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Limitations of Electromagnetic Ion Cyclotron Wave Observations in Low Earth Orbit
황정아,김향표,박재흥,이재진 한국우주과학회 2018 Journal of Astronomy and Space Sciences Vol.35 No.1
Pc1 pulsations are geomagnetic fluctuations in the frequency range of 0.2 to 5 Hz. There have been several observations of Pc1 pulsations in low earth orbit by MAGSAT, DE-2, Viking, Freja, CHAMP, and SWARM satellites. However, there has been a clear limitation in resolving the spatial and temporal variations of the pulsation by using a single-point observation by a single satellite. To overcome such limitations of previous observations, a new space mission was recently initiated, using the concept of multi-satellites, named the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE). The SNIPE mission consists of four nanosatellites (~10 kg), which will be launched into a polar orbit at an altitude of 600 km (TBD) in 2020. Four satellites will be deployed in orbit, and the distances between each satellite will be controlled from 10 to 1,000 km by a highend formation-flying algorithm. One of the possible science targets of the SNIPE mission is observing electromagnetic ion cyclotron (EMIC) waves. In this paper, we report on examples of observations, showing the limitations of previous EMIC observations in low earth orbit, and suggest possibilities to overcome those limitations through a new mission.
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황정아,김향표,박영덕 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.4
Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth’s geomagnetic filed by space weather, we use the international quiet days’ data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components’ quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation’s amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth’s atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.
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Comparison of K-index Calculations between Several Geomagnetic Stations during IQDs and IDDs
황정아,김향표,박영득 한국우주과학회 2013 Journal of Astronomy and Space Sciences Vol.30 No.3
BOH magnetometer was installed at Mt. Bohyun in 2007 and has provided continuous dataset for 3-axis geomagnetic field over the South Korea. We have calculated real-time K-index based on BOH magnetic field data using well-known FMI method. Local K-index is calculated eight times a day, per every three hours. To calculate K-index, it is critical to get the Quiet Day Curve (QDC). For QDC calculation, we take the previous one month’s average of H-component. In this paper, we compared four geomagnetic stations’ magnetic field data over South Korea and Japan and K-indices of each stations; Bohyun, Gangneung,Jeju, and Kakioka for two years data, 2011-2012. To investigate the difference depending on the latitude, longitude and local time in more detail, we compare K-index on International Quiet Days (IQDs) and International Disturbed Days (IDDs). As a result, we report the correlation between local K-indices are higher than those between Kp and local K-indices, and the correlation is much better after sunset than after sunrise. As the geomagnetic activity becomes stronger, the correlation between the local K-indices and global Kp-index become higher.
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황정아,독고경환,최은진,박종선,김경찬,김향표 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.1
There has been a rapid increase of the concern on the space radiation effect on pilots, crew and passengers at the commercialaircraft altitude (~ 10 km) recently. It is because domestic airline companies, Korean Air and Asiana Airlines have just begunoperating the polar routes over the North Pole since 2006 and 2009 respectively. CARI-6 and CARI-6M are commonly usedspace radiation estimation programs which are provided officially by the U.S. federal aviation administration (FAA). In thispaper, the route doses and the annual radiation doses for Korean pilots and cabin crew were estimated by using CARI-6Mbased on 2012 flight records. Also the modeling concept was developed for our own space radiation estimation program whichis composed of GEANT4 and NRLMSIS00 models. The GEANT4 model is used to trace the incident particle transports in theatmosphere and the NRLMSIS00 model is used to get the background atmospheric densities of various neutral atoms at theaircraft altitude. Also presented are the results of simple integration tests of those models and the plan to include the spaceweather variations through the solar proton event (SPE) prediction model such as UMASEP and the galactic cosmic ray (GCR)prediction model such as Badhwar-O’Neill 2010.
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