• 천문학회지
• /
• 제36권3호
• /
• pp.105-110
• /
• 2003

Recent observations of galaxy clusters in radio and X-ray indicate that cosmic rays and magnetic fields may be energetically important in the intracluster medium. According to the estimates based on theses observational studies, the combined pressure of these two components of the intracluster medium may range between $10\%{\~}100\%$ of gas pressure, although their total energy is probably time dependent. Hence, these non-thermal components may have influenced the formation and evolution of cosmic structures, and may provide unique and vital diagnostic information through various radiations emitted via their interactions with surrounding matter and cosmic background photons. We suggest that shock waves associated with cosmic structures, along with individual sources such as active galactic nuclei and radio galaxies, supply the cosmic rays and magnetic fields to the intracluster medium and to surrounding large scale structures. In order to study 1) the properties of cosmic shock waves emerging during the large scale structure formation of the universe, and 2) the dynamical influence of cosmic rays, which were ejected by AGN-like sources into the intracluster medium, on structure formation, we have performed two sets of N-body /hydrodynamic simulations of cosmic structure formation. In this contribution, we report the preliminary results of these simulations.

• 천문학회지
• /
• 제37권5호
• /
• pp.433-438
• /
• 2004

Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. The basic properties of cluster mergers and their effects are discussed. Mergers drive shocks into the intracluster gas, and these shocks heat the intracluster gas. As a result of the impulsive heating and compression associated with mergers, there is a large transient increase in the X-ray luminosities and temperatures of merging clusters. These merger boost can affect X-ray surveys of clusters and their cosmological interpretation. Similar boosts occur in the strong lensing cross-sections and Sunyaev-Zeldovich effect in merging clusters. Merger shock and turbulence associated with mergers should also (re)accelerate nonthermal relativistic particles. As a result of particle acceleration in shocks and turbulent acceleration following mergers, clusters of galaxies should contain very large populations of relativistic electrons and ions. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these shocks will also be described. Gamma-ray observations with GLAST seem particularly promising.

• Journal of Astronomy and Space Sciences
• /
• 제30권3호
• /
• pp.133-140
• /
• 2013

Most of high energy cosmic rays (CRs) are thought to be produced by diffusive shock acceleration (DSA) at supernova remnants (SNRs) within the Galaxy. Fortunately, nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the time-dependent evolution of the self-amplified magnetic fields, Alfv$\acute{e}$nic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting nonthermal radiation spectrum. Especially, the spectral cutoffs in X-ray and ${\gamma}$-ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.

• 천문학회지
• /
• 제37권5호
• /
• pp.601-603
• /
• 2004

We present the results of the linear analysis for the Parker-Jeans instability in the magnetized gas disks including the effect of cosmic-ray diffusion along the magnetic field lines. We adopted an uni-formly rotating two temperature layered disk with a horizontal magnetic fields and solved the perturbed equations numerically. Fragmentation of gases takes place and filamentary structures are formed by the growth of the instability. Nagai et al. (1998) showed that the direction of filaments being formed by the Parker-Jeans instability depends on the strength of pressure outside the unperturbed gas disk. We found that at some range of external pressures the direction of filaments is also governed by the value of the diffusion coefficient of CR along the magnetic field lines k.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2004년도 한국우주과학회보 제13권1호
• /
• pp.100-100
• /
• 2004

Silicon Charge Detector is to measure the charge of incident cosmic-ray nuclei with a resolution of 0.2 charge unit for atomic number, Z=1-30 with energy range from 1 to 1000 TeV. It is one of detectors for CREAM (Cosmic Ray Energetics And Mass) experiment to test current models of source and acceleration mechanisms of ultra high energy cosmic rays. It's first flight will be with a NASA zero pressure balloon planned to be launched from McMurdo Station, Antarctica in December 2004. (omitted)

• 천문학회지
• /
• 제29권spc1호
• /
• pp.271-272
• /
• 1996

Assuming that particles can be accelerated to high energies via diffusive shock acceleration process at the accretion shocks formed by the infalling flow toward the clusters of galaxies, we have calculated the expected spectrum of high-energy protons from the cosmological ensemble of the cluster accretion shocks. The model with Jokipii diffusion limit could explain the observed cosmic ray spectrum near $10^{19}eV$ with reasonable parameters and models if about $10^{-4}$ of the infalling kinetic energy can be injected into the intergalactic space as the high energy particles.

• 천문학회보
• /
• 제41권1호
• /
• pp.72.4-73
• /
• 2016

For the development of magneto rotational instability, which drives mass accretion in protoplanetary disks, sufficient ionization degree is needed. Cosmic rays are believed to be one of the dominant ionization sources for protoplanetary disk gas. In previous studies, ionization rates are computed by considering the effect of attenuation of the cosmic ray (CR) intensity as a function of column density in an unmagnetized cloud. However, in reality particles should sweep up larger column density to reach at the midplane of disk due to their gyromotion. In this study, we investigate the propagation of CR protons in a protoplanetary disk by solving transport and energy loss equations. We discuss the change in CR intensity due to magnetic field in a protoplanetary disk.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 1993년도 한국우주과학회보 제2권2호
• /
• pp.10-10
• /
• 1993

The cosmic ray experiment (CRE) on board the KITSAT-1 has been operating normally since the launch of the satellite. CRE is composed of two parts : the cosmic particle experiment (CPE) and the total dose experiment (TDE). Of these, we will discuss on the CPE results obtained the last several months. The data show much larger high energy Particle flux than the Previous UOSAT-3 data. The 550(single event upset) rate is also an order of magnitude higher than the UOSAT-3result. We will compare these results with the Bredictions of the CREME codel. ReferTncesAdams, J. H., Jr., 1987, NRL Memorandun Report 5901

• 천문학회보
• /
• 제32권1호
• /
• pp.98-98
• /
• 2007

• Journal of Astronomy and Space Sciences
• /
• 제25권2호
• /
• pp.149-156
• /
• 2008

우주선 intensity가 갑작스럽게 감소하는 대표적인 현상인 Forbush Decrease(FD)는 행성간 충격파(Interplanetary shock), 자기 구름(Magnetic cloud)과 같은 태양풍 이벤트와 밀접한 관련성을 가지고 있다. FD 현상에 대해 태양풍 이벤트 중 자기구름이 어느 정도 효과적으로 작용하는 지에 대해 알아보기 위해 1998-1999년의 2년 동안 발생한 44개의 자기 구름을 분석하였다. 그 결과 44개 중 11개의 자기 구름이 FD 현상과 관련이 있었으며, 자기 구름 영역이나 자기구름과 관계된 행성간 충격파의 sheath 영역의 평균 자기장 세기, 자기장 교란도 그리고 태양풍 속도와 같은 행성간 자기장 및 태양풍의 물리적 특성이 FD 현상과의 관련성을 대표해준다는 것을 밝혀냈다. 특히, 행성간 충격파 sheath 영역의 자기장 및 태양풍의 물리량이 자기장 세기가 13nT, 자기장 교란도는 3nT, 및 태양풍 속도가 평균 550km/s 이상의 태양풍 이벤트에서 FD 발생에 효과적으로 작용하는 것으로 분석되었다.