Microwave,ultraviolet, and soft X-Ray observations of hale region 16898     

Kiyoto Shibasaki  Franca Chiuderi-Drago  Mauro Melozzi  Cornelis Slottje  Ester Antonucci 《Solar physics》1983,89(2):307-321

Hale region 16898 was observed by the Westerbork Synthesis Radio Telescope at 6 cm and by the Ultraviolet Spectrometer and Polarimeter and the X-Ray Spectrometer on the Solar Maximum Mission satellite. Optical pictures of the same active region were taken at Sacramento Peak, Big Bear, and Meudon Observatories. The radio emission mechanisms are identified by comparing radio data with ultraviolet and soft X-ray data. The height of the radio sources and the magnetic field strength at that height are deduced. A radio source above a large sunspot shows a crescent shaped depression of circular polarization and a high brightness temperature. The emission mechanism is identified as gyroresonance at the second and the third harmonic layers and it is found that the second harmonic layer, where the magnetic field strength is 900 G, must be in the corona. An extended loop-like source connecting the leading and the following part of the active region as well as the sources associated with small spots are mainly due to thermal free-free emission by hot and dense plasma which is also observed in ultraviolet and soft X-ray radiation. The calculated radio brightness temperature, using the physical parameters deduced from the ultraviolet and soft X-ray line intensities, agrees with the observed brightness temperature. The height of the low brightness temperature sources above the small spots is 6000 ± 3000 km and that above the large spot is less than 3000 km: the source above the large spot does not show any shift relative to the sunspot due to the projection effect. Very strong radio emission was found which was associated with the merging of a group of small spots into the large sunspot. In the same day, warm ( 10⁶ K) and dense matter was present above the large spot. Evidence for nonthermal emission is presented.  相似文献   

Seasonal transition of hydrological processes in a slow‐moving landslide in a snowy region          下载免费PDF全文

Hikaru Osawa  Yuki Matsushi  Sumio Matsuura  Takashi Okamoto  Tatsuya Shibasaki  Hiroyuki Hirashima 《水文研究》2018,32(17):2695-2707

A comprehensive understanding of seasonal hydrological dynamics is required to describe the influence of pore‐water pressure on the stability of landslides in snowy regions. This study reports on the results of continuous meteorological and hydrological observations over 2 years on a landslide body comprising Neogene sedimentary rocks in northern Japan, where a thick (3–5 m) seasonal snowpack covers the land surface. Monitoring of the volumetric water content in shallow unsaturated zones (<0.8 m depth) and pore‐water pressure in saturated bedrock at depths of 2.0 and 5.2 m revealed clear seasonality in hydrological responses to rainfall and meltwater supply. During snow‐free periods, both the shallow soil moisture and deep pore‐water pressure responded rapidly to intense rainwater infiltration. In contrast, during snowmelt, the deep pore pressure fluctuated in accordance with the daily cycle of meltwater input, without notable changes in shallow moisture conditions. During occasional foehn events that cause intense snow melting in midwinter, meltwater flows preferentially through the layered snowpack, converging to produce a localized water supply at the ground surface. This episodically triggers a significant rise in pore‐water pressure. The seasonal differences in hydrological responses were characterized by a set of newly proposed indices for the magnitude and quickness of increases in the pressure head near the sliding surface. Under snow‐covered conditions, the magnitude of the pressure increase tends to be suppressed, probably owing to a reduction in infiltration caused by a seasonal decrease in the permeability of surface soils, and effective pore‐water drainage through the highly conductive colluvial layer. Deep groundwater flow within bedrock remained in a steady upwelling state, enhanced by increasing moisture in shallow soils under snow cover, reflecting the convergence of subsurface water from surrounding hillslopes.  相似文献   

基于空间模型的全球粮食安全评价   总被引：3，自引：1，他引：2  

吴文斌  唐华俊  杨鹏  游良志  周清波  陈仲新  柴崎亮介 《地理学报(英文版)》2011,21(1):3-17

This paper presents a scenario-based assessment of global future food security. To do that,the socio-economic and climate change scenarios were defined for the future and were linked to an integrated modeling framework. The crop yields simulated by the GIS-based Environmental Policy Integrated Climate (EPIC) model and crop areas simulated by the crop choice decision model were combined to calculate the total food production and per capita food availability,which was used to represent the status of food availability and stability. The per capita Gross Domestic Product (GDP) simulated by IFPSIM model was used to reflect the situation of food accessibility and affordability. Based on these two indicators,the future food security status was assessed at a global scale over a period of approximately 20 years,starting from the year 2000. The results show that certain regions such as South Asia and most African countries will likely remain hotspots of food insecurity in the future as both the per capita food availability and the capacity of being able to import food will decrease between 2000 and 2020. Low food production associated with poverty is the determining factor to starvation in these regions,and more efforts are needed to combat hunger in terms of future actions. Other regions such as China,most Eastern European countries and most South American countries where there is an increase in per capita food availability or an increase in the capacity to import food between 2000 and 2020 might be able to improve their food security situation.  相似文献   

Development of a GIS-based decision support system for assessing land use status     

Tan Guoxin  Ryosuke Shibasaki  Kanichiro Matsumura 《地球空间信息科学学报》2013,16(1):72-78

The objectives of this study are to assess land suitability and to predict the spatial and temporal changes in land use types (LUTs) by using GIS-based land use management decision support system. A GIS database with data on climate, topography, soil characteristic, irrigation condition, fertilizer application, and special socioeconomic activities has been developed and used for the evaluation of land productivity for different crops by integrating with a crop growth model—the erosion productivity impact calculator (EPIC). International food policy simulation model (IFPSIM) is also embedded into GIS for the predictions of how crop demands and crop market prices will change under alternative policy scenarios. An inference engine (IE) including land use choice model is developed to illustrate land use choice behavior based on logit models, which allows to analyze how diversified factors ranging from climate changes, crop price changes to land management changes can effect the distribution of agricultural land use. A test for integrated simulation is taken in each 0.1o by 0.1o grid cell to predict the change of agricultural land use types at global level. Global land use changes are simulated from 1992 to 2050.  相似文献   

Development of an automatic volcanic ash sampling apparatus for active volcanoes     

Taketo Shimano  Takeshi Nishimura  Nobuyuki Chiga  Yoshinobu Shibasaki  Masato Iguchi  Daisuke Miki  Akihiko Yokoo 《Bulletin of Volcanology》2013,75(12):1-7

We develop an automatic system for the sampling of ash fall particles, to be used for continuous monitoring of magma ascent and eruptive dynamics at active volcanoes. The system consists of a sampling apparatus and cameras to monitor surface phenomena during eruptions. The Sampling Apparatus for Time Series Unmanned Monitoring of Ash (SATSUMA-I and SATSUMA-II) is less than 10 kg in weight and works automatically for more than a month with a 10-kg lead battery to obtain a total of 30 to 36 samples in one cycle of operation. The time range covered in one cycle varies from less than an hour to several months, depending on the aims of observation, allowing researchers to target minute-scale fluctuations in a single eruptive event, as well as daily to weekly trends in persistent volcanic activity. The latest version, SATSUMA-II, also enables control of sampling parameters remotely by e-mail commands. Durability of the apparatus is high: our prototypes worked for several months, in rainy and typhoon seasons, at windy and humid locations, and under strong sunlight. We have been successful in collecting ash samples emitted from Showa crater almost everyday for more than 4 years (2008–2012) at Sakurajima volcano in southwest Japan.  相似文献   

Coronal Magnetography of Solar Active Region 8365 with the SSRT and NoRH Radio Heliographs     

B. I. Ryabov  V. P. Maksimov  S. V. Lesovoi  K. Shibasaki  A. Nindos  A. Pevtsov 《Solar physics》2005,226(2):223-237

Microwave maps of solar active region NOAA 8365 are used to derive the coronal magnetograms of this region. The technique is based on the fact that the circular polarization of a radio source is modified when microwaves pass through the coronal magnetic field transverse to the line of sight. The observations were taken with the Siberian Solar Radio Telescope (SSRT) on October 21 – 23 and with the Nobeyama Radio Heliograph (NoRH) on October 22 – 24, 1998. The known theory of wave mode coupling in quasi-transverse (QT) region is employed to evaluate the coronal magnetograms in the range of 10 – 30 G at the wavelength 5.2 cm and 50 – 110 G at 1.76 cm, taking the product of electron density and the scale of coronal field divergence to be constant of 10¹⁸ cm^–2. The height of the QT-region is estimated from the force-free field extrapolations as 6.2 × 10⁹ cm for the 20 G and 2.3 × 10⁹ cm for 85 G levels. We find that on large spatial scale, the coronal magnetograms derived from the radio observations show similarity with the magnetic fields extrapolated from the photosphere.  相似文献   

Energy transport and dynamics     

B. Schmieder  G. Peres  S. Enome  R. Falciani  P. Heinzel  J. C. Hénoux  J. Mariska  F. Reale  M. L. Rilee  B. Rompolt  K. Shibasaki  A. V. Stepanov  J. P. Wülser  D. Zarro  V. Zharkova 《Solar physics》1994,153(1-2):55-72

We report findings concerning energy transport and dynamics in flares during the impulsive and gradual phases based on new ground-based and space observations (notably fromYohkoh). A preheating sometimes occurs during the impulsive phase. Caxix line shifts are confirmed to be good tracers of bulk plasma motions, although strong blue shifts are not as frequent as previously claimed. They often appear correlated with hard X-rays but, forsome events, the concept that electron beams provide the whole energy input to the thermal component seems not to apply. Theory now yields: new diagnostics of low-energy proton and electron beams; accurate hydrodynamical modeling of pulse beam heating of the atmosphere; possible diagnostics of microflares (based on X-ray line ratio or on loop variability); and simulated images of chromospheric evaporation fronts. For the gradual phase, the continual reorganization of magnetic field lines over active regions determines where and when magnetic reconnection, the mechanism favoured for energy release, will occur. Spatial and temporal fragmentation of the energy release, observed at different wavelengths, is considered to be a factor as well in energy transport and plasma dynamics.Report of Team 4, Flares 22 Workshop, Ottawa, May 25–28, 1993.  相似文献   

Development of a GIS-based decision support system for assessing land use status   总被引：2，自引：0，他引：2  

Ryosuke Shibasaki  Kanichiro Matsumura 《地球空间信息科学学报》2004,7(1):72-78

IntroductionAgriculturallandusepatternsandtheirchangesaretightlyrelatedwithagriculturepolicyandfoodsecurityissuesundergrowingfooddemand,assess mentofglobalclimatechangeimpactsonagricul ture,environmentalissuesduetotheintensificationofagriculturallandusessuchaswaterpollution,soildegradation,andrecentlywaterscarcityissues.Soasustainableandholisticplanningandmanage mentoflandresourcesshouldcombineallthesere latedinformationwithefficienttoolsforassessmentandevaluationinordertopermitbroad ,interact…  相似文献   

On the spatial directivity of solar radio bursts     

I. E. Pogodin  A. G. Stupishin  K. Shibasaki 《Solar physics》1996,167(1-2):349-355

In this paper, a new method of estimating the spatial directivity (in the form of center-to-limb variation) of microwave burst emission is proposed and derived. Estimations of radioemission directivity values vs observation frequency are obtained. Results are compared to the radio source model using an inhomogeneous magnetic field, source size and particle density, and show a high degree of agreement. Values of model parameters from earlier estimations are confirmed.  相似文献   

Long-period pulsations of the thermal microwave emission of the solar flare of June 2, 2007 from data with high spatial resolution     

E. G. Kupriyanova  V. F. Melnikov  V. M. Puzynya  K. Shibasaki  H. S. Ji 《Astronomy Reports》2014,58(8):573-577

Data from the Nobeyama Radioheliograph at 17 GHz with high spatial and temporal resolution are used to detect quasi-periodic pulsations with periods from 55 to 250 s in the thermal component of the microwave emission of a solar flare loop observed on June 2, 2007. Observed pulsations with periods of about 110–120 s are co-phased along the entire loop axis. The observed periodicity is most likely due to modulation of the radio emission by slow magnetoacoustic waves trapped in the filamentary flare loop.  相似文献