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11.
A number of statistical methods are typically used to effectively predict potential landslide distributions. In this study two multivariate statistical analysis methods were used （weights of evidence and logistic regression） to predict the potential distribution of shallow-seated landslides in the Kamikawachi area of Sabae City, Fukui Prefecture, Japan. First, the dependent variable （shallow-seated landslides） was divided into presence and absence, and the independent variables （environmental factors such as slope and altitude） were categorized according to their characteristics. Then, using the weights of evidence （WE） method, the weights of pairs comprising presence （w^＋（i）） or absence （w^-（i））, and the contrast values for each category of independent variable （evidence）, were calculated, Using the method that integrated the weights of evidence method and a logistic regression model, score values were calculated for each category of independent variable. Based on these contrast values, three models were selected to sum the score values of every gird in the study area. According to a receiver operating characteristic curve analysis （ROC）, model 2 yielded the best fit for predicting the potential distribution of shallow-seated landslide hazards, with 89% correctness and a 54.5% hit ratio when the occurrence probability （OP） of landslides was 70%. The model was tested using data from an area close to the study region, and showed 94% correctness and a hit ratio of 45.7% when the OP of landslides was 70%. Finally, the potential distribution of shallow-seated landslides, based on the OP, was mapped using a geographical information system. 相似文献
12.
A post flare loop system was observed on the west limb at the total solar eclipse of February 16, 1980 in Kenya. Analyzing the monochromatic images and the flash spectra, we obtained the following results: (1) the lower part of the post flare loop system is characterized mainly by distinct cool loops of H and Fe x 6374. Fe x 6374 emitting plasma (T
e = 1.0 × 106 K) is highly concentrated in the loops. The 6374 loops are broader in diameter and located very close to but a little higher than the corresponding H loops. The electron densities of the dense part in H and Fe x 6374 loops are 1011 cm-3 and 6 × 109cm-3, respectively; (2) the Ca xv emitting region (3.5 × 106 K) is confined to the upper part of the post flare loops. The electron density of this hot region is estimated as 8 × 109 cm-3 from the Ca xv line intensity ratio, I(5694)I(5445). These observational results led us to construct an empirical model of the post flare loop system which is consistent with the reconnection model of Kopp and Pneuman (1976).Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 267. 相似文献
13.
Spectrographic observations of the flash spectrum were made by the Kwasan Observatory at the total solar eclipse on 7 March, 1970. The integrated intensities of Fexiv 5303, Fex 6374, and the continuum were measured on the spectrograms as a function of height above the Sun's limb. It was found that a large amount of emission in the coronal lines originates in the interspicular regions of the chromosphere. Analysis of the data yielded that the interspicular regions consist of coronal material of T
e = 1.6 × 106–1.2 × 106 and log N
e = 8.5–9.5, and that a decrease in T
e and an increase in N
e occur with decreasing height. 相似文献
14.
Jiangtao Su Yu Liu Hiroki Kurokawa Xinjie Mao Shangbin Yang Hongqi Zhang Haimin Wang 《Solar physics》2007,242(1-2):53-63
We present new observations of the interactions of two close, but distinct, Hα filaments and their successive eruptions on
5 November 1998. The magnetic fields of the filaments are both of the sinistral type. The interactions between the two filaments
were initiated mainly by an active filament of one of them. Before the filament eruptions, two dark plasma ejections and chromospheric
brightenings were observed. They indicate that possible magnetic reconnection had occurred between the two filaments. During
the first filament eruption, salient dark mass motions transferring from the left erupting filament into the right one were
observed. The right filament erupted 40 minutes later. This second filament eruption may have been the result of a loss of
stability owing to the sudden mass injection from the left filament. Based on the Hα observations, we have created a sketch
for understanding the interactions between two filaments and accompanying activities. The traditional theory of filament merger
requires that the filaments share the same filament channel and that the reconnection occurs between the two heads, as simulated
by DeVore, Antiochos, and Aulanier (Astrophys. J.
629, 1122, 2005; 646, 1349, 2006). Our interpretation is that the external bodily magnetic reconnection between flux ropes of the same chirality is another
possible way for two filament bodies to coalesce.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
15.
16.
We propose that when all sources on the solar disc are taken into account, the S component at 10.7 cm wavelength is dominated by thermal free-free (bremsstrahlung) emission. It is not produced only in the vicinity of sunspots; more than 60% of the total flux may be due to a widely-distributed emission associated with the hot complexes of activity. Using a model for the solar atmosphere based upon an assumption of weak (or vertical) magnetic fields, the spectrum of the S-component is calculated and its sensitivity to changes in the model parameters investigated. Variation of the thicknesses of the chromosphere, transition region and mixed zone cause only small changes in the S-component spectrum; there is a much stronger dependence upon the plasma density, particularly at the base of the corona. The behaviour of the S-component at 10.7 cm wavelength is examined in more detail. We find that the largest contribution to the 10.7 cm flux originates in the low corona, that structural changes affect it only slightly, but that it is strongly density-related. This dependence upon few quantities, together with its relative localization in the low corona, contributes to the usefulness of the 10.7 cm flux as an index of solar activity.Summer Student Worker, 1988. 相似文献
17.
In an active region, several points were observed to brighten progressively on the monochromatic image of H - 1.2 Å formed by the Domeless Solar Telescope installed recently at Hida Observatory. The phenomena were interpreted as small flares or subflares. The propagation velocity was measured in two cases and discussed in terms of the multiple loop activation observed in EUV radiation.Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 249. 相似文献
18.
High-resolution observations of the flare on October 21, 1989 were made with the Domeless Solar Telescope of the Hida Observatory. The following new results have been obtained: (a) during the impulsive phase of the flare, the spectral line asymmetry has spatial fine structures of 1–2; (b) for several points in the flare region the line profile alternatively changes between blue asymmetry and red asymmetry within a few seconds. A possible explanation has been suggested. 相似文献
19.
We present a detailed study of coronal loop brightenings observed in an active region on the solar limb. These brightening loops show expanding and shrinking motions in EUV coronal line images and also show downflow along the loops in Lα and Hα images. By means of time-slice analysis of the images, we found that both the expanding and shrinking motions of the loops are not real motions of plasma but apparent motions like post-flare loops, where the loops at the different height are successively heated and cooled. From a temperature analysis, the time delay between the brightenings of hot 195 Å and cool Lα loops is found to be nearly equal to the time-scale of the conduction cooling. We conclude that these loop brightenings are sources of so called Hα coronal rains. 相似文献
20.
This study investigates the types of subaqueous deposits that occur when hot pyroclastic flows turbulently mix with water
at the shoreline through field studies of the Znp marine tephra in Japan and flume experiments where hot tephra sample interacted
with water. The Znp is a very thick, pumice-rich density current deposit that was sourced from subaerial pyroclastic flows
entering the Japan Sea in the Pliocene. Notable characteristics are well-developed grain size and density grading (lithic-rich
base, pumice-rich middle, and ash-rich top), preponderance of sedimentary lithic clasts picked up from the seafloor during
transport, fine ash depletion in coarse facies, and presence of curviplanar pumice clasts. Flume experiments provide a framework
for interpreting the origin and proximity to source of the Znp tephra. On contact of hot tephra sample with water, steam explosions
produced a gas-supported pyroclastic density current that advanced over the water while a water-supported density current
was produced on the tank floor from the base of a turbulent mixing zone. Experimental deposits comprise proximal lithic breccia,
medial pumice breccia, and distal fine ash. Experiments undertaken with cold, water-saturated slurries of tephra sample and
water did not produce proximal lithic breccias but a medial basal lithic breccia beneath an upper pumice breccia. Results
suggest the characteristics and variations in Znp facies were strongly controlled by turbulent mixing and quenching, proximity
to the shoreline, and depositional setting within the basin. Presence of abundant curviplanar pumice clasts in submarine breccias
reflects brittle fracture and dismembering that can occur during fragmentation at the vent or during quenching. Subsequent
transport in water-supported pumiceous density currents preserves the fragmental textures. Careful study is needed to distinguish
the products of subaerial versus subaqueous eruptions. 相似文献