A5061822821- Geomagnetism and Paleomagnetism Studies
- Geological and Geochemical Analysis
- Geology and Paleoclimatology Research
- Geological and Geophysical Studies
- Geophysical and Geoelectrical Methods
- Astro and Planetary Science
- earthquake and tectonic studies
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Planetary Science and Exploration
- Radio Astronomy Observations and Technology
- Methane Hydrates and Related Phenomena
- Earthquake Detection and Analysis
- Geochemistry and Geologic Mapping
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- GNSS positioning and interference
- Astronomical Observations and Instrumentation
- Geological Studies and Exploration
- Magnetic and Electromagnetic Effects
- Stellar, planetary, and galactic studies
- Advanced Wireless Communication Techniques
- Geophysical Methods and Applications
- Hydrocarbon exploration and reservoir analysis
- Seismic Waves and Analysis
Kumamoto University
2015-2024
Graduate School USA
2016
Japan Aerospace Exploration Agency
2007-2012
Institute of Space and Astronautical Science
2005-2012
National Institute of Advanced Industrial Science and Technology
2007-2009
Tokyo Institute of Technology
2004-2007
NTT (Japan)
1999-2005
Earth’s last magnetic field reversal was complex, with excursions at 795 and 784 ka before a final polarity flip 773 ka.
[1] We have conducted a paleointensity study of the Matuyama-Brunhes (M-B) polarity transition recorded in 34 successive lava flows Punaruu Valley on Tahiti. A reversed is obtained from lower part record, major directional changes are derived middle and normal upper record. These paleomagnetic directions five 40Ar/39Ar ages yielding weighted mean 771 ± 8 (1σ) ka indicate that 30 geomagnetic field across M-B transition. The 215 specimens 32 were subjected to double-heating technique Shaw...
We performed astrometric observations with the VLBA of WB89-437, an H2O maser source in Outer spiral arm Galaxy. measure annual parallax 0.167 +/- 0.006 mas, corresponding to a heliocentric distance 6.0 0.2 kpc or Galactocentric 13.4 kpc. This value for is considerably smaller than kinematic 8.6 confirms presence faint toward l = 135 degrees. also measured full space motion object and find large peculiar ~20 km/s Galactic center. explains error estimate. that WB89-437 has same rotation speed...
Abstract This paper reports the first in situ magnetic hysteresis measurements of pseudo‐single‐domain (PSD) magnetite under high pressure up to 1 GPa. The stoichiometric PSD samples hydrostatic were carried out using a piston‐cylinder high‐pressure cell, and dependence parameters was calculated from curves. It found that coercivity ( B c ) increases with increasing as quadratic function GPa by ∼90%, which is different dependences multidomain single‐domain magnetites. Coercivity remanence...
The electron density distribution in the vicinity of lunar surface was explored with radio occultation technique using a subsatellite on SELENE mission. Although measurements suffer from contamination by terrestrial ionosphere and interplanetary plasma, an analysis more than 300 provides adequate statistics reveals general trend. result suggests that dense covering whole sunlit side, as suggested Soviet Luna 19 22 missions, does not exist. However, weak signatures enhancement densities order...
K-Ar age determinations were made on two monogenetic volcanoes in the Auckland volcanic field, New Zealand, which have recorded geomagnetic excursions. For Wiri volcano with north-down intermediate paleomagnetic direction, five samples gave a weighted mean of 27 ± 5 (1σ) ka. Hampton Park west-up three 55 Since these ages are distinguished at 2σ level, it is inferred that least excursions can be recognized Auckland. The barely from established range Laschamp excursion (39–45 ka) level....
Abstract High‐resolution vector magnetic measurements were performed on five hydrothermal vent fields of the back‐arc spreading region southern Mariana Trough using Shinkai 6500 , a deep‐sea manned submersible. A new 3‐D forward scheme was applied that exploits surrounding bathymetry and varying altitudes submersible to estimate absolute crustal magnetization. The results revealed magnetic‐anomaly‐derived magnetizations show reasonable correlation with natural remanent rock samples collected...
Abstract We have carried out paleomagnetic analyses of tephras from the Taupō eruption, one most violent eruptions on Earth in past 5000 years. Pyroclastic deposits were collected with 7 cm 3 cubes pushed into each unit eruption sequence, consisting airfall units and overlying ignimbrite. Where possible, we targeted fine-ash layers matrix, as lapilli sized material can significantly affect quality analysis. The samples oriented using a collection device specially designed to maximize...
Abstract Three different excursional paleomagnetic directions were reported from eight volcanoes of the Auckland volcanic field in New Zealand: north-down (ND) obtained five volcanoes, west-up (WU) two and south-up (SU) one volcano. K-Ar ages have been for these volcanoes: 27±5 (1σ) ka Wiri volcano ND group 55±5 Hampton Park WU group. In present study, we carried out further age determinations on three other reliable them: 30±5 Puketutu 50±6 McLennan Hills SU The agrees well with that Wiri,...
During the SELENE (Kaguya) mission dual‐spacecraft radio occultation technique was used to investigate electron population in vicinity of lunar surface. One pair coherent S‐band signals from one spacecraft probe possible density enhancement near Moon, and another signal other measured solar wind terrestrial ionosphere plasma fluctuations, which also exist measurement by former pair. The results suggest that any stable with densities comparable ones observed Soviet Luna 19 22 missions does...
Abstract We investigated temporal changes in the rock-magnetic properties of volcanic ash ejected from Aso Nakadake volcano during a sequence eruptions 2019 to 2020. For 39 samples, magnetic hysteresis parameters, including saturation magnetization ( M s ), remanent rs coercivity B c and remanence cr were obtained. Curie temperature T ) samples was also estimated using thermomagnetic analyses. Titanium-rich -poor titanomagnetites dominant minerals ash, which titanium-rich phase dominant....
Lavas erupted at the Society hotspot during Matuyama‐Brunhes (M‐B) polarity reversal record transitional field behavior containing two tight paleodirectional groups that when averaged are antipodal 95% confidence level, and thus correlate to clustered virtual geomagnetic poles (VGPs). The occurrence of these observations––data obtained from published records M‐B transition distinct sections a succession flows on Tahiti––is associated with time strength axial dipole was significantly reduced....
Abstract Long‐distance lateral magma transport within the crust has been inferred for various magmatic systems including oceanic island volcanoes, mid‐oceanic ridges, and large igneous provinces. However, studying physical chemical properties of active fissure is difficult. Hence, this study investigates movement away from Mull volcano in North Atlantic Igneous Province, where erosion exposed its upper crustal dike networks. Magmatic lineations dikes indicate that flow suite changed near...
In this paper, we propose a new signal-repetition-based frequency and timing synchronization technique for burst OFDM modem in the severe fading environments typical of broadband wireless communication systems. The repeated signals are added at beginning radio packets agility. proposed employs weighting function correlation calculation based on identical signal repetition approach. computer simulation results show that significantly improves carrier offset estimation detection performance...
This paper proposes a transmission diversity (TD) technique combined with orthogonal frequency division multiplex (OFDM) modulation to enhance packet-error-rate (PER) performance in microcell broadband wireless communication systems. The proposed TD selects the antenna anticipated better-channel conditions subchannel-by-subchannel manner at access point (AP) based on quality-measurement results of signals sent by mobile terminal (MT). In subsequent timing from AP MT, each station transmits...