bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tracking F-region plasma depletion bands using GPS-TEC, incoherent scatter radar, and all-sky imaging at Arecibo
Authors: Seker Ilgin , Livneh Dorey J. , Makela Jonathan J. , Mathews John D. 
Published: August 2014

Abstract
F-region plasma dynamics has been one of the main foci of the ionospheric research community for decades. The mid-latitude F-region has been considered to be relatively calm; however recent observations using highly sensitive CCD imaging systems and Global Positioning System (GPS) receivers have revealed that mid-latitude F-region mesoscale electrodynamics are more complex and this region is more active than usually assumed. Here we report combined incoherent scatter radar (ISR), imager, and GPS observations of F-region Medium-Scale Traveling Ionospheric Disturbance (MSTID) structures over the Arecibo Observatory in Puerto Rico. In particular, the plasma structures seen in the narrow-beam ISR cannot be understood fully without the all-sky images, which provide the context for the radar results—specifically, the spatial and temporal properties of the mesoscale structure. The GPS-derived total electron content (TEC) data provide additional information on the intensity of the MSTIDs. Here we present analysis of two specific plasma depletion events, which we prefer to call “MSTID bands”. Important results on the 3D geometry of these structures were found using a newly developed observation technique. For the first time, it is shown that the southern part of MSTID bands reaches higher altitudes than the northern part (vertically tilted by 12° towards magnetic south). These results give a much broader perspective on nighttime, mid-latitude F-region structure and point to new ways of interpreting these structures and how they appear in ISR results.
Time-evolution of bubble formation in a viscous liquid
Authors: Yamada Kou , Emori Hiroyuki , Nakazawa Kiyoshi 
Published: August 2014

Abstract
Time-evolutions of bubble vesiculation in viscous liquid are characterized by two stages, i.e., the bubble formation stage and the bubble coalescence stage. We have focused on the former stage of bubble vesiculation and investigated numerically bubble formation in decompressed viscous liquid. Bubble formation consists of nucleation and growth of bubbles due to the exsolution of volatile elements from liquid. In order to describe the bubble formation processes, we have developed a theoretical model, taking into account the bubble size distribution and the viscosity of liquid, on the base of the model proposed by Toramaru (J. Geophys. Res., 100, 1913–1931, 1995). Numerical solutions show that the feature of bubble nucleation is significantly varied according to the magnitude of the liquid viscosity. In low viscosity cases, the growth of bubbles is mainly controlled by the diffusive flux of volatile molecules to bubbles. The number density of bubbles is sensitive to the diffusivity of volatile element in liquid. On the other hand, bubbles hardly grow in the case of the extremely high viscosity. Therefore, bubbles continue to be formed in order to reduce the volatile oversaturation of liquid. In the case of the intermediate viscosity, bubbles grow to the large size slowly by the viscous resistance. After the nucleation of bubbles ceases, the Ostwald ripening occurs and leads to the dissolution of small bubbles. The number density of bubbles varies greatly with time. The time-evolutions of the bubble size distribution have been also caluclated. In the case of the low and extreme high viscosity, the bubble size distribution evolves as an unimodal size distribution. In the case of the moderate viscosity, the size distribution of bubbles shows the distribution with a wider dispersion. These characteristic time-evolutions of the number density and size distribution of bubbles would be useful in evaluating material quantities such as the diffusivity, the viscosity, and the surface tension of liquid from experimental results. Furthermore our results provide the number density and size distribution of bubbles just before bubble coalescence occurs.
Probability distribution of orbital crossing times in a protoplanetary system
Authors: Emori Hiroyuki , Nakazawa Kiyoshi , Iwasaki Kazunori 
Published: August 2014

Abstract
Long term behavior of five protoplanets was studied under the same conditions as those used in Chambers et al. (1996). One major difference was the number of calculations carried out for one parameter set of initial orbital distance. We reconfirmed their result for the orbital crossing times among five protoplanets starting from circular and co-planar orbits with an equal distance of their semi major axes. For each distance, the distribution of orbital crossing times was calculated from 500 sets of azimuthal positions of protoplanets randomly chosen. The distribution of the times around the average value resembles each other for almost all orbital distance cases. Based on a statistical certification we conclude that the fluctuations in orbital crossing times take “the log normal function”. The dispersion of the log normal distribution function is equal to 0.2. This means that 70% of the events of orbital crossing occurs in the range between 10−0.2 times earlier and 100.2 times later than the average orbital crossing time.
Efficient GPS receiver DCB estimation for ionosphere modeling using satellite-receiver geometry changes
Authors: Hong Chang-Ki , Grejner-Brzezinska Dorota A. , Kwon Jay Hyoun 
Published: August 2014

Abstract
A new and efficient algorithm using the geometry conditions between satellite and tracking receivers is proposed to determine the receiver differential code bias (DCB) using permanent reference stations. This method does not require a traditional single-layer ionosphere model and can be used for estimating DCBs of receivers in a regional network as long as one of the receiver DCBs is already known. The main underlying rationale for this algorithm is that the magnitude of the signal delay caused by the ionosphere is, under normal conditions, highly dependent on the geometric range between the satellite and the receiver. The proposed algorithm was tested with the Ohio Continuously Operating Reference Stations (CORS) sub-network data. The results show that quality comparable to the traditional DCB estimation method is obtainable by implementing this simple algorithm.
Well-resolved hypocenter distribution using the double-difference relocation method in the region of the 2007 Chuetsu-oki Earthquake
Authors: Yukutake Yohei , Takeda Tetsuya , Obara Kazushige 
Published: August 2014

AbstractThe 2007 Chuetsu-oki Earthquake (Mj= 6.8) occurred in the eastern margin of the Japan Sea where high strain rates have been observed and many large earthquakes have occurred. The main shock was located near the Western Nagaoka Basin active fault system dipping in the westward direction. We estimated the well-resolved hypocenter location around the main shock rupture zone from the differential arrival times obtained by both manual picking and waveform cross-correlation analysis. From the relocated aftershock distributions, we successfully resolved the detailed fault structures activated by the main shock. The estimated fault model resolves four individual fault segments. The fault model suggests that the main shock predominantly ruptured the southeastward dipping fault planes. On the other hand, the aftershocks around the hypocenter of the main shock occurred on both the northwestward and southeastward dipping fault planes. Both fault planes around the hypocenter of the main shock may have been nearly coincidentally ruptured during the main shock.
Precise aftershock distribution of the 2007 Chuetsu-oki Earthquake obtained by using an ocean bottom seismometer network
Authors: Shinohara Masanao , Kanazawa Toshihiko , Yamada Tomoaki , Nakahigashi Kazuo , Sakai Shin’ichi , Hino Ryota , Murai Yoshio , Yamazaki Akira , Obana Koichiro , Ito Yoshihiro , Iwakiri Kazuhiro , Miura Ryo , Machida Yuya , Mochizuki Kimihiro , Uehira Kenji , Tahara Michitaka , Kuwano Asako , Amamiya Shin’ichiro , Kodaira Shuichi , Takanami Tetsuo , Kaneda Yoshiyuki , Iwasaki Takaya 
Published: August 2014

Abstract
The Chuetsu-Oki Earthquake occurred on July 16, 2007. To understand the mechanism of earthquake generation, it is important to obtain a detailed seismic activity. Since the source region of the 2007 Chuetsu-oki Earthquake lies mainly offshore of Chuetsu region, a central part of Niigata Prefecture, it is difficult to estimate the geometry of faults using only the land seismic network data. A precise aftershock distribution is essential to determine the fault geometry of the mainshock. To obtain the detailed aftershock distribution of the 2007 Chuetsu-oki Earthquake, 32 Ocean Bottom Seismometers (OBSs) were deployed from July 25 to August 28 in and around the source region of the mainshock. In addition, a seismic survey using airguns and OBSs was carried out during the observation to obtain a seismic velocity structure below the observation area for precise hypocenter determination. Seven hundred and four aftershocks were recorded with high spatial resolution during the observation period using OBSs, temporally installed land seismic stations, and telemetered seismic land stations and were located using the double-difference method. Most of the aftershocks occurred in a depth range of 6–15 km, which corresponds to the 6-km/s layer. From the depth distribution of the hypocenters, the aftershocks occurred along a plane dipping to the southeast in the whole aftershock region. The dip angle of this plane is approximately 40°. This single plane with a dip to the southeast is considered to represent the fault plane of the mainshock. The regions where few aftershocks occurred are related to the asperities where large slip is estimated from the data of the mainshock. The OBS observation is indispensable to determine the precise depths of events which occur in offshore regions even close to a coast.
Global distribution of the thermospheric disturbances produced by effects from the upper and lower regions: simulations by a whole atmosphere GCM
Authors: Fujiwara Hitoshi , Miyoshi Yasunobu 
Published: August 2014

Abstract
It is well-known that low-latitude ionospheric/thermospheric disturbances are sometimes generated in association with the passage of traveling ionospheric/atmospheric disturbances (TIDs/TADs) produced in the high-latitude region and that the low-latitude ionosphere/thermosphere should be strongly coupled with the lower atmosphere. These facts suggest that the appearance of thermospheric disturbances with complex structures in the low-latitude region are the result of a superposition of disturbances which have different origins. We have investigated the lower atmospheric effects on the morphology of the thermospheric disturbances in response to changes in the geomagnetic activity by using a whole atmosphere general circulation model (GCM). In order to suppress the lower atmospheric effects, we set the global mean temperature and zero-wind below about 80-km altitude in the GCM. The simulation results show that the lower atmospheric effects can produce latitudinal and longitudinal structures in the low-latitude thermosphere. These lower atmospheric effects also modulate the amplitudes and structures of TADs propagating from the high- to low-latitude regions. Our results suggest that the lower atmospheric effects can produce variability in the TIDs/TADs, which in turn would create conditions conducive to plasma instabilities in the low-latitude ionosphere.
Upward propagating tidal effects across the E- and F-regions of the ionosphere
Authors: Immel Thomas J. , England Scott L. , Zhang Xiaoli , Forbes Jeffrey M. , DeMajistre Robert 
Published: August 2014

Abstract
Recent far-ultraviolet (FUV) observations of Earth have shown the remarkable spatial correspondence between the amplitude of non-migrating atmospheric tides originating in the troposphere and the density and morphology of the nighttime equatorial ionospheric anomaly (EIA). This is likely a result of the modulation of the E-region dynamo electric field in daytime by the tidal winds. FUV observations around the time of the vernal equinox of 2002 show that the signature of tidal influence, the wave-4 periodicity in the separation and density of the two EIA bands, itself exhibits significant temporal variability. Here, we seek to understand this variability, and whether (or not) it is linked to variations in the strength of the upward-propagating tides. This study relies on tidal measurements provided by the global observations from the TIMED-SABER instrument that measures the temperature variations in the MLT associated with the upward-propagating tides. TIMED-GUVI provides F-region density measurements concurrent to the MLT temperature retrievals. It is found that the atmospheric and ionospheric zonal wave-4 signatures very nearly covary over a 30-day period, strongly supporting the theory that the influence of the the diurnal eastward 3 (DE3) tide originating in the troposphere extends to the F-layer of the ionosphere. Additionally, a 6-day periodicity in the power of the ionospheric wave-4 signature is found that may originate with the tide’s interaction with longer period planetary waves.
Temporal and spatial distributions of atmospheric wave energy in the equatorial stratosphere revealed by GPS radio occultation temperature data obtained with the CHAMP satellite during 2001–2006
Authors: Tsuda Toshitaka , Venkat Ratnam M. , Alexander Simon P. , Kozu Toshiaki , Takayabu Yukari 
Published: August 2014

Abstract
Using stratospheric temperature profiles derived from GPS radio occultation (RO) measurements made by the German CHAMP satellite from June 2001 to May 2006, we studied the climatological behavior of atmospheric wave activity in the tropics. The wave potential energy, E
p, is calculated from temperature fluctuations with vertical scales shorter than 7 km in a longitude and latitude cell of 20° × 10° at 19–26 km. E
p is then averaged every 3 months (June–July–August (JJA), September–October–November (SON), December–January–February (DJF), March–April–May (MAM)), and the averages are compared with the cloud top temperature from outgoing long-wave radiation (OLR) and the convective rain rate from the TRMM precipitation radar (PR). E
p at 19–26 km in the western Pacific to Indian Ocean is found to show a clear seasonal variation, with a large E
p during DJF and MAM and a considerably enhanced E
p in SON; it becomes minimum during JJA near the equator, when the center of the enhanced E
p region appears over north India and the Indochina peninsula. Localized enhancement of E
p seems to be mainly due to atmospheric gravity waves. In addition, the longitudinally elongated portion of E
p is partially affected by Kelvin wave-like disturbances with short horizontal scales. In DJF and MAM, the convective clouds are located over the western Pacific and around Indonesia, at which time the Kelvin wavelike disturbances are effectively generated. The spatial and seasonal variations of E
p are closely related to the distribution of clouds, implying that convective wave generation is very important in the tropics. However, wave-mean flow interactions due to the wind shear of the QBO become important in the lower stratosphere, which considerably modifies our analysis of the E
p distribution at 19–26 km. Therefore, both wave generation and propagation characteristics must be taken into account in describing the climatological behavior of atmospheric wave activity in the equatorial stratosphere.
Changes to magnetic minerals caused by frictional heating during the 1999 Taiwan Chi-Chi earthquake
Authors: Mishima Toshiaki , Hirono Tetsuro , Nakamura Norihiro , Tanikawa Wataru , Soh Wonn , Song Sheng-Rong 
Published: August 2014

Abstract
We carried out magnetic mineral analyses of samples from the shallowest major fault zone within the Chelungpu fault system, which is the zone that previous researchers believe slipped during the 1999 Taiwan Chi-Chi earthquake. Our aim was to gain an understanding of the changes to magnetic minerals during the earthquake. Magnetic hysteresis and low-temperature thermal demagnetization measurements showed that high magnetic susceptibilities in the black gouge zone within the major fault zone could be attributed not to fining of ferrimagnetic minerals but, rather, to their abundance. Thermomagnetic analyses indicated that the strata in and around the fault zone originally contained thermally unstable iron-bearing paramagnetic minerals, such as pyrite, siderite, and chlorite. We therefore concluded that frictional heating (>400°C) occurred in the black gouge zone in the major fault zone during the slip of the Chi-Chi earthquake and that the resultant high temperature induced thermal decomposition of paramagnetic minerals to form magnetite, resulting in the observed high magnetic susceptibilities.
Earthquake fault of the 26 May 2006 Yogyakarta earthquake observed by SAR interferometry
Authors: Tsuji Takeshi , Yamamoto Katsuya , Matsuoka Toshifumi , Yamada Yasuhiro , Onishi Kyosuke , Bahar Alfian , Meilano Irwan , Abidin Hasanuddin Z. 
Published: August 2014

Abstract
We analyzed synthetic aperture radar interferometry (InSAR) to reveal surface deformation associated with the 26 May 2006 Yogyakarta earthquake, for which the fault location and geometry have not been clearly determined. Our results demonstrate that surface deformation occurred ∼10 km east of the Opak River fault thought to be the source of the May 2006 event and that the probable causative fault delineated in this study is consistent with aftershock epicenters determined by a temporary seismic network. The trace of the causative fault bends at its southern termination toward the Opak River fault as if it were a splay. Our data demonstrate that another probable slip plane extends across Yogyakarta and that the heavily damaged areas covered by young volcanic deposits may have undergone subsidence during the earthquake.
What ancient scalar satellite data can tell us about the 1969 geomagnetic jerk?
Authors: Yahiat Y. , Hamoudi M. , Mandea M. 
Published: August 2014

Abstract
The linearity of the secular variation of the Earth’s magnetic field is irregularly broken by sudden changes in its trend, known as geomagnetic jerks. Detecting these events in the temporal variations of the magnetic field components continues to be an exciting topic, mainly recently when their investigation rely not more only on observatory data, but as well as on measurements provided by satellites. We have also been interested by these magnetic events, and one of the central aims of our work has been to determine whether the satellite scalar data, obtained in the sixties and early seventies are able to reveal the existence of such a geomagnetic jerk, previously detected around 1969, in observatory annual or monthly means. For this purpose, we have used available OGO2, OGO4 and OGO6 satellite intensity data covering the period 1965–1971. Another motivation of re-processing and analyzing these old satellite datasets has been to better estimate their role in the global core field modeling, especially in describing the secular variation. Our results indicate that these ancient magnetic satellite datasets contain valuable information to characterize the secular variation over the time-span they are available, and allow to detect the geomagnetic jerk around 1969.
Nighttime D-region equivalent electron density determined from tweek sferics observed in the South Pacific Region
Authors: Kumar Sushil , Deo Anil , Ramachandran V. 
Published: August 2014

Abstract
Atmospherics or sferics that originate from lightning discharges on propagating large distances in the Earthionosphere waveguide, particularly at the night, form dispersed sferics called tweeks. Tweeks are novel diagnostic tool to monitor the nighttime D-region ionosphere. Mean equivalent electron density n
em at mean tweek reflection heights h
m and electron density profile have been estimated using the higher harmonic tweeks recorded in the time between 21–03 hrs LT at Suva (18.2°S, 178.3°E), Fiji, during a period March–December 2006. The values of nem vary from 29–170 cm−3 in the altitude range of about 3.5 km at h
m of about 83 km. In terms of usually used exponential electron density profile, the ionospheric reference height and the exponential sharpness factor are calculated to be 83.1 km and 0.64 km−1, respectively. The scale height is calculated to be 1.9 km. Equivalent electron density profile of the nighttime lower ionosphere, using tweek method, shows lower values of electron density by about 20–45% than those obtained from the IRI-2001 model.
Differences in tsunami generation between the December 26, 2004 and March 28, 2005 Sumatra earthquakes
Authors: Geist Eric L. , Bilek Susan L. , Arcas Diego , Titov Vasily V. 
Published: August 2014

AbstractSource parameters affecting tsunami generation and propagation for theMw> 9.0 December 26, 2004 and theMw= 8.6 March 28, 2005 earthquakes are examined to explain the dramatic difference in tsunami observations. We evaluate both scalar measures (seismic moment, maximum slip, potential energy) and finite-source representations (distributed slip and far-field beaming from finite source dimensions) of tsunami generation potential. There exists significant variability in local tsunami runup with respect to the most readily available measure, seismic moment. The local tsunami intensity for the December 2004 earthquake is similar to other tsunamigenic earthquakes of comparable magnitude. In contrast, the March 2005 local tsunami was deficient relative to its earthquake magnitude. Tsunami potential energy calculations more accurately reflect the difference in tsunami severity, although these calculations are dependent on knowledge of the slip distribution and therefore difficult to implement in a real-time system. A significant factor affecting tsunami generation unaccounted for in these scalar measures is the location of regions of seafloor displacement relative to the overlying water depth. The deficiency of the March 2005 tsunami seems to be related to concentration of slip in the down-dip part of the rupture zone and the fact that a substantial portion of the vertical displacement field occurred in shallow water or on land. The comparison of the December 2004 and March 2005 Sumatra earthquakes presented in this study is analogous to previous studies comparing the 1952 and 2003 Tokachi-Oki earthquakes and tsunamis, in terms of the effect slip distribution has on local tsunamis. Results from these studies indicate the difficulty in rapidly assessing local tsunami runup from magnitude and epicentral location information alone.
Block copolymers comprising a polytetrahydrofuran block and one or two [5]-polyurethane block(s): synthesis and characterization
Authors: Kušan Jacqueline , Keul Helmut , Höcker Hartwig 
Published: August 2014

AbstractA-B Di- and B-A-B triblock copolymers with poly(tetramethyleneoxy) (poly(THF)) and poly(tetramethyleneoxycarbonylimino) (poly(TeU)) blocks were prepared by sequential polymerization of tetrahydrofuran (THF) and tetramethyleneurethane (TeU) with the monofunctional initiator methyl trifluormethylsulfonate and the bifunctional initiator trifluoromethanesulfonic acid anhydride, respectively. The block copolymers obtained after purification exhibit a monomodal narrow molecular weight distribution and a uniform microstructure of the two blocks as was deduced from gel permeation chromatography and NMR analysis. The block copolymers are semicrystalline materials with distinct melting points of the poly(THF) and the poly(TeU) domains.