Satellite observations in the solar wind (1 au, closer to the Sun (~0.3 au) and farther (~5 au)) indicate persistent existence of well-organized small-scale transient magnetic structure in a form of twisted magnetic field lines and nested flux surfaces often referred to as flux rope. This is similar to but distinguished from typical (much larger scale) magnetic clouds in the sense that the spatial or temporal scale is much smaller or shorter and its occurrence rate is far higher. Its intrinsic nature in various aspects is currently a subject of intense research. In particular, unlike the normal magnetic clouds which are ejected from the solar corona, the origin of the small-scale flux ropes has not yet been unambiguously identified. Suggestions exist that they come from small solar eruptions (ejections) or are created by magnetic reconnection in the heliospheric current sheet or turbulence in the solar wind. Frequent occurrence of this well-organized magnetic structure is a promising feature for promoting space weather prediction capability. In this talk, I will review the current understanding and major issues of this intriguing small transient flux ropes identified from various satellite observations.

Giant molecular clouds (GMCs) are the primary sites of star formation and stellar feedback in galaxies. UV radiation emitted by newborn massive stars is believed to play a key role in destroying GMCs and limiting star formation efficiency (SFE) therein, but the details of how remain elusive. In this talk, I will report on recent progress we made in modeling of star-forming GMCs with UV radiation feedback. I will overview observational constraints on the GMC lifecycle and present results of radiation (M)HD simulations, focusing on the effects of turbulence and magnetic fields. I will also briefly discuss (1) the escape of ionizing radiation and implications for diffuse ionized gas; and (2) why it is difficult to observationally validate the anti-correlation between turbulence level and star formation rate predicted by theory. I will end by talking about ongoing efforts in modeling GMC destruction with all major forms of massive star feedback (UV radiation, winds, and supernovae).

- 우리나라의 생물자원 소개(약초와 독초, 식용버섯과 독버섯, 식용곤충 등 특허)

- 우리 땅에 피는 귀한 야생화

- 건강생활과 먹거리(산나물, 야생식용버섯, 신작물 등)

- 귀촌하면 키워보고 싶은 약초 100가지 등

- 세상 변화의 원천은 자연(생체모방기술)

- 미래는 생물자원 전쟁(나고야의정서) 등

Cosmic ray flux is an important factor to response to solar activity. Its profile shows the decreasing shape by interaction of enhanced interplanetary magnetic field structure. When the solar eruptions such as solar proton events by flares arrive at the Earth, the profile of cosmic ray flux changes to sharp increasing shape at the ground neutron monitor. The former is well known as “Forbush decrease”, while the latter is known as “Ground level enhancement”. Cosmic ray working group began neutron monitor research in the early 2000s. At first, our group focused on the interaction between solar wind/interplanetary magnetic field and cosmic ray particles. The main topics are simultaneity of Forbush decreases, anisotropy of diurnal variation, relationship between solar proton events and ground level enhancements and so on. The first of neutron monitor by our group has installed at Daejeon in October, 2011. Another neutron monitor has been installed at Jang Bogo in Antarctica in December, 2015. The observational data by both neutron monitors have registered at Neutron Monitor Database (NMDB, http://www01.nmdb.eu/data/) on April, 2018. I introduce the brief installation of neutron monitor at Jang Bogo and the scientific achievements in cosmic ray research.

Astronomy and paleontology have many things in common. In childhood, anyone is interested in the stars in the sky and can memorize the names of numerous dinosaurs. Dinosaurs 100 million years ago are buried Gobi Desert in Mongolia, which is good for stargazing because there is little rain or clouds. It is also common that amateur researchers, not professional researchers, can contribute to research field. Just as amateur astronomers discover new comet-like objects, amateur fossil hunters and even curious travelers can find dinosaurs. Most powerful hypotheses about the extinction of dinosaurs is a collaboration between astronomy and paleontology. Unlike astronomical studies about cosmic ‘space’, how are fossils that are the research subject of cosmic and earth ‘time’ studies made, how are they discovered, and how are they studied?

Alfvén waves are considered to be physically important in understanding  physical processes in the solar corona such as nonthermal heating, solar wind acceleration and  the abundance enhancement of low first-ionization-potential elements.  However, it is still not clear how these waves are excited in the lower atmosphere. To reveal their physical origin,  we  have attempted to detect Alfvénic waves in the solar chromosphere using the spectroscopic method. By analyzing  the spectral data taken by the Fast Imaging Solar Spectrograph of the 1.6 meter Goode Solar Telescope, we successfully detected the Alfvénic waves in the  superpenumbral fibrils around a sunspot. This is the first spectroscopic detection of Alfvénic waves in the solar chromosphere. These waves are found to be physically associated with the three-minute umbral oscillation.  We conclude that the Alfvénic waves excited by the slow-to-Alfvén mode conversion may prevail in the solar chromosphere. 

An antenna and a receiver are needed to effectively receive microwave signals from the universe.
For such a receiver design, the experimental purpose and antenna characteristics should be considered.
In recent radio astronomy research, there is a demand for wideband multi-channel simultaneous observation of the receiver, and the design of a Compact Tripple Band Receiver is in progress.
In addition, this talk will introduce the design of a receiver for observation of CMB(Cosmic Microwave Background).
The receiver for CMB observation is very different from the conventional radio telescope receiver, and the design considerations are also different.
Finally, these receivers require cryogenic cooling during operation.
Various technologies and design methods for cryogenic cooling of receivers will be introduced.

Cosmology is a study to understand the origin, fundamental property, and evolution of the universe. Nowadays, many observational data of galaxies have become available, and one needs large-volume numerical simulations with good quality of the spatial distribution for a fair comparison with observation data. On the other hand, since galaxies' evolution is affected by both gravitational and baryonic effects, it is nontrivial to populate galaxies only by N-body simulations. However, full hydrodynamic simulations with large volume are computationally costly. Several attempts have been proposed to overcome such difficulties, such as applying alternative galaxy assignment methods or painting baryonic feature learned from hydrodynamic simulations to N-body simulations.
In this talk, I would like to introduce the MBP-galaxy abundance matching and mock galaxy catalogs of the Horizon Run 4 and Multiverse simulations, large-volume cosmological N-body simulations done by the Korean community. Also, I would like to briefly discuss how recent deep-learning techniques could help cosmological studies. 

The advent of far-infrared/submillimeter observational facilities showed that a significant fraction of star formation is placed in heavily dust-attenuated galaxies in the early Universe. Due to the nature of galaxy spectral energy distribution and the effect of K-correction, galaxies selected at submillimeter wavelengths are likely to be vigorous star-forming high-redshift galaxies. Based on their characteristics – gas-rich, large stellar mass, frequent contribution from the active galactic nuclei – they are spotlighted to show the early stage of massive galaxy evolution. In this talk, I will introduce several ongoing submillimeter extragalactic surveys, particularly focusing on the JCMT/SCUBA-2 survey on the North Ecliptic Pole region.

The lives of galaxies and their supermassive black holes (SMBH) are probably intimately linked. Although mergers are considered a promising triggering mechanism for AGN activity, numerous studies have shown that AGN hosts are no more likely to appear morphologically disturbed than inactive galaxies. To study the AGN-Merger connection, i.e., merger activity in AGNs and AGN activity in merging systems, we run a suite of high resolution zoom-in cosmological hydrodynamic simulations. These simulations are post-processed with a radiative transfer code to generate HST mock observations of redshift 0.5

Alfven waves are ubiquitous in space and laboratory plasma. As Hannes Alfven himself described them as electromagnetic-hydromagnetic waves in 1942, magnetohydrodynamic (MHD) approach is often useful in understanding Alfven waves. However, it is also found that energetic particles rather than hydrodynamic motion are responsible for generation of certain types of Alfven waves called poloidal modes in the magnetosphere through wave-particle interaction and/or kinetic instabilities. One of most important and long-standing questions in Alfven waves can be how these poloidal Alfven waves are often observed for a long time even at the absence of corresponding driving sources, but no theories have been available yet. Recently, we have developed a theory on the existence of long-lasting poloidal Alfven waves, which will successfully illustrate how the energetic particles excite Alfven waves and then keep them persist in space. We also present a statistical database to compare its events with our theoretical conditions, which are very consistent with the observations.

Today’s cosmology requires precision and accuracy of distance measurements more than ever. The tip of the red giant branch (TRGB) is an ideal standard candle for the cosmology of the nearby universe. The TRGB will be more popular in the coming age with future telescopes. Some interesting science cases in the TRGB cosmology will be presented: 1) the Hubble tension, 2) Virgo infall and dark matter, 3) almost dark galaxies, and 4) dark matter-free galaxies.

Baryonic feedback refers to the modification of the matter distribution due to baryonic processes such as stellar winds, AGN jets, etc. The effect is a nuisance to weak lensers, who proclaim to accurately constrain cosmological parameters by measuring the universe's power spectrum. In this talk, after providing a review of the community's effort to address the systematics through various approaches, I will present our measurement of baryonic feedback, which is the first detection purely based on cosmological lensing surveys. The study illustrates tremendous future opportunities available in the era of the Stage IV weak lensing surveys enabling precision cosmology but also improving our understanding of sub-grid astrophysics.

An exciting discovery made by space- and ground-based high-energy missions is the detection of gamma-rays from over 3,000 Active Galactic Nuclei. Despite their intensive study, the location and origin of gamma-rays remains a mystery. The question of what powers gamma-ray flares is ultimately related to the energy dissipation and particle acceleration processes at work in relativistic jets, which is still an open question. In this talk, I will (1) present some exciting results of our recent study using multi-frequency and multi-messenger observations, (2) discuss the scientific potential of gamma-ray polarimetry, and (3) explore the scientific opportunities and wealth of information expected from the synergy of multi-wavelength polarimetry that will be brought to multi-messenger astronomy.

Turbulent flow in the convective envelope generates resonant sound waves trapped in the stellar interiors and observed as non-radial oscillations of the Sun and Sun-like stars. Investigating the observed mode frequencies of the oscillations allows us to improve our knowledge on the internal structure and dynamics of the Sun and Sun-like stars. In this contribution comprising two parts, I summarize basics of helioseismology and discuss effects of stellar magnetic activity on the global seismic parameters. We report statistical behaviors of the global seismic parameters and their implications found in recent analysis we carried out recently. We briefly conclude by discussing issues not to be mentioned here.

Astrophysical sources of very-high-energy (VHE) gamma-ray radiation provide unique information about astrophysical particle acceleration

and cosmic-ray production. In particular, compact binary systems, composed of a compact object (a neutron star or black hole) in orbit

with a massive stellar companion, provide an ideal environment for VHE gamma-ray production.

They are not only powerful particle accelerators, but they also exhibit periodic emission that makes them excellent astrophysical laboratories.

However, only a handful of binary systems have ever been observed in VHE gamma rays.

Partly, this is because VHE gamma-ray binaries appear to be very rare, and part is due to observational bias.

Most instruments operating at TeV are pointed and must allocate time to observing many kinds of objects.

The High Altitude Water Cherenkov (HAWC) Observatory, on the other hand, has high uptime (duty cycle >95%)

and a wide field of view (2 sr), making it well-suited for observing transient and time-varying sources such as binaries.

HAWC is also currently the only detector that is sensitive to gamma-ray photons above 10 TeV. SS 433 is a known microquasar

that has two jets ("east" and "west") terminating in radio lobes of a surrounding supernova remnant, W 50.

The recent observation of SS 433 with HAWC marked the first direct evidence of gamma-ray emission from the jets of a microquasar.

Using HAWC data, we have measured a VHE flux of e1 in the east lobe and w1 in the west lobe with a combined

post-trial statistical significance of 5.4 sigma.

From the International Year of Astronomy in 2009 - The Universe Yours to Discover; to IAU 100 Years Celebrations in 2019 - Under One Sky,

the IAU Office for Astronomy Outreach (IAU OAO) the IAU engages the public in astronomy through access to astronomical information

and communication of the science of astronomy.

The IAU Office for Astronomy Outreach work focuses on building bridges between the IAU and the global astronomy community

of outreach professionals, educators, amateur and professional astronomers, and the public.

Through international cooperation, we envision to make astronomy a science that is accessible to all.

Hydrogen- and helium-ionizing photons from stars and quasars can propagate through the intergalactic medium (IGM)

and change the chemical and kinematical properties of IGM through ionization and heating.

This process, the cosmic reionization, is believed to have started with the birth of first stars and ended

when all the gas in the IGM got ionized due to the plethora of ionizing photons.

Continuous percolation of individual H II regions generate H II regions in cosmological scales,

and this enables us to probe the process itself and the collective properties of radiation sources

through observations targeting large-scale phenomena.

We review our own reionization models that include first stars at high redshift, z~30-15, 

and show the current constraint on such models made by the Planck (cosmic microwave background: CMB)

and EDGES (Experiment to Detect the Global EoR Signature, on 21-cm).

We also present how improved CMB and 21-cm observations, e.g. LiteBIRD (Lite (Light) satellite for the studies of B-mode polarization

and Inflation from cosmic background Radiation Detection) and SKA (Square Kilometre Array), can further tighten the constraint

on reionization models.

Molecular clouds form out of the surrounding diffuse gas through the conversion of atomic (HI)

to molecular hydrogen (H2), and previous Galactic and extragalactic observations have suggested

that this HI-to-H2 transition is a major bottleneck process toward star formation.
Among two main flavors of HI, the cold and warm neutral medium (CNM and WNM),

the cold component is expected to play a critical role.

For example, the CNM is far more effective at forming and shielding H2 thanks to its higher density.

In addition, numerical simulations have found that CNM structures have physical properties that resemble those
of molecular clouds, implying that the initial conditions for star formation are set before the gas becomes molecular.

Despite its vital importance for the HI-to-H2 transition and ensuing star formation,
however, the CNM in and around molecular clouds remains largely unexplored.

In this talk, I will describe my attempts for the last few years to understand the roles of the CNM in the formation

and evolution of molecular clouds and present some preliminary results from these attempts.

태양계는 46억년의 긴 나이를 가지고 있다. 따라서 현재의 태양계가 수억년 이상 별 변화없이 비슷한 상태를 유지하고 있으리라,

태양계의 천체들도 수십억년 전에 형성되었으리라 생각하기 쉽다.

적어도 태양계의 행성간 공간에 퍼져 있는 티끌의 경우에 이는 확실하게 사실이 아니다.

행성간 티끌은 보통 짧으면 수년, 길어도 수십만년 정도밖에는 태양계에 머무르지 못한다.

그럼에도 태양계에는 현재 행성간 티끌이 풍부하게 존재한다. 이는 결국 태양계의 다양한 천체에서 끊임없이 티끌이 공급되고 있다는 뜻이 된다.

그간의 연구로 티끌을 공급하는 천체도, 티끌이 방출되는 기작도 매우 다양함이 알려졌다.

바꾸어 말하면 행성간 티끌의 연구를 통하여 특정 천체의 활동성(티끌 방출)을 설명하기 위해 제시된 모형이 얼마나 현실적인지,

그렇다면 그 현상은 얼마나 흔한지, 비슷한 천체가 태양계에는 얼마나 어떻게 분포할지를 모두 살펴볼 수 있다.
본 강연에서는 행성간 티끌을 매개로 소행성, 혜성, 해왕성 바깥 천체 등 태양계 소천체의 분포와 진화,

이들이 보이는 활동성을 간략히 설명할 것이며, 행성간 티끌의 기원, 혜성 기원 티끌의 진화,

소행성에서의 티끌 방출 기작에 대한 자체 연구도 간단히 소개하려 한다.

태양은 11년 주기로 다양한 플라즈마 현상들을 보여주고 있다.

극대기의 태양은 대규모의 폭발과 물질분출 현상을 일으켜 지구주변의 환경에 급격한 변화를 초래하지만,

극소기 동안에도 작지만 끊임없는 활동으로 기후 변화 등 장기간에 걸친 지구환경변화에 영향을 준다.

최근, 우리는 다양한 파장의 지상 망원경과 우주 망원경을 통해 태양을 자세히 관측하고 좀 더 잘 이해하게 되었다.

이번 강연에서는 지난 두 차례의 태양주기 동안 수행했던 조용한 태양과 역동적인 태양에 대한 나의 다양한 연구결과들을 정리하고,

새로운 태양주기를 맞아 현재 진행하고 있는 연구를 소개하고자 한다.

우주의 물질 분포를 정확히 측정하는 것은 관측 우주론에서 중요한 요소이다.

이것은 우주 모형과 은하를 포함한 구조 형성 시나리오를 검증하는 데 중요한 도구로 활용될 수 있기 때문이다.

본 강연에서는 외부 은하 탐사를 통해 알게 된 우주 속 우리의 위치(cosmic address)를 먼저 살펴본다.

그리고, 우주의 물질 분포 측정을 위해 진행된 분광 탐사에 대해서 간략히 살펴보고,

국내에서 진행되고 있는 다천체 분광기 개발을 통한 가까운 우주 분광 탐사 계획(K-SPEC)을 소개하고자 한다.

* 특이사항: 이번 강연은 학부생 분들도 쉽게 이해할 수 있도록 준비되었습니다.

Neutral (HI) gas clouds associated with galaxies are responsible for fuelling the star-formation in the universe.

These stars further inject metals back into the neutral gas clouds both within and outside the galaxy.

The circle continues with metals, radiation and dust from stars influencing the neutral to molecular gas (HI-H2) transition

which further influence the next generation of star-formation. Further, gas abundance and kinematics are influenced

by larger factors such as galactic interactions and mergers. 
In my talk, I will focus primarily on my study of high column density neutral gas clouds (Extremely strong Damped Lyman-alpha absorbers, or ESDLAs)

that are observed as absorption signature along the line-of-sight (LOS) of a quasar.

I will further look at the HI-H2 transition and interesting results relevant to diffuse molecular gas.

I will also discuss comparisons between low and high star-forming environment and talk about different samples and techniques

that can be used to study them.

I would like to give my intellectual journey that led to the involvements in gravitational wave science.

My PhD thesis was about the dynamical evolution of dense star clusters including the effects of the binaries and stellar collisions.

The black holes are interesting objects in view of the stellar dynamics in many aspects.

The observational evidence for the supermassive black hole was growing rapidly in late 1980s as the high resolution spectroscopic observations became available,

and the advancement of the speckle interferometry toward the Galactic Center.

My research area expanded to the origin of the supermassive black holes and their interactions with surrounding stars.
In  2000, I was invited to a LISA symposium held in Golm, Germany, where I was first exposed to the gravitational wave experiments.

I felt that the gravitational wave would become an important tool for astronomy and formed a gravitational-wave study group in late 2003.

From 2004, the Korean Gravitational Wave Group (KGWG) organized summer schools every year under the sponsorship

of Asian-Pacific Center for Theoretical Physics (APCTP) and Korea Institute for Science and Technology Information (KISTI) focusing on the general relativity

and gravitational waves and educated ourselves on these topics.

In 2009, KGWG became a member of the LIGO Scientific Collaboration.

While working on the LIGO collaboration, I also continued to study the roles of the black holes in star clusters and found that the black hole merger events

could be more abundant than neutron star binary coalescence in LIGO observations.

The gravitational wave community in Korea is growing and KASI now pursues gravitational wave experiments by developing the measurement techniques
that could enhance the sensitivity significantly.

I will close my talk by giving prospects of gravitational wave astrophysics.

Comets and carbonaceous asteroids are the remnants of planetesimals that remain in the current solar system.

In recent years, the differences between these objects have become ambiguous. In this talk,

we consider the differences between these objects during the formation epoch, especially based on the polarimetric observation results.

Based on the scientific motivation, we will explain why a polarization instrument is necessary, especially in a domestic observatory.
We would invite researchers who are NOT so much interested in solar system research to participate.

In particular, we would ask those who are dissatisfied with the weather conditions in the domestic observatories,

or those interested in polarimetric observations, and think about a future polarimetric instrument in Korea together.

The physical properties of group and cluster galaxies are distinct from that of field galaxies.

Red and passive galaxies with a low star formation rate are dominant in dense environments.

Various environmental processes (e.g., tidal interaction and ram pressure stripping (RPS)) can play an important role

in changing galaxy properties (e.g., ISM and star formation) and galaxy evolution. Molecular gas is the direct fuel for star formation.

Therefore, in order to better understand a change of star formation in group and cluster galaxies,

it is essential to study how environmental processes affect the molecular gas of group and cluster galaxies.

Using high-resolution CO data (e.g., SMA and ALMA),

we find that the environmental processes can change molecular gas properties and star formation of group and cluster galaxies.

In particular, the asymmetric distribution of CO gas is found in our samples.

In this talk, I will show strong evidence that the molecular gas of Virgo spiral galaxies is disturbed by ram pressure.

I will also show preliminary results of our new CO study on group galaxies with the ALMA/ACA.