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1984년 ~ 2025년까지 1,255 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 : 1,255건 (DB Construction : 1,255 Articles)
총 게시글 1,255건
페이지 26/126
251
- Song, Yuzhe
- Journal of astronomy and space sciences
- 33, n.2
- pp.69-73
- 2016
- 원문 바로보기
We use the non-stationary three dimensional two-layer outer gap model to explain gamma-ray emissions from a pulsar magnetosphere. We found out that for some pulsars like the Geminga pulsar, it was hard to explain emissions above a level of around 1 GeV. We then developed the model into a non-stationary model. In this model we assigned a power-law distribution to one or more of the spectral parameters proposed in the previous model and calculated the weighted phase-averaged spectrum. Though this model is suitable for some pulsars, it still cannot explain the high energy emission of the Geminga pulsar. An Inverse-Compton Scattering component between the primary particles and the radio photons in the outer magnetosphere was introduced into the model, and this component produced a sufficient number of GeV photons in the spectrum of the Geminga pulsar.
252
- Hegai, Valery V.
- Journal of astronomy and space sciences
- 33, n.3
- pp.207-210
- 2016
- 원문 바로보기
Under the assumption of the presence of a medium-scale E × B drift vortex of plasma in the daytime midlatitude F region, and using a simplified ionospheric model, we demonstrate that the E × B drift produces noticeable perturbations in the horizontal distribution of the plasma density in the upper F region. The pattern of ion density perturbations shows two separate medium scale domains of enhanced and reduced ion density with respect to the background. The E × B drift does not produce multiple small-scale ion density irregularities through plasma mixing because of the suppression effect of the field-aligned ambipolar plasma diffusion.
253
- Dolch, Timothy
- Journal of astronomy and space sciences
- 33, n.3
- pp.167-172
- 2016
- 원문 바로보기
We used the 4 m Discovery Channel Telescope (DCT) at Lowell observatory in 2014 to observe the Guitar Nebula, an Hα bow-shock nebula around the high-velocity radio pulsar B2224+65. Since the nebula's discovery in 1992, the structure of the bow-shock has undergone significant dynamical changes. We have observed the limb structure, targeting the 'body' and 'neck' of the guitar. Comparing the DCT observations to 1995 observations with the Palomar 200-inch Hale telescope, we found changes in both spatial structure and surface brightness in the tip, head, and body of the nebula.
254
- 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.
255
- 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.
256
- Kil, Hyosub
- Journal of astronomy and space sciences
- 32, n.1
- pp.13-19
- 2015
- 원문 바로보기
Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations), vertical plumes (radar observations), and emission-depletion bands elongated in the north-south direction (optical observations). However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a 'shell' structure. This paper reviews the development of the concepts of 'bubble' and 'shell' in this context.
257
- Lee, Jeongwoo
- Journal of astronomy and space sciences
- 32, n.2
- pp.101-112
- 2015
- 원문 바로보기
Magnetic reconnection is a fundamental process occurring in a wide range of astrophysical, heliospheric and laboratory plasmas. This process alters magnetic topology and triggers rapid conversion of magnetic energy into thermal heating and nonthermal particle acceleration. Efforts to understand the physics of magnetic reconnection have been made across multiple disciplines using remote observations of solar flares and in-situ measurements of geomagnetic storms and substorms as well as laboratory and numerical experiments. This review focuses on the progress achieved with solar flare observations in which most reconnection-related signatures could be resolved in both space and time. The emphasis is on various observable emission features in the low solar atmosphere which manifest the coronal magnetic reconnection because these two regions are magnetically connected to each other. The research and application perspectives of solar magnetic reconnection are briefly discussed and compared with those in other plasma environments.
258
- Son, Ju Young
- Journal of astronomy and space sciences
- 32, n.3
- pp.221-228
- 2015
- 원문 바로보기
To protect and manage the Korean space assets including satellites, it is important to have precise positions and orbit information of each space objects. While Korea currently lacks optical observatories dedicated to satellite tracking, the Korea Astronomy and Space Science Institute (KASI) is planning to establish an optical observatory for the active generation of space information. However, due to geopolitical reasons, it is difficult to acquire an adequately sufficient number of optical satellite observatories in Korea. Against this backdrop, this study examined the possible locations for such observatories, and performed simulations to determine the differences in precision of optical orbit estimation results in relation to the relative baseline distance between observatories. To simulate more realistic conditions of optical observation, white noise was introduced to generate observation data, which was then used to investigate the effects of baseline distance between optical observatories and the simulated white noise. We generated the optical observations with white noise to simulate the actual observation, estimated the orbits with several combinations of observation data from the observatories of various baseline differences, and compared the estimated orbits to check the improvement of precision. As a result, the effect of the baseline distance in combined optical GEO satellite observation is obvious but small compared to the observation resolution limit of optical GEO observation.
259
- Son, Ju Young
- Journal of astronomy and space sciences
- 32, n.3
- pp.229-235
- 2015
- 원문 바로보기
We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.
260
- Kim, Eunsol
- Journal of astronomy and space sciences
- 32, n.2
- pp.121-125
- 2015
- 원문 바로보기
At the suggestion of the NASA Meteoroid Environment Office (NASA/MEO), which promotes lunar impact monitoring worldwide during NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) mission period (launched Sept. 2013), we set up a video observation system for lunar impact flashes using a 16-inch educational telescope at Chungnam National University. From Oct. 2013 through Apr. 2014, we recorded 80 hours of video observation of the unilluminated part of the crescent moon in the evening hours. We found a plausible candidate impact flash on Feb. 3, 2014 at selenographic longitude <TEX>$2.1^{\circ}$</TEX> and latitude <TEX>$25.4^{\circ}$</TEX>. The flash lasted for 0.2 s and the light curve was asymmetric with a slow decrease after a peak brightness of <TEX>$8.7{\pm}0.3mag$</TEX>. Based on a star-like distribution of pixel brightness and asymmetric light curve, we conclude that the observed flash was due to a meteoroid impact on the lunar surface. Since unequivocal detection of an impact flash requires simultaneous observation from at least two sites, we strongly recommend that other institutes and universities in Korea set up similar inexpensive monitoring systems involving educational or amateur telescopes, and that they collaborate in the near future.