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1984년 ~ 2025년까지 1,249 건의 한국우주과학회지를 계간으로 확인하실 수 있습니다.
- The Korean Space Science Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-052x (ISSN : 1225-052x)
1225-052x
- DB구축현황 : 1,249건 (DB Construction : 1,249 Articles)
총 게시글 1,249건
페이지 23/125
221
- Cho, Kihyeon
- Journal of astronomy and space sciences
- 33, n.1
- pp.63-67
- 2016
- 원문 바로보기
The Korea Institute of Science and Technology Information (KISTI) has been studying the e-Science paradigm. With its successful application to particle physics, we consider the application of the paradigm to astroparticle physics. The Standard Model of particle physics is still not considered perfect even though the Higgs boson has recently been discovered. Astrophysical evidence shows that dark matter exists in the universe, hinting at new physics beyond the Standard Model. Therefore, there are efforts to search for dark matter candidates using direct detection, indirect detection, and collider detection. There are also efforts to build theoretical models for dark matter. Current astroparticle physics involves big investments in theories and computing along with experiments. The complexity of such an area of research is explained within the framework of the e-Science paradigm. The idea of the e-Science paradigm is to unify experiment, theory, and computing. The purpose is to study astroparticle physics anytime and anywhere. In this paper, an example of the application of the paradigm to astrophysics is presented.
222
- Chai, Yating
- Journal of astronomy and space sciences
- 33, n.2
- pp.75-92
- 2016
- 원문 바로보기
It is generally believed that the high energy emissions from isolated pulsars are emitted from relativistic electrons/positrons accelerated in outer magnetospheric accelerators (outergaps) via a curvature radiation mechanism, which has a simple exponential cut-off spectrum. However, many gamma-ray pulsars detected by the Fermi LAT (Large Area Telescope) cannot be fitted by simple exponential cut-off spectrum, and instead a sub-exponential is more appropriate. It is proposed that the realistic outergaps are non-stationary, and that the observed spectrum is a superposition of different stationary states that are controlled by the currents injected from the inner and outer boundaries. The Vela and Geminga pulsars have the largest fluxes among all targets observed, which allows us to carry out very detailed phase-resolved spectral analysis. We have divided the Vela and Geminga pulsars into 19 (the off pulse of Vela was not included) and 33 phase bins, respectively. We find that most phase resolved spectra still cannot be fitted by a simple exponential spectrum: in fact, a sub-exponential spectrum is necessary. We conclude that non-stationary states exist even down to the very fine phase bins.
223
- Jung, Jongil
- Journal of astronomy and space sciences
- 33, n.4
- pp.345-348
- 2016
- 원문 바로보기
In December 2015, we have installed neutron monitor at the Jang Bogo station in Antarctica. The Jang Bogo station is the second science station which is located at the coast (<TEX>$74^{\circ}\;37.4^{\prime}S$</TEX>, <TEX>$164^{\circ}\;13.7^{\prime}E$</TEX>) of Terra Nova Bay in Northern Victoria Land of Antarctica. A neutron monitor is an instrument to detect neutrons from secondary cosmic rays collided by the atmosphere. The installation of neutron monitor at Jang Bogo station is a part of transferred mission for neutron monitor at McMurdo station of USA. Among 18 tubes of 18-NM64 neutron monitor, we have completed relocation of 6 tubes and the rest will be transferred in December 2017. Currently, comparison of data from both neutron monitors is under way and there is a good agreement between the data. The neutron monitor at Jang Bogo station will be quite useful to study the space weather when the installation is completed.
224
- Admiranto, Agustinus G.
- Journal of astronomy and space sciences
- 33, n.3
- pp.197-205
- 2016
- 원문 바로보기
We investigated two flares in the solar atmosphere that occurred on June 3, 2012 and July 6, 2012 and caused propagation of Moreton and EIT waves. In the June 3 event, we noticed a filament winking which presumably was caused by the wave propagation from the flare. An interesting feature of this event is that there was a reflection of this wave by a coronal hole located alongside the wave propagation, but not all of this wave was transmitted by the coronal hole. Using the running difference method, we calculated the speed of Moreton and EIT waves and we found values of 926 km/s before the reflection and 276 km/s after the reflection (Moreton wave) and 1,127 km/s before the reflection and 46 km/s after the reflection (EIT wave). In the July 6 event, this phenomenon was accompanied by type II and type III solar radio bursts, and we also performed a running difference analysis to find the speed of the Moreton wave, obtaining a value of 988 km/s. The speed derived from the analysis of the solar radio burst was 1,200 km/s, and we assume that this difference was caused by the different nature of the motions in these phenomena, where the solar radio burst was caused by the propagating particles, not waves.
225
- Kim, Sang Hyuk
- Journal of astronomy and space sciences
- 33, n.1
- pp.55-62
- 2016
- 원문 바로보기
Heumgyeonggaknu (欽敬閣漏) is powered by a water-hammering-type water wheel. The technique that maintains the constant speed of the water wheel is assumed to be the one used in the Cheonhyeong (天衡) apparatus in Shui Yun Yi Xiang Tai (水運儀象臺) made by the Northern Song (北宋) dynasty in the 11<sup>th</sup> century. We investigated the history of the development and characteristics of the Cheonhyeong apparatus, and we analyzed ways to transmit the power of Heumgyeonggaknu. In addition, we carried out a conceptual design to systematically examine the power control system. Based on the conceptual design, we built a model for a water wheel control system that could be used in experiments by drawing a 3D model and a basic design.
226
- Kim, Vitaly P.
- Journal of astronomy and space sciences
- 33, n.4
- pp.273-278
- 2016
- 원문 바로보기
December 2009 was one of the quietest (monthly Ap=2) months over the last eight decades. It provided an excellent opportunity to study the day-to-day variability of the F2 layer with the smallest contribution due to geomagnetic activity. With this aim, we analyze hourly values of the F2-layer critical frequency (foF2) recorded at 18 ionosonde stations during the magnetically quietest (Ap=0) days of the month. The foF2 variability is quantified as the relative standard deviation of foF2 about the mean of all the 'zero-Ap' days of December 2009. This case study may contribute to a more clear vision of the F2-layer variability caused by sources not linked to geomagnetic activity. In accord with previous studies, we find that there is considerable 'zero-Ap' variability of foF2 all over the world. At most locations, foF2 variability is presumably affected by the passage of the solar terminator. The patterns of foF2 variability are different at different stations. Possible causes of the observed diurnal foF2 variability may be related to 'meteorological' disturbances transmitted from the lower atmosphere or/and effects of the intrinsic turbulence of the ionosphere-atmosphere system.
227
- Hwang, Junga
- Journal of astronomy and space sciences
- 33, n.4
- pp.279-285
- 2016
- 원문 바로보기
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.
228
- Baliyan, Kiran S.
- Journal of astronomy and space sciences
- 33, n.3
- pp.177-183
- 2016
- 원문 바로보기
Active galactic nuclei (AGN) are too compact to be resolved by any existing optical telescope facility, making it difficult to understand their structure and the emission processes responsible for their huge energy output. However, variability, one of their characteristic properties, provides a tool to probe the inner regions of AGN. Blazars are the best candidates for such a study, and hence a considerable amount of effort is being made to investigate variability in these sources across the electromagnetic spectrum. Here, using the Mt. Abu infrared observatory (MIRO) blazar monitoring program, we present intra-night, inter-night, and long term aspects of the variability in S5 0716+71, 3C66A, and OJ 287. These stars show significant variability on short (a few tens of mins, to a few hours, to a few days) to long term (months to years) timescales. Based on the light travel time argument, the shortest variability timescales (micro-variability) provide upper limits to the size of the emission region. While S5 0716 shows a very high duty cycle of variability (> 80 %), 3C66A shows a much lower intra day variability (IDV) duty cycle (< 20 %). All three show rapid variations within 2.5 to 3.5 hr, which, perhaps, are generated near the vicinity of black holes. Assuming this, estimates of the masses of the black holes are made at ~10<sup>9</sup>, 8×10<sup>8</sup>, and 2.7×10<sup>9</sup> M<sub>⨀</sub> for S5 0716+71, 3C66A, and OJ 287, respectively. Multi-wavelength light-curves for the blazar PKS 1510-089 are discussed to infer the emission processes responsible for the recent flaring episodes in this source.
229
- Yu, Hoi-Fung
- Journal of astronomy and space sciences
- 33, n.2
- pp.109-117
- 2016
- 원문 바로보기
We explain the results of Yu et al. (2015b) of the novel sharpness angle measurement to a large number of spectra obtained from the Fermi gamma-ray burst monitor. The sharpness angle is compared to the values obtained from various representative emission models: blackbody, single-electron synchrotron, synchrotron emission from a Maxwellian or power-law electron distribution. It is found that more than 91% of the high temporally and spectrally resolved spectra are inconsistent with any kind of optically thin synchrotron emission model alone. It is also found that the limiting case, a single temperature Maxwellian synchrotron function, can only contribute up to 58<sup>+23</sup><sub>−18</sub>% of the peak flux. These results show that even the sharpest but non-realistic case, the single-electron synchrotron function, cannot explain a large fraction of the observed spectra. Since any combination of physically possible synchrotron spectra added together will always further broaden the spectrum, emission mechanisms other than optically thin synchrotron radiation are likely required in a full explanation of the spectral peaks or breaks of the GRB prompt emission phase.
230
- Jung, Jongil
- Journal of astronomy and space sciences
- 33, n.1
- pp.21-28
- 2016
- 원문 바로보기
Caves can serve as major outposts for future human exploration of the Moon and Mars. In addition, caves can protect people and electronic equipment from external hazards such as cosmic ray radiation and meteorites impacts and serve as a shelter. Numerous pit craters have been discovered on the Moon and Mars and are potential entrances to caves; the principal topographic features of pit craters are their visible internal floors and pits with vertical walls. We have devised two topographical models for investigating the relationship between the topographical characteristics and the inner void of pit craters. One of our models is a concave floor void model and the other is a convex floor tube model. For each model, optical photographs have been obtained under conditions similar to those in which optical photographs have been acquired for craters on the Moon and Mars. Brightness profiles were analyzed for determining the profile patterns of the void pit craters. The profile patterns were compared to the brightness profiles of Martian pit craters, because no good-quality images of lunar pit craters were available. In future studies, the model profile patterns will be compared to those of lunar pit craters, and the proposed method will likely become useful for finding lunar caves and consequently for planning lunar bases for manned lunar expeditions.