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31.
Morphological and evolutional features of Ellerman bombs were studied with H filtergrams of two active regions very close to the solar limb. We quantitatively determined the elongated or spike-like shape of the bomb. The mean apparent length of 174 bombs is 1.1 arc sec, while 80% of 204 bombs have a diameter of less than 0.6 arc sec. The mean lifetime of 77 bombs is about 12 min at H - 1.2 Å. The first maximum brightness of a typical bomb is attained, on average in about 2 min. Bombs grow longer in the first brightening phase and their mean upward velocity explains the blue asymmetry of H emission profiles of moustaches. 相似文献
32.
Yuki Sugahara Masahumi Kawaguchi Tatsuya Itoyama Daisuke Kurokawa Yasuhiko Tosa Shin-Ichi Kitamura Itsuki C. Handoh Kei Nakayama Yasunori Murakami 《Marine pollution bulletin》2014
Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T. niphobles). Larvae exposed to pyrene or phenanthrene exhibited no abnormalities in morphology. However, those exposed to pyrene but not phenanthrene swam in an uncoordinated manner, although their swimming distance and speed were normal. The optic tectum, a part of the midbrain, of pyrene-exposed larvae did not grow to full size. Thus, these findings are indicated that pyrene might be a contributor to the behavioral and neuro-developmental toxicity, although there is no indication that it is the only compound participating in the toxicity of the heavy oil mixture. 相似文献
33.
A great 3B flare, whose X-ray class was X13, occurred over a delta-sunspot at 00: 01 UT on April 25, 1984. Before the flare, a strong magnetic shear was found to be formed along the neutral line in the delta-sunspot with shear motions of umbrae. The shear motions of the umbrae were caused by the successive emergence of a magnetic flux rope.Before the flare, several groups of sheared H threads and filaments were found to merge into an elongated filament along the neutral line through the delta-sunspot. In the merging process the helical twists were formed in the filament by the reconnection as in the Pneuman's (1983) model.At the post-maximum phase of the flare, the helically twisted filament spouted out with an untwisting rotation. Examining the morphological and dynamical features of the filament eruption, we concluded that it has some typical features of the flare spray and that it seems to be accelerated by the sweeping-magnetictwist mechanism proposed by Shibata and Uchida (1986).Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 276. 相似文献
34.
H. Kurokawa T. Kitahara Y. Nakai Y. Funakoshi K. Ichimoto 《Astrophysics and Space Science》1986,118(1-2):149-152
We studied the evolutional characteristics of fine structures in H flare emitting regions and their relation to X-ray and microwave emissions for selected events observed with the 60 cm Domeless Solar Telescope at Hida Observatory, University of Kyoto. The principal conclusions of this investigation are: (1) H kernel consists of some finer bright points or Hflare points whose individual size is less than 1 arc sec. (2) Impulsive brightnenings of H flare points occurred simultaneously with the spikes of the hard X-ray and microwave bursts within the time resolution of our H observations which varied from 1 to 10 s. (3) It is concluded that fast electron beams must be the principal mechanism of heating H flares during the impulsive phase of a flare.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 265. 相似文献
35.
Hiroki Kurokawa 《Solar physics》1975,43(2):385-403
The flash spectrograms obtained at the June 30, 1973 eclipse contain the monochromatic images of a coronal condensation in three coronal lines of Fexiv 5303, Fex 6374 and Fexi 7892 and Hα line. The assumption of the axially-symmetric distribution of the emissivity in the coronal lines allows us to find the density and temperature structure of the coronal condensation. While the electron density in the central axis of the condensation is about ten times as high as that of the normal corona at each height, the temperature is not so high (T?2.3×106K). This seems to be a representative nature of a coronal active region in the post maximum phase of activity. It is found that there exists a cool and dense core (T = 106K, N e =6 × 109 cm-3 at 17000 km) at the lower part of the coronal condensation, which is in a close geometrical coincidence with the small active prominence protruding from the underlying plage region. 相似文献
36.
L. Van Driel-Gesztelyi B. Schmieder G. Cauzzi N. Mein A. Hofmann N. Nitta H. Kurokawa P. Mein J. Staiger 《Solar physics》1996,163(1):145-170
Ground-based optical observations coordinated with Yohkoh/SXT X-ray observations of an old, disintegrating bipolar active region AR NOAA 7493 (May 1, 1993) provided a multiwavelength data base to study a flaring active region X-ray bright point (XBP) of about 16 hr lifetime, and the activity related to it in different layers of the solar atmosphere. The XBP appeared to be related to a new minor bipole of about 1020 Mx. Superposed on a global evolution of soft X-ray brightness, the XBP displayed changes of brightness, lasting for 1–10 min. During the brightenings the XBP apparently had a spatial structure, which was (tiny) loop-like rather than point-like. The X-ray brightenings were correlated with chromospheric activity: (i) brightenings of underlying chromospheric faculae, and (ii) appearance of strong turbulent velocities in the arch filament system. We propose that the XBP brightenings were due to reconnection of the magnetic field lines (sketched in 3D) between the new bipole and a pre-existing plage field induced by the motion of one of the new pores (v = 0.2 km s–1) towards the plage, and that the XBP itself was a reconnected hot loop between them. 相似文献
37.
In this paper, we analyze the relations between photospheric vector magnetic fields, chromospheric longitudinal magnetic fields and velocity fields in a solar active region. Agreements between the photospheric and chromospheric magnetograms can be found in large-scale structures or in the stronger magnetic structures, but differences also can be found in the fine structures or in other places, which reflect the variation of the magnetic force lines from the photosphere to the chromosphere. The chromospheric superpenumbral magnetic field, measured by the Hline, presents a spoke-like structure. It consists of thick magnetic fibrils which are different from photospheric penumbral magnetic fibrils. The outer superpenumbral magnetic field is almost horizontal. The direction of the chromospheric magnetic fibrils is generally parallel to the transverse components of the photospheric vector magnetic fields. The chromospheric material flow is coupled with the magnetic field structure. The structures of the H chromospheric magnetic fibrils in the network are similar to H dark fibrils, and the feet of the magnetic fibrils are located at the photospheric magnetic elements. 相似文献
38.
Shigenori Maruyama Ken Kurokawa Toshikazu Ebisuzaki Yusuke Sawaki Konomi Suda M.Santo 《地学前缘(英文版)》2019,10(4):1337-1357
The origin of life on Earth remains enigmatic with diverse models and debates.Here we discuss essential requirements for the first emergence of life on our planet and propose the following nine requirements:(1)an energy source(ionizing radiation and thermal energy);(2)a supply of nutrients(P.K.REE.etc.);(3)a supply of life-constituting major elements;(4)a high concentration of reduced gases such as CH_4,HCN and NH_3;(5)dry-wet cycles to create membranes and polymerize RNA;(6)a non-toxic aqueous environment;(7)Na-poor water;(8)highly diversified environments,and(9)cyclic conditions,such as dayto-night,hot-to-cold etc.Based on these nine requirements,we evaluate previously proposed locations for the origin of Earth's life,including:(1)Darwin's "warm little pond",leading to a "prebiotic soup" for life;(2)panspermia or Neo-panspermia(succession model of panspermia);(3)transportation from/through Mars;(4)a deepsea hydrothermal system;(5)an on-land subduct ion-zone hot spring,and(6)a geyser systems driven by a natural nuclear reactor.We conclude that location(6)is the most ideal candidate for the o rigin point for Earth's life because of its efficiency in continuously supplying both the energy and the necessary materials for life,thereby maintaining the essential "cradle" for its initial development.We also emphasize that falsifiable working hypothesis provides an important tool to evaluate one of the biggest mysteries of the universe-the origin of life. 相似文献
39.
Yun‐Guo Liu Tadahide Kurokawa Masashi Sekino Toru Tanabe Kazuhito Watanabe 《Marine Ecology》2014,35(3):273-280
We found that tandem repeat (TR) arrays were present in the ark shell Scapharca broughtonii mitochondrial genome, and we demonstrated the efficiency of using this TR region as a tool for the detection of genetic differentiation. In samples collected from seven populations off the Japanese, Chinese, Russian and Korean coasts, five TR types with length ranging from 481 to 601 bp (base pairs) were found, as were 18 haplotypes (n = 155). All the Japanese samples from SD, IK, AM and KG, which represented four geographically distinct populations, had the same type of tandem repeat array, 481‐TR. All the samples from China and all but one sample from Russia had the same TR type, 511‐TR; these finding may be strong evidence that the ark shell populations in China and Russia are very similar. Based on a neighbor‐joining dendrogram of haplotypes, the Korean population was divided into two groups as follows: samples with haplotype H481‐3 and samples with haplotypes H601‐1, H601‐2, H601‐3 or H541‐1. Based on the haplotype diversity and nucleotide diversity, the Chinese, Russian and Korean populations showed a higher diversity than Japanese populations (P < 0.05). 相似文献