Jongsoo Kim - KASI, Korea

Jongsoo Kim
Are you Jongsoo Kim?

Claim your profile, edit publications, add additional information:

Contact Details

Name
Jongsoo Kim
Affiliation
KASI, Korea
City
Seogwipo-si
Country
South Korea

Pubs By Year

External Links

Pub Categories

 
Astrophysics (27)
 
Astrophysics of Galaxies (15)
 
Instrumentation and Methods for Astrophysics (9)
 
High Energy Astrophysical Phenomena (2)
 
Solar and Stellar Astrophysics (1)
 
Cosmology and Nongalactic Astrophysics (1)

Publications Authored By Jongsoo Kim

2017Apr
Authors: Derek Ward-Thompson, Kate Pattle, Pierre Bastien, Ray S. Furuya, Woojin Kwon, Shih-Ping Lai, Keping Qiu, David Berry, Minho Choi, Simon Coudé, James Di Francesco, Thiem Hoang, Erica Franzmann, Per Friberg, Sarah F. Graves, Jane S. Greaves, Martin Houde, Doug Johnstone, Jason M. Kirk, Patrick M. Koch, Jungmi Kwon, Chang Won Lee, Di Li, Brenda C. Matthews, Joseph C. Mottram, Harriet Parsons, Andy Pon, Ramprasad Rao, Mark Rawlings, Hiroko Shinnaga, Sarah Sadavoy, Sven van Loo, Yusuke Aso, Do-Young Byun, Eswariah Chakali, Huei-Ru Chen, Mike C. -Y. Chen, Wen Ping Chen, Tao-Chung Ching, Jungyeon Cho, Antonio Chrysostomou, Eun Jung Chung, Yasuo Doi, Emily Drabek-Maunder, Stewart P. S. Eyres, Jason Fiege, Rachel K. Friesen, Gary Fuller, Tim Gledhill, Matt J. Griffin, Qilao Gu, Tetsuo Hasegawa, Jennifer Hatchell, Saeko S. Hayashi, Wayne Holland, Tsuyoshi Inoue, Shu-ichiro Inutsuka, Kazunari Iwasaki, Il-Gyo Jeong, Ji-hyun Kang, Miju Kang, Sung-ju Kang, Koji S. Kawabata, Francisca Kemper, Gwanjeong Kim, Jongsoo Kim, Kee-Tae Kim, Kyoung Hee Kim, Mi-Ryang Kim, Shinyoung Kim, Kevin M. Lacaille, Jeong-Eun Lee, Sang-Sung Lee, Dalei Li, Hua-bai Li, Hong-Li Liu, Junhao Liu, Sheng-Yuan Liu, Tie Liu, A-Ran Lyo, Steve Mairs, Masafumi Matsumura, Gerald H. Moriarty-Schieven, Fumitaka Nakamura, Hiroyuki Nakanishi, Nagayoshi Ohashi, Takashi Onaka, Nicolas Peretto, Tae-Soo Pyo, Lei Qian, Brendan Retter, John Richer, Andrew Rigby, Jean-François Robitaille, Giorgio Savini, Anna M. M. Scaife, Archana Soam, Motohide Tamura, Ya-Wen Tang, Kohji Tomisaka, Hongchi Wang, Jia-Wei Wang, Anthony P. Whitworth, Hsi-Wei Yen, Hyunju Yoo, Jinghua Yuan, Chuan-Peng Zhang, Guoyin Zhang, Jianjun Zhou, Lei Zhu, Philippe André, C. Darren Dowell, Sam Falle, Yusuke Tsukamoto

We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope (JCMT) in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions which the survey will aim to answer. Read More

Class I methanol masers are found to be good tracers of the interaction between outflows from massive young stellar objects with their surrounding media. Although polarization observations of Class II methanol masers have been able to provide information about magnetic fields close to the central (proto)stars, polarization observations of Class I methanol masers are rare, especially at 44 and 95 GHz. We present the results of linear polarization observations of 39 Class I methanol maser sources at 44 and 95 GHz. Read More

The East-Asian VLBI Network (EAVN) is the international VLBI facility in East Asia and is conducted in collaboration with China, Japan, and Korea. The EAVN consists of VLBI arrays operated in each East Asian country, containing 21 radio telescopes and three correlators. The EAVN will be mainly operated at 6. Read More

CIT 6 is a carbon star in the transitional phase from the asymptotic giant branch (AGB) to the protoplanetary nebulae (pPN). Observational evidences of two point sources in the optical, circumstellar arc segments in an HC$_3$N line emission, and a bipolar nebula in near-infrared provide strong support for the presence of a binary companion. Hence, CIT 6 is very attractive for studying the role of companions in the AGB-pPN transition. Read More

2015Jul
Affiliations: 1KASI, Korea, 2KASI, Korea, 3KASI, Korea, 4KASI, Korea, 5KASI, Korea, 6KASI, Korea, 7KASI, Korea, 8KASI, Korea, 9KASI, Korea, 10KASI, Korea

We report results of investigation of amplitude calibration for very long baseline interferometry (VLBI) observations with Korean VLBI Network (KVN). Amplitude correction factors are estimated based on comparison of KVN observations at 22~GHz correlated by Daejeon hardware correlator and DiFX software correlator in Korea Astronomy and Space Science Institute (KASI) with Very Long Baseline Array (VLBA) observations at 22~GHz by DiFX software correlator in National Radio Astronomy Observatory (NRAO). We used the observations for compact radio sources, 3C 454. Read More

We carry out three-dimensional hydrodynamic simulations of the supernova remnants (SNRs) produced inside molecular clouds (MCs) near their surface using the HLL code (Harten et al. 1983). We explore the dynamical evolution and the X-ray morphology of SNRs after breaking through the MC surface for ranges of the explosion depths below the surface and the density ratios of the clouds to the intercloud media (ICM). Read More

2015Mar
Affiliations: 1KASI, Korea, 2KASI, Korea, 3KASI, Korea, 4KASI, Korea, 5KASI, Korea, 6KASI, Korea, 7KASI, Korea, 8KASI, Korea, 9KASI, Korea, 10KASI, Korea, 11SHAO, China, 12NAOJ, Japan, 13KASI, Korea

We report results of the performance evaluation of a new hardware correlator in Korea, the Daejeon correlator, developed by the Korea Astronomy and Space Science Institute (KASI) and the National Astronomical Observatory of Japan (NAOJ). We conducted Very Long Baseline Interferometry (VLBI) observations at 22~GHz with the Korean VLBI Network (KVN) in Korea and the VLBI Exploration of Radio Astrometry (VERA) in Japan, and correlated the aquired data with the Daejeon correlator. For evaluating the performance of the new hardware correlator, we compared the correlation outputs from the Daejeon correlator for KVN observations with those from a software correlator, the Distributed FX (DiFX). Read More

We investigate the power spectra of outflow-driven turbulence through high-resolution three-dimensional isothermal numerical simulations where the turbulence is driven locally in real-space by a simple spherical outflow model. The resulting turbulent flow saturates at an average Mach number of ~2.5 and is analysed through density and velocity power spectra, including an investigation of the evolution of the solenoidal and compressional components. Read More

Oxygen-rich Asymptotic Giant Branch (AGB) stars can be intense emitters of SiO ($v$=1 and 2, J=1$\rightarrow$0) and H$_2$O maser lines at 43 and 22 GHz, respectively. VLBI observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned \water\ and $v$=1 and $v$=2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. Read More

We present the results of unbiased 22 GHz H2O water and 44 GHz class I CH3OH methanol maser surveys in the central 7x10 arcmin area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ~3x3arcmin area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with sensitivity of sigma~0.3Jy, we confirmed masers toward H2O(B) in the region of HH 7-11 and IRAS4B. Read More

The Korean VLBI Network (KVN) is a new mm-VLBI dedicated array with capability for simultaneous observations at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well established instrument. Read More

The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23 and 43 GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M 87. Read More

We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds x 1. Read More

2014Feb
Affiliations: 1Huazhong University of Science and Technology, China, 2Korea Astronomy and Space Science Institute, Korea, 3Chungnam National University, Korea

Wu et al. (2009) suggested an empirical relation between the magnetic field strength along the line of sight (LOS) and the dispersion of Faraday rotation measure (RM) distribution in turbulent media with root-mean-square sonic Mach number $M_s \simeq 1$. In this paper, we extend the work by incorporating the Mach number dependence. Read More

(Abridged). We present numerical simulations of isothermal, MHD, supersonic turbulence, designed to test various hypotheses frequently assumed in star formation(SF) theories. We consider three simulations, each with a different combination of physical size, rms sonic Mach number, and Jeans parameter, but chosen as to give the same value of the virial parameter and to conform with Larson's scaling relations. Read More

Protostellar jets and outflows are signatures of star formation and promising mechanisms for driving supersonic turbulence in molecular clouds. We quantify outflow-driven turbulence through three-dimensional numerical simulations using an isothermal version of the robust total variation diminishing code. We drive turbulence in real-space using a simplified spherical outflow model, analyse the data through density probability distribution functions (PDF), and investigate the Core Formation Rate per free-fall time (CFR_ff). Read More

We study the Faraday rotation measure (RM) due to the Galactic magnetic field (GMF) toward high Galactic latitudes. The RM arises from the global, regular component as well as from the turbulent, random component of the GMF. We model the former based on observations and the latter using the data of magnetohydrodynamic turbulence simulations. Read More

We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function (Sigma-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50pc. At low densities (n <= 0. Read More

This paper presents the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 623 sources have not been observed before at Q-band with VLBI. The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22-129 GHz and to build a list of objects that can be used as targets and as calibrators. Read More

We performed a numerical experiment designed for core formation in a self-gravitating, magnetically supercritical, supersonically turbulent, isothermal cloud. A density probability distribution function (PDF) averaged over a converged turbulent state before turning self-gravity on is well-fitted with a lognormal distribution. However, after turning self-gravity on, the volume fractions of density PDFs at a high density tail, compared with the lognormal distribution, increase as time goes on. Read More

In this paper we numerically study the behavior of the density power spectrum in turbulent thermally bistable flows. We analyze a set of five three-dimensional simulations where turbulence is randomly driven in Fourier space at a fixed wave-number and with different Mach numbers M (with respect to the warm medium) ranging from 0.2 to 4. Read More

2009Oct
Affiliations: 1Korea Astronomy and Space Science Institute, 2Korea Astronomy and Space Science Institute, 3Chungnam National University, Korea, 4Chungnam National University, Korea, 5Cambridge University, UK

We studied Faraday rotation measure (RM) in turbulent media with the rms Mach number of unity, using isothermal, magnetohydrodynamic turbulence simulations. Four cases with different values of initial plasma beta were considered. Our main findings are as follows. Read More

We calculate the evolution of molecular line profiles of HCO$^+$ and C$^{18}$O toward a dense core thatis forming inside a magnetized turbulent molecular cloud. Features of the profiles can be affected more significantly by coupled velocity and abundance structures in the outer region than those in the inner dense part of the core. The velocity structure at large radii is dominated by a turbulent flow nearby and accretion shocks onto the core, which resulting in the variation between inward and outward motions during the evolution of the core. Read More

We describe a method for incorporating ambipolar diffusion in the strong coupling approximation into a multidimensional magnetohydrodynamics code based on the total variation diminishing scheme. Contributions from ambipolar diffusion terms are included by explicit finite difference operators in a fully unsplit way, maintaining second order accuracy. The divergence-free condition of magnetic fields is exactly ensured at all times by a flux-interpolated constrained transport scheme. Read More

2008Aug
Affiliations: 1CEA/Saclay, 2CfA/Harvard, 3KASI, 4UNAM/Morelia
Category: Astrophysics

In this paper, we review some of the properties of dense molecular cloud cores. The results presented here rely on three-dimensional numerical simulations of isothermal, magnetized, turbulent, and self-gravitating molecular clouds (MCs) in which dense core form as a consequence of the gravo-turbulent fragmentation of the clouds. In particular we discuss issues related to the mass spectrum of the cores, their lifetimes and their virial balance. Read More

2008Jun
Affiliations: 1Astrophysical Research Center for the Structure and Evolution of the Cosmos, 2International Center for Astrophysics, Korea Astronomy and Space Science Institute, 3International Center for Astrophysics, Korea Astronomy and Space Science Institute
Category: Astrophysics

High-resolution SiO observations of the NGC 1333 IRAS 4A star-forming region showed a highly collimated outflow with a substantial deflection. The deflection was suggested to be caused by the interactions of the outflow and a dense cloud core. To investigate the deflection process of protostellar outflows, we have carried out three-dimensional hydrodynamic simulations of the collision of an outflow with a dense cloud. Read More

We present three numerical simulations of randomly driven, isothermal, non-magnetic, self-gravitating turbulence with different rms Mach numbers Ms and physical sizes L, but approximately the same value of the virial parameter, alpha approx 1.2. We obtain the following results: a) We test the hypothesis that the collapsing centers originate from locally Jeans-unstable ("super-Jeans"), subsonic fragments; we find no such structures. Read More

2008Mar
Affiliations: 1Seoul National University, 2Seoul National University, 3Seoul National University, 4Korea Astronomy and Space Science Institute
Category: Astrophysics

We explore tidal interactions of a galactic disk with Toomre parameter Q ~ 2 embedded in rigid halo/bulge with a point mass companion moving in a prescribed parabolic orbit. Tidal interactions produce well-defined spiral arms and extended tidal features such as bridge and tail that are all transient, but distinct in nature. In the extended disks, strong tidal force is able to lock the perturbed epicycle phases of the near-side particles to the perturber, shaping them into a tidal bridge that corotates with the perturber. Read More

2008Jan
Affiliations: 1CEA Saclay, 2NORDITA, 3KASI, 4KASI, 5Lebanese U
Category: Astrophysics

We analyze the mass distribution of cores formed in an isothermal, magnetized, turbulent, and self-gravitating nearly critical molecular cloud model. Cores are identified at two density threshold levels. Our main results are that the presence of self-gravity modifies the slopes of the core mass function (CMF) at the high mass end. Read More

We present a model to explain the mass segregation and shallow mass functions observed in the central parts of dense and young starburst stellar clusters. The model assumes that the initial pre-stellar cores mass function resulting from the turbulent fragmentation of the proto-cluster cloud is significantly altered by the cores coalescence before they collapse to form stars. With appropriate, yet realistic parameters, this model based on the competition between cores coalescence and collapse reproduces the mass spectra of the well studied Arches cluster. Read More

2007Jun

We investigate the time evolution of the mass distribution of pre-stellar cores (PSCs) and their transition to the initial stellar mass function (IMF) in the central parts of a molecular cloud (MC) under the assumption that the coalescence of cores is important. Our aim is to explain the observed shallow IMF in dense stellar clusters such as the Arches cluster. The initial distributions of PSCs at various distances from the MC center are those of gravitationally unstable cores resulting from the gravo-turbulent fragmentation of the MC. Read More

2007Apr
Affiliations: 1Centro de Radioastronomía y Astrofísica. UNAM, 2Centro de Radioastronomía y Astrofísica. UNAM, 3Korea Astronomy and Space Science Institute, 4Centro de Radioastronomía y Astrofísica. UNAM, 5Korea Astronomy and Space Science Institute
Category: Astrophysics

We present measurements of the mean dense core lifetimes in numerical simulations of magnetically supercritical, turbulent, isothermal molecular clouds, in order to compare with observational determinations. "Prestellar" lifetimes (given as a function of the mean density within the cores, which in turn is determined by the density threshold n_thr used to define them) are consistent with observationally reported values, ranging from a few to several free-fall times. We also present estimates of the fraction of cores in the "prestellar", "stellar'', and "failed" (those cores that redisperse back into the environment) stages as a function of n_thr. Read More

We investigate, in a set of 3D numerical simulations of driven, magnetized, isothermal, and self-gravitating molecular clouds (MCs), the statistical correlations between the energy ratios (thermal/gravity, and kinetic/gravity) of clumps and cores (CCs) identified in the simulations and gravitational binding indicators commonly used in observational studies such as the Jeans number, J_{c}, and the virial parameter, alpha_{vir}. In the energy ratios, we consider the surface energy terms which account for the effects of the environment on the clump gravitational boundedness. We find that: a) J_{c} and the thermal/gravitational energy ratios are well correlated, b) alpha_{vir} and the (thermal+kinetic)/gravity or kinetic/gravity energy ratios are poorly correlated, additionally affected by the ambiguity of the compressive or dispersive effect of the velocity field. Read More

2006Jul

We study the instantaneous virial balance of clumps and cores (CCs) in 3D simulations of driven, MHD, isothermal molecular clouds (MCs). The models represent a range of magnetic field strengths in MCs from subcritical to non-magnetic regimes. We identify CCs at different density thresholds, and for each object, we calculate all the terms that enter the Eulerian form of the virial theorem (EVT). Read More

2006Apr
Affiliations: 1Sejong University, Korea, 2Chungnam National University, Korea, 3Pusan National University, Korea, 4Korea Astronomy & Space Science Institute
Category: Astrophysics

Thermal-gravitational instability (TGI) is studied in the protogalactic environment. We extend our previous work, where we found that dense clumps first form out of hot background gas by thermal instability and later a small fraction of them grow to virialized clouds of mass M_c >~ 6X10^6 M_sun by gravitational infall and merging. But these clouds have large angular momentum, so they would be difficult, if not impossible, to further evolve into globular clusters. Read More

2005Sep
Affiliations: 11=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 21=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 31=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 41=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 51=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 61=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam, 71=Centro de Radioastronomía y Astrofísica, UNAM, 2=Korea Astronomy and Space Science Institute, 3=Astrophysikalisches Institut Potsdam
Category: Astrophysics

We investigate the core mass distribution (CMD) resulting from numerical models of turbulent fragmentation of molecular clouds. In particular we study its dependence on the sonic root-mean-square Mach number $\Ms$. We analyze simulations with $\Ms$ ranging from 1 to 15 to show that, as $\Ms$ increases, the number of cores increases as well while their average mass decreases. Read More

2005Jul
Affiliations: 1Centro de Radioastronomia y Astrofisica, UNAM, Mexico;, 2Korea Astronomy and Space Science Institute, 3Centro de Radioastronomia y Astrofisica, UNAM, Mexico;
Category: Astrophysics

We present measurements of the star formation efficiency (SFE) in 3D numerical simulations of driven turbulence in supercritical, ideal-MHD, and non-magnetic regimes, characterized by their mean normalized mass-to-flux ratio $\mu$, all with 64 Jeans masses and similar rms Mach numbers ($\sim 10$). In most cases, the moderately supercritical runs with $\mu = 2.8$ have significantly lower SFEs than the non-magnetic cases, being comparable to observational estimates for whole molecular clouds ($\lesssim$ 5% over 4 Myr). Read More

2005Jul
Affiliations: 1Korea Astronomy and Space Science Institute, 2Chungman National University, Korea
Category: Astrophysics

Turbulent flows are ubiquitous in astrophysical environments, and understanding density structures and their statistics in turbulent media is of great importance in astrophysics. In this paper, we study the density power spectra, $P_{\rho}$, of transonic and supersonic turbulent flows through one and three-dimensional simulations of driven, isothermal hydrodynamic turbulence with root-mean-square Mach number in the range of $1 \la M_{\rm rms} \la 10$. From one-dimensional experiments we find that the slope of the density power spectra becomes gradually shallower as the rms Mach number increases. Read More

2005Jun
Affiliations: 1Pusan National University, Korea, 2Pusan National University, Korea, 3Korea Astronomy & Space Science Institute, 4Chungnam National University, Korea
Category: Astrophysics

We study thermal-gravitational instability in simplified models for protogalactic halos using three-dimensional hydrodynamic simulations. The simulations followed the evolution of gas with radiative cooling down to T = 10^4 K, background heating, and self-gravity. Then cooled and condensed clouds were identified and their physical properties were examined in detail. Read More

2005Apr

We present a systematic numerical study of the effect of turbulent velocity fluctuations on the thermal pressure distribution in thermally bistable flows. The simulations employ a random turbulent driving generated in Fourier space rather than star-like heating. The turbulent fluctuations are characterized by their rms Mach number M and the energy injection wavenumber, k_for. Read More

2004Oct
Affiliations: 1American Museum of Natural History, New York, 2Notre Dame University, 3Notre Dame University, 4American Museum of Natural History, New York
Category: Astrophysics

Observations have suggested substantial departures from pressure equilibrium in the interstellar medium (ISM) in the plane of the Galaxy, even on scales under 50 pc. Nevertheless, multi-phase models of the ISM assume at least locally isobaric gas. The pressure then determines the density reached by gas cooling to stable thermal equilibrium. Read More

2004Sep
Affiliations: 1CRyA-UNAM, 2Korea Astronomy Observatory, 3Ferdowsi University, 4CRyA-UNAM
Category: Astrophysics

We discuss the lifetimes and evolution of clumps and cores formed as turbulent density fluctuations in nearly isothermal molecular clouds. In the non-magnetic case, clumps are unlikely to reach a hydrostatic state, and instead are expected to either proceed directly to collapse, or else ``rebound'' towards the mean pressure and density of the parent cloud. Rebounding clumps are delayed in their re-expansion by their self-gravity. Read More

In recent years, several different strategies have emerged for evolving the magnetic field in numerical MHD. Some of these methods can be classified as divergence-cleaning schemes, where one evolves the magnetic field components just like any other variable in a higher order Godunov scheme. The fact that the magnetic field is divergence-free is imposed post-facto via a divergence-cleaning step. Read More

2003May
Affiliations: 1Chungnam National University, Korea, 2Chungnam National University, Korea, 3Korea Astronomy Observatory, Korea, 4University of Minnesota, 5University of Notre Dame
Category: Astrophysics

We have studied forced turbulence of compressible magnetohydrodynamic (MHD) flows through two-dimensional simulations with different numerical resolutions. First, hydrodynamic turbulence with Mach number $_{\rm init} \equiv < v >_{\rm rms}/ c_s = 1$ and density compression ${< \delta\rho / \rho >}_{\rm rms} \simeq 0.45$ was generated by enforcing a random force. Read More

2003Jan
Affiliations: 1Chungnam National University, Korea, 2Korea Astronomy Observatory, Korea, 3Seoul National University, Korea, 4University of Minnesota, USA
Category: Astrophysics

The Parker instability, which has been considered as a process governing the structure of the interstellar medium, is induced by the buoyancy of magnetic field and cosmic rays. In previous studies, while the magnetic field has been fully incorporated in the context of isothermal magnetohydrodynamics, cosmic rays have been normally treated with the simplifying assumption of infinite diffusion along magnetic field lines but no diffusion across them. The cosmic ray diffusion is, however, finite. Read More

Here we present three-dimensional MHD models for the Parker instability in a thick magnetized disk, including the presence of a spiral arm. The $B$-field is assumed parallel to the arm, and the model results are applied to the optical segment of the Carina-Sagittarius arm. The characteristic features of the undular and interchange modes are clearly apparent in the simulations. Read More

2001Sep
Affiliations: 1Korea Astronomy Observatory, Korea, 2Chungnam National University, Korea
Category: Astrophysics

The Parker instability is considered to play important roles in the evolution of the interstellar medium. Most studies on the development of the instability so far have been based on an initial equilibrium system with a uniform magnetic field. However, the Galactic magnetic field possesses a random component in addition to the mean uniform component, with comparable strength of the two components. Read More

2001Jun
Affiliations: 1American Museum of Natural History, 2National Center for Supercomputing Applications, 3American Museum of Natural History, 4National Center for Supercomputing Applications
Category: Astrophysics

Observations have suggested substantial departures from pressure equilibrium in the interstellar medium (ISM) in the plane of the Galaxy, even on scales under 50 pc. Nevertheless, multi-phase models of the ISM assume at least locally isobaric gas. The pressure then determines the density reached by gas cooling to stable thermal equilibrium. Read More

2001Apr
Affiliations: 1Korea Astronomy Observatory, Korea, 2Chungnam National University, Korea, 3University of Minnesota, USA
Category: Astrophysics

We investigate the effects of rotation on the evolution of the Parker instability in an exponentially-stratified and uniformly-rotating magnetized gas disk by carrying out three-dimensional numerical simulations with an isothermal magnetohydrodynamic code. The instability has been initialized by random velocity perturbations. In the linear stage, the evolution is not much different from that without rotation and the mixed (undular + interchange) mode regulates the system. Read More

2000Jul
Affiliations: 1Computo Aplicado-DGSCA, UNAM, 2Korea Astronomy Observatory, 3Instituto de Astronomia, UNAM, 4Instituto de Astronomia, UNAM, 5Seoul National University, Korea, 6Chungnam National University, Korea
Category: Astrophysics

We present 2D, ideal-MHD numerical simulations of the Parker instability in a multi-component warm disk model. The calculations were done using two numerical codes with different algorithms, TVD and ZEUS-3D. The outcome of the numerical experiments performed with both codes is very similar, and confirms the results of the linear analysis for the undular mode derived by Kim et al. Read More