)/Kelvin probe force microscopy (KPFM)/transmission electron microscopy (TEM) system. We can make the c-ZnO NWs spontaneous reaction happen at different humid environments and suppress the a-ZnO NBs spontaneous reaction by oxygen/hydrogen plasma surface passivation. The hydrogen plasma surface treatment also can improve the UV sensing sensitivity more than twofold. This work provides the mechanism and methods of the a-ZnO NBs spontaneous growth and offers the passivation treatment for strengthening and enhancing ZnO-based nanodevice application in humid environment and UV light detection, respectively.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[ispeerreviewed]]Y[[booktype]]電子版[[booktype]]紙本[[countrycodes]]DE

Recent work on sprite spectrum in Taiwan

campaigns in Taiwan. We first introduce two types of spectroimagers, the slit and slitless types, and discuss their advantages and shortcomings. Next we explore the instrument development and procedures undertaken for this study. In 2006, a slit spectroimager was installed for a sprite campaign and on 15 August of that year, two sprite spectra were recorded using the slit spectroimager along with seven sprites, one halo, one ELVES emission and two jets. By the end of 2015, a slitless spectroimager had been successfully constructed and was ready to conduct additional investigations. On 7 May 2016, a sprite spectrum was recorded using the slitless spectroimager. Following an examination of the calibrations (comprising detection region field of view, wavelength calibration, and response curve), data analysis, and additional calibrations (comprising elevation and azimuthal angles, atmospheric transmittance, and theoretical wavelength calculations) performed in this study, we present the results from our observed sprite spectra using the slit and slitless spectroimagers

Multicolor Photometric Observation of Lightning from Space: Comparison with Radio Measurements

This study evaluates the effectiveness of spectrophotometric measurements from space in revealing properties of lightning flash. The multicolor optical waveform data obtained by FORMOSAT-2/Imager of Sprites and Upper Atmospheric Lightning (ISUAL) were analyzed in relation to National Lightning Detection Network (NLDN), North Alabama Lightning Mapping Array (LMA). As of July 2011, we found six lightning events which were observed by ISUAL and North Alabama LMA. In two of these events, NLDN showed clear positive cloud-to-ground (CG) discharges with peak current of +139.9 kA and +41.6 kA and, around that time, LMA showed continuous intra-cloud (IC) leader activities at 4-6 km altitudes. ISUAL also observed consistent optical waveforms of the IC and CG components and, interestingly, it was found that the blue/red spectral ratio clearly decreased by a factor of 1.5-2.5 at the time of CG discharges. Other four lightning events in which NLDN did not detect any CG discharges were also investigated, but such a feature was not found in any of these cases. These results suggest that the optical color of CG component is more reddish than that of IC component and we explain this as a result of more effective Rayleigh scattering in blue light emissions coming from lower-altitude light source. This finding suggests that spectral measurements could be a new useful technique to characterize ICs and CGs from space. In this talk, we will also present a result from lightning statistical analysis of ISUAL spectrophotometric data and ULF magnetic data

Perturbed angular correlation spectroscopy of oxide ceramics at high temperature

Perturbed angular correlation (PAC) spectroscopy of dilute zirconia alloys and YBa₂Cu₃0₇₋x, ceramic superconductors at elevated temperature have been measured using ¹¹¹Cd as the probe. The oxygen vacancy concentration in the zirconia samples was controlled by doping with yttrium or indium, which introduce vacancies, or with niobium, which removes vacancies. A well-defined distorted site was identified for ¹¹¹Cd in monoclinic pure zirconia above 700 °C; below 700 °C two additional sites appeared. Their populations are larger at lower temperatures, whereas the population of the other site becomes smaller. In the tetragonal pure, yttriumdoped, and indiumdoped zirconia a ¹¹¹Cd traps an oxygen vacancy, causing the PAC frequencies to decrease and the probe nuclei to relax. The association between the Cd and the oxygen vacancy is incomplete between 1000 and 1400°C. The trapping probability of the oxygen vacancies to the ¹¹¹Cd was deduced, and it is found to be a function of oxygen vacancy concentration and temperature. The association energy of the CdVo pair is 0.8(1) eV. When a vacancy is bound to a ¹¹¹Cd impurity, the vacancy hops among 8 nearest-neighboring anionic sites with an energy barrier of 0.8(1) eV. In 0.5 at.% Nbdoped tetragonal zirconia the relaxation of the ¹¹¹Cd probes was suppressed completely, and a small and near axially-symmetric electric field gradient (EFG) was measured. We interpret this as evidence that the lattice relaxes slightly around the ¹¹¹Cd probe to a more cubic-like configuration which accounts for the small EFG seen in this work. The microscopic structure of the YBa₂Cu₃0₇₋x depends on the detailed thermal history of the sample, and is far more complex than the xray or neutron diffraction have indicated. The samples processed in flowing air and cooled slowly after firing showed reproducible PAC spectra with a small, slightly nonaxially-symmetric EFG. These samples displayed standard orthorhombic YBa₂Cu307_x x-ray diffraction patterns at room temperature and have a very sharp Meissner flux exclusion transition at 92.7 K. The local structure of the slowly cooled YBa₂Cu₃0₇₋x was characterized between room temperature and 900°C. The orthorhombic PAC spectra were observed across the entire measured temperature range. We interpret this as evidence that the stable local structure of YBa₂Cu₃0₇₋x is orthorhombic. Between room temperature and 300°C the diffusive motion of oxygen causes detectable relaxation and the bulk activation energy is a few tenths of an eV