• 천문학논총
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• 제15권spc2호
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• pp.21-25
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• 2000

The ionosphere, the atmosphere of the earth ionized by solar radiations, has been strongly varied with solar activity. The ionosphere varies with the solar cycle, the seasons, the latitudes and during any given day. Radio wave propagation through or in the ionosphere is affected by ionospheric condition so that one needs to consider its effects on operating communication systems normally. For examples, sporadic E may form at any time. It occurs at altitudes between 90 to 140 km (in the E region), and may be spread over a large area or be confined to a small region. Sometimes the sporadic E layer works as a mirror so that the communication signal does not reach the receiver. And radiation from the Sun during large solar flares causes increased ionization in the D region which results in greater absorption of HF radio waves. This phenomenon is called short wave fade-outs. If the flare is large enough, the whole of the HF spectrum can be rendered unusable for a period of time. Due to events on the Sun, sometimes the Earth's magnetic field becomes disturbed. The geomagnetic field and the ionosphere are linked in complex ways and a disturbance in the geomagnetic field can often cause a disturbance in the F region of the ionosphere. An enhancement will not usually concern the HF communicator, but the depression may cause frequencies normally used for communication to be too high with the result that the wave penetrates the ionosphere. Ionospheric storms can occur throughout the solar cycle and are related to coronal mass ejections (CMEs) and coronal holes on the Sun. Except the above mentioned phenomena, there are a lot of things to affect the radio communication. Nowadays, radio technique for probing the terrestrial ionosphere has a tendency to use satellite system such as GPS. To get more accurate information about the variation of the ionospheric electron density, a TEC measurement system is necessary so RRL will operate the system in the near future.

• Journal of Astronomy and Space Sciences
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• 제21권4호
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• pp.315-328
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• 2004

본 연구에서는 2003년 10월과 11월에 발생한 강력한 태양활동과 우주환경의 변화에 대한 국내외 관측결과를 분석하였다. 이러한 태양활동은 거대한 흑점군, X급 이상의 강력한 플레어, 연이은 코로나물질 방출(Coronal Mass Ejections: CMEs) 및 프로톤 현상 등으로 특징지어 질 수 있다. 특히 이때 발생한 고속의 CME들은 지구 방향으로 진행하여 매우 강력한 지자기 폭풍을 일으켰다. 미국 해양대기청 우주환경예보센터에서 제시한 우주환경기준(Space Weather Scales)에 따라 국내외 관측 자료를 분석하고 위성 및 통신에 미치는 영향을 예측하였다. 또한 같은 기간동안 우리나라에서 관측된 전리층 총전자함유량(Total Electron Contents: TEC), 오로라, 전리층의 F2 임계주파수, 그리고 아리랑 위성 1호의 궤도자료를 분석함으로서 우주환경변화가 우리나라 상층대기, 위성궤도, 무선통신 등에 미치는 영향을 조사하였다.

• 천문학회보
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• 제35권2호
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• pp.46.1-46.1
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• 2010

This work is a part of our project to establish a Website which provides a list of magnetic clouds (MCs) identified by WIND and ACE spacecraft. MCs are characterized by their magnetic fields that are well described by magnetic flux rope structures, whereas interplanetary coronal mass ejections (ICMEs) are interplanetary manifestations of coronal mass ejections (CMEs), usually identified by differences of plasma and magnetic field characteristics from those in the background solar wind. It is widely accepted that, while MCs are generally identified within ICMEs, the number of MCs are significantly lower than the number of ICMEs. In our effort to identify MCs, however, we have found that there was a big problem in identification method of MCs in previous works. Generally speaking, most of the previous surveys failed in identifying MCs which encounter the spacecraft at large distances from the MC axis, or near the surface of MC structures. In our survey, MCs are identified as the region of which magnetic fields are well described by appropriate flux rope models. Thus, we could selected over 45 MCs, in 1999 solar wind data for instance, while 33 ICMEs are listed in the Website of the ACE Science Center reported by Richardson and Cane.

• 한국어병학회지
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• 제21권1호
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• pp.13-20
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• 2008

본 연구에서는 RSIV의 수온에 따른 병원성을 규명하기 위한 연구의 일환으로 수온별로 RSIV를 인위적으로 감염시킨 돌돔의 누적폐사를 관찰하고, 다른 온도에서 사육된 돌돔의 온도 스트레스 단백질인 HSP이 관여하는지를 확인하고자, 돌돔의 HSP 유전자의 염기서열 일부를 밝혔다. 각온도별 감염실험에서 17°C와 20°C의 경우 폐사가 발생하지 않았으나, 25°C 및 27°C 수조에서는 각각 90%와 80%의 누적 폐사율을 보였다. 돌돔에서 확인된 HSP 유전자의 일부는 넙치에서 확인된 HSP70와 97%의 homology를 나타내 돌돔의 HSP70으로 판단되었다.

• 천문학회보
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• 제36권2호
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• pp.97.1-97.1
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• 2011

In this study we have examined the probability of solar proton events (SPEs) and their peak fluxes depending on flare (flux, longitude and impulsive time) and CME parameters (linear speed, longitude, and angular width). For this we used the NOAA SPE list and their associated flare data from 1976 to 2006 and CME data from 1997 to 2006. We find that about 3.5% (1.9% for M-class and 21.3% for X-class) of the flares are associated with SPEs. It is also found that this fraction strongly depends on longitude; for example, the fraction for $30W^{\circ}$ < L < $90W^{\circ}$ is about three times larger than that for $30^{\circ}E$ < L < $90^{\circ}E$. The SPE probability with long duration (${\geq}$ 0.3 hours) is about 2 (X-class flare) to 7 (M-class flare) times larger than that for flares with short duration (< 0.3 hours). In case of halo CMEs with V ${\geq}$ 1500km/s, 36.1% are associated with SPEs but in case of partial halo CME ($120^{\circ}$ ${\leq}$ AW < $360^{\circ}$) with 400 km/s ${\leq}$ V < 1000 km/s, only 0.9% are associated with SPEs. The relationships between X-ray flare peak flux and SPE peak flux are strongly dependent on longitude and impulsive time. The relationships between CME speed and SPE peak flux depend on longitude as well as direction parameter. From this study, we suggest a new SPE forecast method with three-steps: (1) SPE occurrence probability prediction according to the probability tables depending on flare and CME parameters, (2) SPE flux prediction from the relationship between SPE flux and flare (or CME) parameters, and (3) SPE peak time.

• 천문학회보
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• 제38권1호
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• pp.63.1-63.1
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• 2013

To improve the forecast capability of geomagnetic storms, we consider the real time solar and near Earth conditions together, since the characteristics of CMEs can be modified during their transit from the Sun to the Earth, and the geomagnetic storms may be directly affected by not only solar events but also near Earth interplanetary conditions. Using 55 CME-Dst pairs associated with M- and X-class solar flares, which have clearly identifiable source regions during 1997 to 2003, we confirm that the peak values of negative magnetic field Bz and duskward electric field Ey prior to Dst minimum are strongly related with Dst index. We suggest the solar wind criteria (Bz<-5 nT or Ey>3 mV/m for t>2 hr) for moderate storm less than -50 nT by modifying the criteria for intense storms less than -100 nT proposed by Gonzalez and Tsurutani (GT, 1987). As the results, 90% (28/31) of the storms are correctly forecasted by our criteria. For 15 exceptional events that are incorrectly forecasted by only CME parameters, 12 cases (80%) can be properly forecasted by solar wind criteria. When we applying CME and solar wind conditions together, all geomagnetic storms (Dst<-50 nT) are correctly forecasted. Our results show that, the storm forecast capability of the 2~3 days advanced warning based on CME parameters can be improved by combining with the urgent warning based on the near Earth solar wind condition.

• 천문학회보
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• 제36권1호
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• pp.39.2-39.2
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• 2011

In this study we have examined the occurrence probability of solar proton events (SEPs) and their peak fluxes depending two CME parameters, linear speed and angular width. For this we used the NOAA SPE events and their associated CME data from 1997 to 2006. As a result, the probability strongly depends on two parameters as follows. In the case of halo CME whose speed is equal to and faster than 1500km/s, 36.1% are associated with SPEs but in the case of partial halo CME ($120^{\circ}{\leq}AW$ < $359^{\circ}$) whose speed is $400{\leq}V$ < $1000km/s$, only 0.9% are associated with SPEs. When we consider only front-side CMEs, 45.3% are associated with SPEs in the first case and 1.8% are associated with them in the second case. Both of whole CME data group and front-side CME data group have similar tendencies. The probabilities are different as much as 4.9 to 23 times according to the CME speed and 1.6 to 6.5 times to the angular width. We have also examined the relationship between CME speed and proton peak flux as well as its dependence on angular width (partial halo CME and halo CME), longitude (east, center, and west) and direction parameter (< 0.4 and {\geq} 0.4). Our results show that the relationships strongly depend on longitude as well as direction parameter. In addition, the relationship using the radial CME speed based on a cone model has a higher correlation coefficient than that using the projected CME speed.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.38.3-39
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• 2010

While major solar proton events (SPEs) come from the coronal mass eject (CME)-driven shocks in solar wind, there are many evidences that potentiality of CMEs to generate SPEs depends on its early evolution near the Sun and on different solar activities observed around the CME liftoff time. To decipher origin of SPE release, we have investigated onset time comparison of the SPE with CME, metric type II radio burst, and hard X-ray flare. For this, we select 30 SPEs observed from 1997 to 2006 by using the particle instrument ERNE onboard SOHO, which allows proton flux anisotropy measurement in the energy range ~10 - 50MeV. Onset time of the SPEs is inferred by considering the energy-dependent proton transport time. As results, we found that (1) SPE onset time is comparable to that of type II but later than type III onset time and HXR start time, (2) SPE onset time is mostly later than the peak time of HXR flare, (3) almost half of the SPE onsets occurred after the HXR emission, and (4) there are two groups of CME height at the onset time of SPE; one is the height below 5 Rs (low corona) and the other is above 5Rs (high corona). In this talk, we will present the onset time comparison and discuss about the origin of the SPE onset.

• Journal of Astronomy and Space Sciences
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• 제33권4호
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• pp.279-285
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• 2016

The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

• 사회복지연구
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• 제48권3호
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• pp.145-169
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• 2017

신 사회위험의 하나의 축은 가족 구조의 재편과 여성의 경제활동참여율 증가에 따라 발생한 새로운 욕구들이다. 일가정양립정책이 여성 경제활동에 미치는 영향에 대한 연구는 활발하게 이루어지고 있음에도 불구하고, 여성 취업에 영향을 미칠 수 있는 제도로서 생산레짐의 함의를 살펴보는 연구는 미진한 실정이다. 본 연구는 룩셈부르크 소득연구(Luxembourg Income Study) 자료를 이용하여 생산레짐과 일가정양립정책이 성별 임금격차에 미치는 영향을 분석하였다. 분석결과, 기업특정적 기술 활용이 활발한 조정경제시장에서 여성의 임금이 남성에 비해 통계적으로 유의하게 낮게 나타나 성별 임금격차가 증가하는 것으로 나타났다. 반면, 육아휴직과 보육지출은 여성의 임금순위를 향상시키는 것으로 나타나 성별 임금순위격차를 약화시키는 것으로 분석되었다. 본 연구는 제도적 측면에서 생산레짐과 일가정양립정책이 여성의 임금순위에 미치는 영향을 실증적으로 평가했다는 데 그 의의가 있다.