Solar flares observed in microwaves: Recent results from solar radio groups in Japan     

Kosugi  Takeo 《Solar physics》1982,113(1-2):327-332

Recent observational studies on solar flares made by solar radio groups in Japan during the period around the maximum of Cycle 21 are briefly reviewed. Much attention is paid especially to comparison studies of microwave observations with hard X-ray and -ray observations.  相似文献   

Radio and X-ray observations of a multiple impulsive solar burst with high time resolution     

Takeo Kosugi 《Solar physics》1981,71(1):91-105

A well-developed multiple impulsive microwave burst occurred on February 17, 1979 simultaneously with a hard X-ray burst and a large group of type III bursts at metric wavelengths. The whole event is composed of several subgroups of elementary spike bursts. Detailed comparisons between these three classes of emissions with high time resolution of 0.5 s reveal that individual type III bursts coincide in time with corresponding elementary X-ray and microwave spike bursts. It suggests that a non-thermal electron pulse generating a type III spike burst is produced simultaneously with those responsible for the corresponding hard X-ray and microwave spike bursts. The rise and decay characteristic time scales of the elementary spike burst are 1 s, 1 s and 3 s for type III, hard X-ray and microwave emissions respectively. Radio interferometric observations made at 17 GHz reveal that the spatial structure varies from one subgroup to others while it remains unchanged in a subgroup. Spectral evolution of the microwave burst seems to be closely related to the spatial evolution. The spatial evolution together with the spectral evolution suggests that the electron-accelerating region shifts to a different location after it stays at one location for several tens of seconds, duration of a subgroup of elementary spike bursts. We discuss several requirements for a model of the impulsive burst which come out from these observational results, and propose a migrating double-source model.  相似文献   

Urban change detection related to earthquakes using an adaptive nonlinear mapping of high-resolution images   总被引：1，自引：0，他引：1  

Kosugi  Y. Sakamoto  M. Fukunishi  M. Wei Lu Doihara  T. Kakumoto  S. 《Geoscience and Remote Sensing Letters, IEEE》2004,1(3):152-156

We propose a nonlinear mapping method for detecting geographical changes. In our system, two images photographed at different points of time are checked based on an iterative nonlinear mapping. The system automatically extracts feature changes of aerial imageries by computing distribution of the image matching score. We evaluate the change detection ability by using the receiver operating characteristic under misregistration cases, including rotational misalignments.  相似文献   

Identification of tsunami deposits considering the tsunami waveform: An example of subaqueous tsunami deposits in Holocene shallow bay on southern Boso Peninsula, Central Japan     

Osamu Fujiwara  Takanobu Kamataki   《Sedimentary Geology》2007,200(3-4):295-313

This study proposes a tsunami depositional model based on observations of emerged Holocene tsunami deposits in outcrops located in eastern Japan. The model is also applicable to the identification of other deposits, such as those laid down by storms. The tsunami deposits described were formed in a small bay of 10–20-m water depth, and are mainly composed of sand and gravel. They show various sedimentary structures, including hummocky cross-stratification (HCS) and inverse and normal grading. Although, individually, the sedimentary structures are similar to those commonly found in storm deposits, the combination of vertical stacking in the tsunami deposits makes a unique pattern. This vertical stacking of internal structures is due to the waveform of the source tsunamis, reflecting: 1) extremely long wavelengths and wave period, and 2) temporal changes of wave sizes from the beginning to end of the tsunamis.

The tsunami deposits display many sub-layers with scoured and graded structures. Each sub-layer, especially in sandy facies, is characterized by HCS and inverse and normal grading that are the result of deposition from prolonged high-energy sediment flows. The vertical stack of sub-layers shows incremental deposition from the repeated sediment flows. Mud drapes cover the sub-layers and indicate the existence of flow-velocity stagnant stages between each sediment flow. Current reversals within the sub-layers indicate the repeated occurrence of the up- and return-flows.

The tsunami deposits are vertically divided into four depositional units, Tna to Tnd in ascending order, reflecting the temporal change of wave sizes in the tsunami wave trains. Unit Tna is relatively fine-grained and indicative of small tsunami waves during the early stage of the tsunami. Unit Tnb is a protruding coarse-grained and thickest-stratified division and is the result of a relatively large wave group during the middle stage of the tsunami. Unit Tnc is a fine alternation of thin sand sheets and mud drapes, deposited from waning waves during the later stage of the tsunami. Unit Tnd is deposited during the final stage of the tsunami and is composed mainly of suspension fallout. Cyclic build up of these sub-layers and depositional units cannot be explained by storm waves with short wave periods of several to ten seconds common in small bays.  相似文献   

Phase relations in the tremolite-pargasite join     

Takanobu Oba 《Contributions to Mineralogy and Petrology》1980,71(3):247-256

The join tremolite (Tr)-pargasite (Pa) has been studied in the temperature range 750 °–1,150 ° C under a water vapor pressure of 1 and 5 kbar. There is a continuous solid solution series between the compositions Tr₈₅Pa₁₅ and Tr_oPa₁₀₀ at 850 ° C and 5 kbar. Tremolite and pargasite are separated by a solvus at 1 kbar and the field of tremolitic amphibole +pargasitic amphibole+vapor is present in the region between Tr₉₀Pa₁₀ and Tr₁₀Pa₉₀ at 800 ° C. The phase assemblages at 850 ° C and 1 kbar change as follows with increasing pargasite component; clinopyroxene +orthopyroxene+quartz+vapor, tremolitic amphibole+vapor, tremolitic amphibole+clinopyroxene +forsterite+plagioclase+vapor, tremolitic amphibole+pargasitic amphibole+vapor, and pargasitic amphibole+vapor. The petrological significance of amphibole pairs in metamorphic rocks is discussed on the basis of the experimental results.  相似文献   

The effects of rock fragments on hydrologic and hydraulic responses along a slope     

Kou‐Chan Hung  Ken'ichirou Kosugi  Tim Hau Lee  Takahisa Misuyama 《水文研究》2007,21(10):1354-1362

A model describing the three‐dimensional matrix flow along a slope with rock fragments or impermeable blocks was developed. The model was combined with modified Picard's iteration to ensure mass conservation in the unsaturated flow. We found that rock fragments obstruct water flow along the slope. The groundwater table must be raised to provide a sufficient pore water pressure gradient to facilitate water flow, but higher pore water pressure may induce slope failure. We also conducted a bench‐scale laboratory flume experiment to examine the effects of impermeable blocks on downstream seepage flow. In addition, a numerical experiment was conducted to examine how different arrangements of impermeable blocks affect downstream seepage flow and pore water pressure. This research demonstrated that the hydraulic phenomena were affected when impermeable blocks were present, and pore water pressure increased as the position of impermeable blocks was lowered. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

A pair of behind-the-limb solar flares of 1984 May 21     

Kosugi  Takeo 《Solar physics》1987,113(1-2):295-298

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Time variations of hard X-ray bursts observed with the Solar X-ray Telescope aboard Hinotori (with a movie)     

Takeo Kosugi  Saku Tsuneta 《Solar physics》1983,86(1-2):333-338

We have developed a new method for synthesizing hard X-ray maps from the raw data of the Solar X-ray Telescope (SXT) aboard Hinotori. Using this method we analyzed five typical SXT events and summarized their images in a movie with a time resolution of about 8 s (half spin period of the satellite). The movie clearly shows that (1) three different classes of bursts, i.e., the gradual thermal burst, the multiple impulsive burst, and the extended outburst, have different structures and show quite different variations from each other, and that (2) the source of the extended outburst is located in the corona above 10⁴ km and its shape appears to be a large loop.  相似文献   

Measurement of methane flux over an evergreen coniferous forest canopy using a relaxed eddy accumulation system with tuneable diode laser spectroscopy detection     

Ayaka Sakabe  Ken Hamotani  Yoshiko Kosugi  Masahito Ueyama  Kenshi Takahashi  Akito Kanazawa  Masayuki Itoh 《Theoretical and Applied Climatology》2012,109(1-2):39-49

Very few studies have conducted long-term observations of methane (CH₄) flux over forest canopies. In this study, we continuously measured CH₄ fluxes over an evergreen coniferous (Japanese cypress) forest canopy throughout 1?year, using a micrometeorological relaxed eddy accumulation (REA) system with tuneable diode laser spectroscopy (TDLS) detection. The Japanese cypress forest, which is a common forest type in warm-temperate Asian monsoon regions with a wet summer, switched seasonally between a sink and source of CH₄ probably because of competition by methanogens and methanotrophs, which are both influenced by soil conditions (e.g., soil temperature and soil moisture). At hourly to daily timescales, the CH₄ fluxes were sensitive to rainfall, probably because CH₄ emission increased and/or absorption decreased during and after rainfall. The observed canopy-scale fluxes showed complex behaviours beyond those expected from previous plot-scale measurements and the CH₄ fluxes changed from sink to source and vice versa.  相似文献   

Discovery of an ice cave in the Yatude Valley, Langhovde, Dronning Maud Land, East Antarctica   总被引：1，自引：0，他引：1  

Takanobu Sawagaki  Hideki Miura  Shogo Iwasaki 《Polar Science》2008,2(4):287-294

A circular hole was discovered on the downstream side of a glacier dam in the Yatude Valley, Langhovde, East Antarctica, during the 2005–2006 austral summer. The opening of this hole is the first opportunity enabling us to observe the interior of the dam. The opening led to a large cave in the dam, raising the possibility of meltwater drainage through the dam. The Yatude Valley is an approximately U-shaped fluvial valley. The valley floor has been incised to form a box-shaped inner valley that contains fluvial terraces and large boulders upon the valley floor. The origin of these features can be explained by a large amount of running water; however, we consider it unlikely that a regular current has flowed through this site for a long period. Instead, it is more likely that large quantities of lake water have been periodically discharged due to collapse of the glacier dam or spilling out through a tunnel channel within the cave. The discovered hole and the ice cave are key features in understanding the historical development of the Yatude Valley in relation to the melting history of the Antarctic ice sheet.  相似文献