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Ionization of protoplanetary disks by galactic cosmic rays,solar protons,and supernova remnants

Geoscience Frontiers 2017年第2期8卷 247-252页

作者： Ryuho Kataoka tatsuhiko sato National Institute of Polar Research 10-3 Midori-choTachikawaTokyo190-8513Japan SOKENDAI 10-3 Midori-choTachikawaTokyo190-8513Japan Japan Atomic Energy Agency Shirakata 2-4TokaiIbaraki319-1195Japan

Galactic cosmic rays and solar protons ionize the present terrestrial atmosphere,and the air showers are simulated by well-tested Monte-Carlo simulations,such as PHITS *** use the latest version of PHITS to evaluate the possible ionization of protoplanetary disks by galactic cosmic rays（GCRs）,solar protons,and by supernova *** attenuation length of GCR ionization is updated as 118 g cm^-2,which is approximately 20% larger than the popular *** and soft possible spectra of solar protons give comparable and 20% smaller attenuation lengths compared with those from standard GCR spectra,respectively,while the attenuation length is approximately 10% larger for supernova ***,all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance,e.g.128 g cm^-2 for GCRs,which can affect the minimum estimate of the size of dead zones in protoplanetary disks when the incident flux is unusually high.

关键词： Galactic cosmic rays Solar protons Supernova remnants Young Sun Protoplanetary disk T Tauri stars

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Direct Simulation Methods for Scalar-Wave Envelopes in Two-Dimensional Layered Random Media Based on the Small-Angle Scattering Approximation

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Communications in Computational Physics 2008年第1期3卷 63-84页

作者： tatsuhiko Saito Haruo sato Tsutomu Takahashi Earthquake Research Institute The University of TokyoYayoi 1-1-1Bunkyo-kuTokyo113-0032Japan. CREST Japan Science and Technology Agency(JST). Department of Geophysics Graduate School of ScienceTohoku UniversityAramaki-Aza-Aoba 6-3Aoba-kuSendaiMiyagi980-8578Japan. Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and TechnologyShowa-machi 3173-25Kanazawa-kuYokohamaKanagawa236-0001Japan.

This study presents stochastic methods to simulate wave envelopes in layeredrandom media. High-frequency Seismograms of small earthquakes are so complexdue to lithospheric inhomogeneity that seismologists often analyze wave envelopesrather than wave traces to quantify the subsurface inhomogeneity. Since thestatistical properties of the inhomogeneity vary regionally, it is important to developand examine direct envelope simulation methods for non-uniform random media. Asa simple example, this study supposes planewave propagation through two-layer randommedia in 2-D composed of weak and strong inhomogeneity zones. The characteristicspatial-scale of the inhomogeneity is supposed to be larger than the wavelength,where small-angle scattering around the forward direction dominates large-angle *** envelope simulation methods based on the small-angle scattering approximationare examined. One method is to solve a differential equation for the twofrequencymutual coherence function with the Markov approximation. The other isto solve the stochastic ray bending process by using the Monte Carlo method basedon the Markov approximation for the mutual coherence function. The resultant waveenvelopes of the two methods showed excellent coincidence both for uniform and fortwo-layer random media. Furthermore, we confirmed the validity of the two methodscomparing with the envelopes made from the finite difference simulations of *** two direct envelope simulation methods presented in this study can be a mathematicalbase for the study of high-frequency wave propagation through randomlyinhomogeneous lithosphere in seismology.

关键词： Seismic wave envelope random media.

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