애초에 하늘을 날던 물고기_강혜성/한국문연

강혜성 시와세계 2023 시와세계 Vol.- No.82

Ecosystemic Resilience Relative to an Increasing Population of Unwed Mothers in Korea

강혜성,Sandra A. Rigazio-DiGilio 한국건강심리학회 2023 한국심리학회지 건강 Vol.28 No.2

Despite positive changes in the cultural notion of unwed mothers in Korea, they still experience numerous challenges in their child-rearing efforts. In this research, we explored unwed mothers’ experiences and perceptions about their own resilience in wider contexts and the facilitative factors that may contribute to it through interviews and community genograms. Participants included 18 unwed mothers raising one or more children with the youngest child aged 0–6 years. Results revealed six themes in which these mothers drew on their resources to overcome challenges when navigating new social contexts as unwed mothers. Based on these findings, we proposed the Korean Unwed Mothers’ Ecosystemic Resilience model to conceptualize resilience and its facilitative factors. Implications on social programs and policies, as well as implications for the training of and support for counselors and health professionals, are discussed.

Re-Acceleration of Fossil Electrons by Shocks Encountering Hot Bubbles in the Outskirts of Galaxy Clusters

강혜성 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.6

Galaxy clusters are known to host many active galaxies (AGNs) with radio jets, which could expand to form radio bubbles with relativistic electrons in the intracluster medium (ICM). It has been suggested that fossil relativistic electrons contained in remnant bubbles from extinct radio galaxies can be re-accelerated to radio-emitting energies by merger-driven shocks via diffusive shock acceleration (DSA), leading to the birth of radio relics detected in clusters. In this study we assume that such bubble consist primarily of thermal gas entrained from the surrounding medium and dynamically-insignificant amounts of relativistic electrons. We also consider several realistic models for magnetic fields in the cluster outskirts, including the ICM field that scales with the gas density as $B_{\rm ICM}\propto n_{\rm ICM}^{0.5}$. Then we perform time-dependent DSA simulations of a spherical shock that runs into a lower-density but higher-temperature bubble with the ratio $n_{\rm b}/n_{\rm ICM} \approx T_{\rm ICM}/T_{\rm b}\approx 0.5$. We find that inside the bubble the shock speed increases by about 20 \%, but the Mach number decreases by about 15\% in the case under consideration. In this re-acceleration model, the observed properties of a radio relic such as radio flux, spectral index, and integrated spectrum would be governed mainly by the presence of seed relativistic electrons and the magnetic field profile as well as shock dynamics. Thus it is crucial to understand how fossil electrons are deposited by AGNs in the ICM and how the downstream magnetic field evolves behind the shock in detailed modeling of radio relics.

NONTHERMAL RADIATION FROM RELATIVISTIC ELECTRONS ACCELERATED AT SPHERICALLY EXPANDING SHOCKS

강혜성 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.1

We study the evolution of the energy spectrum of cosmic-ray electrons accelerated at sphericallyexpanding shocks with low Mach numbers and the ensuing spectral signatures imprinted in radiosynchrotron emission. Time-dependent simulations of diffusive shock acceleration (DSA) of electrons inthe test-particle limit have been performed for spherical shocks with parameters relevant for typical shocksin the intracluster medium. The electron and radiation spectra at the shock location can be describedproperly by the test-particle DSA predictions with instantaneous shock parameters. However, the volumeintegrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws,because the shock compression ratio and the flux of injected electrons at the shock gradually decrease asthe shock slows down in time. So one needs to be cautious about interpreting observed radio spectra ofevolving shocks based on simple DSA models in the test-particle regime.

RADIO EMISSION FROM WEAK SPHERICAL SHOCKS IN THE OUTSKIRTS OF GALAXY CLUSTERS

강혜성 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.2

In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with $\rho\propto r^{-n}$ in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volume-integrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about $0.7$ or $7\muG$, at the shock age of $\sim 50$~Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from $\alpha_{\rm inj}$ to $\alpha_{\rm inj}+0.5$ over 0.1--10~GHz, where $\alpha_{\rm inj}$ is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around $1$~GHz.

DIFFUSIVE SHOCK ACCELERATION BY MULTIPLE WEAK SHOCKS

강혜성 한국천문학회 2021 Journal of The Korean Astronomical Society Vol.54 No.3

The intracluster medium (ICM) is expected to experience on average about three passages of weak shocks with low sonic Mach numbers, M≤3, during the formation of galaxy clusters. Both protons and electrons could be accelerated to become high energy cosmic rays (CRs) at such ICM shocks via diffusive shock acceleration (DSA). We examine the effects of DSA by multiple shocks on the spectrum of accelerated CRs by including in situ injection/acceleration at each shock, followed by repeated re-acceleration at successive shocks in the test-particle regime. For simplicity, the accelerated particles are assumed to undergo adiabatic decompression without energy loss and escape from the system, before they encounter subsequent shocks. We show that in general the CR spectrum is flattened by multiple shock passages, compared to a single episode of DSA, and that the acceleration efficiency increases with successive shock passages. However, the decompression due to the expansion of shocks into the cluster outskirts may reduce the amplification and flattening of the CR spectrum by multiple shock passages. The final CR spectrum behind the last shock is determined by the accumulated effects of repeated re-acceleration by all previous shocks, but it is relatively insensitive to the ordering of the shock Mach numbers. Thus multiple passages of shocks may cause the slope of the CR spectrum to deviate from the canonical DSA power-law slope of the current shock.

RE-ACCELERATION MODEL FOR THE “TOOTHBRUSH” RADIO RELIC

강혜성 한국천문학회 2016 Journal of The Korean Astronomical Society Vol.49 No.3

The Toothbrush radio relic associated with the merging cluster 1RXS J060303.3 is presumed to be produced by relativistic electrons accelerated at merger-driven shocks. Since the shock Mach number inferred from the observed radio spectral index, $M_{\rm radio}\approx 2.8$, is larger than that estimated from X-ray observations, $M_{\rm X}\lesssim 1.5$, we consider the re-acceleration model in which a weak shock of $M_s\approx 1.2-1.5$ sweeps through the intracluster plasma with a preshock population of relativistic electrons. We find the models with a power-law momentum spectrum with the slope, $s\approx 4.6$, and the cutoff Lorentz factor, $\gamma_{e,c}\approx 7-8\times 10^4$ can reproduce reasonably well the observed profiles of radio fluxes and integrated radio spectrum of the head portion of the Toothbrush relic. This study confirms the strong connection between the ubiquitous presence of fossil relativistic plasma originated from AGNs and the shock-acceleration model of radio relics in the intracluster medium.

SHOCK ACCELERATION MODEL WITH POSTSHOCK TURBULENCE FOR GIANT RADIO RELICS

강혜성 한국천문학회 2017 Journal of The Korean Astronomical Society Vol.50 No.4

We explore the shock acceleration model for giant radio relics, in which relativistic electrons are accelerated via diffusive shock acceleration (DSA) by merger-driven shocks in the outskirts of galaxy clusters. In addition to DSA, turbulent acceleration by compressive MHD modes downstream of the shock are included as well as energy losses of postshock electrons due to Coulomb scattering, synchrotron emission, and inverse Compton scattering off the cosmic background radiation. Considering that only a small fraction of merging clusters host radio relics, we favor a reacceleration scenario in which radio relics are generated preferentially by shocks encountering the regions containing low-energy ($\gamma_{\rm e} \lesssim 300$) cosmic ray electrons (CRe). We perform time-dependent DSA simulations of spherically expanding shocks with physical parameters relevant for the Sausage radio relic, and calculate the radio synchrotron emission from the accelerated CRe. We find that significant level of postshock turbulent acceleration is required in order to reproduce broad profiles of the observed radio flux densities of the Sausage relic. Moreover, the spectral curvature in the observed integrated radio spectrum can be explained, if the putative shock should have swept up and exited out of the preshock region of fossil CRe about 10~Myr ago.

우주배경복사를 통하여 본 우주의 역사

강혜성 자연사 미래환경학회(구 자연사환경학회) 2003 자연사 미래환경학회 학술발표논문집 Vol.2003 No.-

아동기 역경 경험과 아동의 미디어기기 중독과의 연관성

강혜성,기쁘다 한국건강심리학회 2023 한국심리학회지 건강 Vol.28 No.5

본 연구는 아동기 역경 경험(Adverse Childhood Experiences [ACEs])이 아동의 미디어기기 중독에 미치는 영향력을 검증하고자 하였다. 이를 위해 한국육아정책연구소의 한국아동패널 2008년(1차)부터 2020년(13차) 종단 자료를 활용하여 아동이 생애 초기부터 경험한 다양한 역경 경험(가정폭력 노출, 신체적 학대, 정서적 학대, 또래폭력 피해, 부모의 사망·이혼·별거)이 초등학교 6학년(13차) 때의 미디어기기 중독에 미치는 영향력을 로지스틱 분석을 통해 분석하였으며, 그 연관성이 성별에 따라 어떻게 달라지는지 검토하였다. 분석 결과 아동기 역경 경험이 많을수록 미디어기기 중독을 보일 승산이 높았으며, 정서적 학대, 신체적 학대, 또래폭력 피해가 미디어기기 중독에 영향을 미치는 것으로 나타났다. 성별에 따라 나누었을 때 연구결과는 상이하게 나타났는데, 남아의 경우 신체적 학대와 정서적 학대가 미디어기기 중독에 유의한 영향을 미친 반면, 여아의 경우 정서적 학대만 미디어기기 중독에 유의미한 영향을 미쳤다. 아동기 역경 경험의 누적효과의 경우 남아와 여아 모두 누적 역경 경험이 많을수록 미디어기기 중독을 보일 확률이 높았으며, 여아의 경우 승산비가 더 큰 것으로 나타났다. 이를 토대로 미디어기기 중독 이해 및 예방을 위한 실천적, 정책적 방안들을 논의하였고, 향후 연구 과제를 제안하였다. This study investigated the influence of adverse childhood experiences (ACEs) on media device addiction using longitudinal data from the Panel Study of Korean Children (PSKC), from waves 1 to 13. The ACEs predictor variables included family violence, physical abuse, emotional abuse, experiences of being bullied, parents’ death, divorce, and separation. Frequency and logistic regression analyses were conducted. The results showed that the cumulative ACEs indicated a higher odds ratio on media device addiction. Physical abuse, emotional abuse, and experiences of being bullied were statistically significant predictors of media device addiction. The factors influencing media device addiction were different by gender. Men had a higher risk of media device addiction when they experienced physical abuse or emotional abuse. For women, only emotional abuse increased the likelihood of media device addiction. The influence of ACEs on media device addiction was discussed with an emphasis on prevention and intervention strategies.