Importance of Prolate Neutrino Radiation in Core-Collapse Supernovae: The Reason for the Prolate Geometry of SN1987A?

We have carried out 2-D simulations of core-collapse supernova explosions. The local neutrino radiation field is assumed to have its maximum value either at the symmetry (polar) axis or on the equatorial plane. These lead to the prolate and oblate explosions, respectively. We find that the gain of the explosion energy in the prolate explosion evolves more predominately than that in the oblate one when the total neutrino luminosity is given. Namely, the prolate explosion is more energetic than the oblate one. One of the authors (Shimizu et al. 2001) showed for the first time that globally anisotropic neutrino radiation produces more powerful explosion than the spherical neutrino radiation does. In our previous study (Madokoro et al. 2003), we improved the numerical code of Shimizu et al. and demonstrated that the globally anisotropic neutrino radiation yields more energetic explosion than spatially-fluctuated neutrino radiation does. Together with the result of this paper, we conclude that the globally anisotropic (prolate) neutrino radiation is the most effective way of increasing the explosion energy among various types of explosions investigated in these studies. We discuss the reason for this. Our result is suggestive of the fact that the expanding materials of SN1987A is observed to have a prolate geometry.Comment: 15 pages, including 7 figures, to appear in PAS

チュウブニホンイナダニニオケルヒョウガサヨウダンキュウケイセイトチケイ

京都大学0048新制・論文博士理学博士乙第1577号論理博第305号新制||理||121(附属図書館)2555UT51-45-L249(主査)教授 亀井 節夫, 教授 中沢 圭二, 教授 吉沢 甫学位規則第5条第2項該当Kyoto UniversityDA

Significance of the Ikenotaira Interstadial Indicated by Moraines on Mt. Kumazawa of the Kiso Mountain Range, Central Japan

From tephra cover on the outermost moraine in the Ikenotaira cirque on Mt. Kumazawa of the Kiso mountain range, a small amount of air-borne scoria from Ontake volcano was collected. The scoria is identified with that of the scoria-fall deposit Sc-I which within the section of the air-laid Younger tephra unit of the so-called Shinshu Loam Formation lies in the basal part. The radiometric age of the Kisogawa volcanic mudflow associated with the Sc-I approximates 27,0001t C years ago, indicating that the outermost moraine be assigned to the pre-Paudorf glacial stade, whereas the upper two moraines should postdate the Paudorf interstadial. The interval indicated between the lower two moraines is emphasized to establish the Late Quaternary chronology. The date of the Ikenotaira interstadial also supports that simultaneous uprise of sea level may have taken place.Article信州大学理学部紀要 1(2): 97-113(1967)departmental bulletin pape

Pleistocene Tephras in the Northern Part of Ina Valley, Central Japan

ArticleJournal of the Faculty of Liberal Arts and Science, Shinshu University. Part 2, Natural science 12: 20-45(1962)departmental bulletin pape

Classification and Correlation of Shin shu Loam in the South Shinshu Tephrogenetic Region, Central Japan

This is a preliminary report of somewhat an essential part of tephrochronological study mainly made in the Ina valley since the last publication of our paper (KOBAYASHI and SHIMIZU, 1962). Tephrochronological study thus being carried in this district and its environs presents for further studies such many clues as micro- and mega-fossil flora closely associated with tephra horizons. These clues may permit us to get detail chronological and climatological informations from the Quaternary events in these districts. Our study has been advanced through only stratigraphic works, except for a few radiocarbon dates obtained from very limited samples. The purpose of the present paper includes the presentation of a chronological base for further studies. Anyhow, it is stressed from our study that no indications of warmer climate have been detected within a sequence of deposits younger than the period when the Wakamiko-Shinmachi plant beds were deposited. Additionally, the Pm-I has well been traced into the Shimosueyoshi Loam which conformably covers the surface of the Shimosueyoshi formation-a transgressive deposit (KOBAYASHI, 1965 a, b). Hence, the Shimosueyoshi marine transgression should be understood as the last major transgression having occurred during Pleistocene time. Exact stratigraphic situation of the Older Loam unit has remaind for future studies, owing to a few exposures and an intensive weathering of primary minerals contained in it. We have obligations to record kind helps offerred by two geobotanists, Dr. K. SUZUKI, Department of Geology, Fukushima University, and Dr. S. KOKAWA, Department of Botany, Osaka City University. We are also indebted to Mr. Y. GOHARA of our Department of Geology, and to Dr. S. KAWACHI, Mr. T. KOBAYASHI, Mr. K. KITAZAWA, and Mr. T. NASU for their cooperation.ArticleJournal of the Faculty of Liberal Arts and Science, Shinshu University. Part 2, Natural science 15: 37-59(1965)departmental bulletin pape

Core-Collapse Supernovae Induced by Anisotropic Neutrino Radiation

We demonstrate the important role of anisotropic neutrino radiation on the mechanism of core-collapse supernova explosions. Through a new parameter study with a fixed radiation field of neutrinos, we show that prolate explosions caused by globally anisotropic neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This is suggestive of the fact that the expanding materials of SN 1987A has a prolate geometry.Comment: in Proceedings of Int. conf. in hohour of the 60th birthday of Marcel Arnould, The Future Astronuclear Physics, From microscopic puzzles to macroscopic nightmares, Eds. H.M.J. Boffin et al., EAS Publication Series, EDP Sciences, in press (2004