http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Nicholas Ssessanga (검색결과 9 건)
- 무료
- 기관 내 무료
- 유료
-
Regional Optimization of the IRI-2012 Output (TEC, foF2) by Using Derived GPS-TEC
Nicholas Ssessanga,김용하,김은솔,김재민 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.10
Accurate measurement and determination of the state of the ionosphere has become a key point as ground-based communication systems become more space dependent. However, due to limited infrastructure, a number of global models have been developed with extensive interpolation techniques to comprehensively describe ionospheric dynamics. As a result, most global models do not perform adequately in regions with a paucity of ionospheric measurements. In this paper, the most recent International Reference Ionosphere (IRI-2012) model output, Total Electron Content (TEC) and F2 layer critical frequency (foF2), are optimized (over a range of 120 E − 150 E and 20 N − 50 N in longitude and latitude, respectively). To obtain the optimal solution, we adjust two input parameters, the 12-month running mean sun spot number (R12) and the ionospheric index (IG12), in relation to the derived Global Positioning System (GPS) vertical TEC (VTEC). The results are compared to the measured TEC and foF2 from GPS receivers and ionosondes, respectively. The analysis shows that the modified IRI-2012 model is more accurate at estimating both the TEC and the foF2 values than the original model during days of geomagnetic quiet and disturbance.
-
-
-
Storm Sudden Commencements Without Interplanetary Shocks
Wooyeon Park,Jeongwoo Lee,Yu Yi,Nicholas Ssessanga,Suyeon Oh 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.3
Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism – Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than –30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.
-
Storm Sudden Commencements Without Interplanetary Shocks
Wooyeon Park,이정우,이유,Nicholas Ssessanga,SU YEON OH 한국우주과학회 2015 Journal of Astronomy and Space Sciences Vol.32 No.3
Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism – Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than –30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.
-
홍준석,김용하,정종균,Nicholas Ssessanga,곽영실 한국우주과학회 2017 Journal of Astronomy and Space Sciences Vol.34 No.1
In South Korea, there are about 80 Global Positioning System (GPS) monitoring stations providing total electron content (TEC) every 10 min, which can be accessed through Korea Astronomy and Space Science Institute (KASI) for scientific use. We applied the computerized ionospheric tomography (CIT) algorithm to the TEC dataset from this GPS network for monitoring the regional ionosphere over South Korea. The algorithm utilizes multiplicative algebraic reconstruction technique (MART) with an initial condition of the latest International Reference Ionosphere-2016 model (IRI-2016). In order to reduce the number of unknown variables, the vertical profiles of electron density are expressed with a linear combination of empirical orthonormal functions (EOFs) that were derived from the IRI empirical profiles. Although the number of receiver sites is much smaller than that of Japan, the CIT algorithm yielded reasonable structure of the ionosphere over South Korea. We verified the CIT results with NmF2 from ionosondes in Icheon and Jeju and also with GPS TEC at the center of South Korea. In addition, the total time required for CIT calculation was only about 5 min, enabling the exploration of the vertical ionospheric structure in near real time.
-
Chalachew Kindie Mengist,김용하,Nicholas Ssessanga,김정헌 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.7
In this study, we develop a time-dependent three-dimensional regional ionosphere model over the Korean peninsula (32° N - 42° N, 122° E - 132° E, and 100 - 1000 km in altitude) by using data assimilation technique. Slant total electron content (STEC) data from 80 global positioning system (GPS) receiver stations on the Korean peninsula are assimilated into International Reference Ionosphere (IRI) 2016 as a background model. The assimilated results are validated with independent sources of electron density information: 1) GPS STEC not used in the assimilation and 2) f o F2 and bottom side electron density profiles from two ionosondes. Results show that data assimilation estimates the observations with a 3 - 41% improvement over the climatic IRI 2016 model.
-
Storm Sudden Commencements Without Interplanetary Shocks
Park, Wooyeon,Lee, Jeongwoo,Yi, Yu,Ssessanga, Nicholas,Oh, Suyeon The Korean Space Science Society 2015 Journal of Astronomy and Space Sciences Vol.32 No.3
Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism - Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than -30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.
-
Kim Gwang Su,Kim Yong Ha,Choi Byung-Kyu,Hong Junseok,Ssessanga Nicholas 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.8
The four-dimensional variational (4D-VAR) technique, originally developed for weather forecasting applications, has been utilized in a data-assimilated model to estimate rocket exhaust emission from observed ionospheric disturbances. In this study, we improved the 4D-VAR method by utilizing a more realistic chemical model in the ionosphere and applied it to characterize ionosphere disturbances caused by the Hwasung-15 (H-15) rocket exhaust chemicals. The H-15 rocket was launched southeastward from North Korea at 18:17 UT on 28 November 2017. During the first hours of the launch, the total electron content (TEC) derived from the Korean ground-based GNSS receiver network exhibited ionospheric disturbances along the Rocket’s trajectory. The disturbances were most distinct along the GLONASS (Global Orbiting Navigational Satellite System) line of site. By assimilating the measured TEC data into the 4D-VAR model, we were able to characterize the ionospheric depletion and recovery with respect to the standard ionospheric model, IRI-2016. In addition, the rocket exhaust emissions were estimated to be ~ 1.5 × 1027 molecules per sec, with a number ratio of 2:1 for water to hydrogen in the rocket’s exhaust gas.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
