• Journal of Astronomy and Space Sciences
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• v.35 no.3
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• pp.185-193
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• 2018

Jang Bogo Station (JBS), the second Korean Antarctic research station, was established in Terra Nova Bay, Antarctica ($74.62^{\circ}S$ $164.22^{\circ}E$) in February 2014 in order to expand the Korea Polar Research Institute (KOPRI) research capabilities. One of the main research areas at JBS is space environmental research. The goal of the research is to better understand the general characteristics of the polar region ionosphere and thermosphere and their responses to solar wind and the magnetosphere. Ground-based observations at JBS for upper atmospheric wind and temperature measurements using the Fabry-Perot Interferometer (FPI) began in March 2014. Ionospheric radar (VIPIR) measurements have been collected since 2015 to monitor the state of the polar ionosphere for electron density height profiles, horizontal density gradients, and ion drifts. To investigate the magnetosphere and geomagnetic field variations, a search-coil magnetometer and vector magnetometer were installed in 2017 and 2018, respectively. Since JBS is positioned in an ideal location for auroral observations, we installed an auroral all-sky imager with a color sensor in January 2018 to study substorms as well as auroras. In addition to these observations, we are also operating a proton auroral imager, airglow imager, global positioning system total electron content (GPS TEC)/scintillation monitor, and neutron monitor in collaboration with other institutes. In this article, we briefly introduce the observational activities performed at JBS and the preliminary results of these observations.

• Information and Communications Magazine
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• v.15 no.9
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• pp.97-106
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• 1998

It is crucial to predict the variabilities of the near-earth space environment associated with the solar activity, which cause enormous socio-economic impacts on mankind. The geomagnetic storm prediction scheme adopted in this study is designed to predict such variabilities in terms of the geomagnetic indices, AE and Dst, the cross-polar cap potential difference, the energy dissipation rate over the polar ionosphere and associated temperature increase in the thermosphere. The prediction code consists of two parts; prediction of the solar wind and interplanetary magnetic field based upon actual flare observations and estimation of various electrodynamic quantities mentioned above from the solar wind-magnetosphere coupling function 'epsilon' which is derivable through the predicted solar wind parameters. As a test run, the magnetic storm that occurred in early November, 1993, is simulated and the results are compared with the solar wind and the interplanetary magnetic field measured by the Japanese satellite, Geotail, and the geomagnetic indices obtained from ground magnetic observatories. Although numerous aspects of the code are to be further improved, the comparison between the simulated results and the actual measurements encourages us to use this prediction scheme as the first appoximation in forecasting the disturbances of the near-earth space environment associated with solar flares.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.125.1-125.1
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• 2012

The wave number 4 (wave-4) and wave number 3 (wave-3) longitudinal structures in the thermospheric neutral mass density are understood as tidal structures driven by diurnal eastward-propagating zonal wave number 3 (DE3) and wave number 2 (DE2) tides, respectively. However, those structures have been identified using data from limited time periods, and the consistency and recurrence of those structures have not yet been examined using long-term observation data. We examine the persistence of those structures by analyzing the neutral mass density data for the years 2001-2008 taken by the CHAllenging Minisatellite Payload (CHAMP) satellite. During years of low solar activity, the amplitude of the wave-4 structure is pronounced during August and September, and the wave-4 phase shows a consistent eastward phase progression of $90^{\circ}$ within 24 h local time in different months and years. During years of high solar activity, the wave-4 amplitude is small and does not show a distinctive annual pattern, but the tendency of the eastward phase shift at a rate of $90^{\circ}$/24 h exists. Thus the DE3 signature in the wave-4 structure is considered as a persistent feature. The wave-3 structure is a weak feature in most months and years. The amplitude and phase of the wave-3 structure do not show a notable solar cycle dependence. Among the contributing tidal modes to the wave-3 structure, the DE2 amplitude is most pronounced. This result may suggest that the DE2 signature, although it is a weak signature, is a perceivable persistent feature in the thermosphere.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.231-239
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• 2013

To identify seasonal and latitudinal variations of F2 layer during magnetic storm, we examine the change of daily averages of foF2 observed at Kokubunji and Hobart during high (2000~2002) and low (2006~2008) solar activity intervals. It is found that geomagnetic activity has a different effect on the ionospheric F2-layer electron density variation for different seasons and different latitudes. We, thus, investigate how the change of geomagnetic activity affects the ionospheric F2-layer electron density with season and latitude. For this purpose, two magnetic storms occurred in equinox (31 March 2001) and solstice (20 November 2003) seasons are selected. Then we investigate foF2, which are observed at Kokubunji, Townsville, Brisbane, Canberra and Hobart, Dst index, Ap index, and AE index for the two magnetic storm periods. These observatories have similar geomagnetic longitude, but have different latitude. Furthermore, we investigate the relation between the foF2 and the [O]/[$N_2$] ratio and TEC variations during 19-22 November 2003 magnetic storm period. As a result, we find that the latitudinal variations of [O]/[$N_2$] ratio and TEC are closely related with the latitudinal variation of foF2. Therefore, we conclude that the seasonal and latitudinal variations of foF2 during magnetic storm are caused by the seasonal and latitudinal variations of mean meridional circulation of the thermosphere, particularly upwelling and downwelling of neutral atmosphere during magnetic storm.

• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.235-242
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• 2018

A Fabry-Perot interferometer (FPI) for mesospheric observations was installed at King Sejong Station ($62.2^{\circ}S$, $58.9^{\circ}W$) in Antarctica in 2017. For the initial validation of the FPI measurements, we compare neutral wind data recorded with the FPI with those from a Meteor Radar (MR) located nearby. The overall characteristics of the FPI and MR winds of both OH 892.0 nm (87 km) and OI 557.7 nm (97 km) airglow layers are similar. The FPI winds of both layers generally match the MR winds well on the observed days, with a few exceptions. The correlation analysis of the FPI and MR wind data shows that the correlation coefficients for the zonal winds at 87 and 97 km are 0.28 and 0.54, respectively, and those for the meridional winds are 0.36 and 0.54, respectively. Based on the assumption that the distribution of the airglow emissions has a Gaussian function with respect to the altitude, we calculated the weighted mean winds from the MR wind profile and compared them with the FPI winds. By adjusting the peak height and full width at half maximum of the Gaussian function, we determined the change of the correlation between the two winds. The best correlation for the OH and OI airglow layers was obtained at a peak height of 88-89 km and 97-98 km, respectively.

• Journal of Astronomy and Space Sciences
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• v.38 no.4
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• pp.203-215
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• 2021

The auroral observation has been started at Jang Bogo Station (JBS), Antarctica by using a visible All-sky camera (v-ASC) in 2018 to routinely monitor the aurora in association with the simultaneous observations of the ionosphere, thermosphere and magnetosphere at the station. In this article, the auroral observations are introduced with the analysis procedure to recognize the aurora from the v-ASC image data and to compute the auroral occurrences and the initial results on their spatial and temporal distributions are presented. The auroral occurrences are mostly confined to the northern horizon in the evening sector and extend to the zenith from the northwest to cover almost the entire sky disk over JBS at around 08 MLT (magnetic local time; 03 LT) and then retract to the northeast in the morning sector. At near the magnetic local noon, the occurrences are horizontally distributed in the northern sky disk, which shows the auroral occurrences in the cusp region. The results of the auroral occurrences indicate that JBS is located most of the time in the polar cap near the poleward boundary of the auroral oval in the nightside and approaches closer to the oval in the morning sector. At around 08 MLT (03 LT), JBS is located within the auroral oval and then moves away from it, finally being located in the cusp region at the magnetic local noon, which indicates that the location of JBS turns out to be ideal to investigate the variabilities of the poleward boundary of the auroral oval from long-term observations of the auroral occurrences. The future plan for the ground auroral observations near JBS is presented.

• Journal of Astronomy and Space Sciences
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• v.40 no.1
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• pp.1-10
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• 2023

Korea Polar Research Institute (KOPRI) and Korea Astronomy and Space Institute (KASI) have been participating in the European Incoherent Scatter (EISCAT) Scientific Association as an affiliate institution in order to observe the polar ionosphere since 2015. During the period of December 16-21, 2016 and January 3-9, 2018, the observations for the polar ionospheric parameters such as the electron density profiles, ion drift, and electron/ion temperature are carried out in the polar cap/cusp region by the EISCAT Svalbard radar (ESR). The purpose of the observations is to investigate the characteristic of the winter ionosphere in the dayside polar cap/cusp region. In this paper, we briefly report the results of the ESR observations for winter daytime ionosphere and also the simultaneous observations for the ionosphere-thermosphere system together with the balloon-borne instrument High-Altitude Interferometer WIND Experiment (HIWIND) performed by the High Altitude Observatory (HAO), National Center for Atmospheric Research (NCAR). We further introduce our research activities using long-term EISCAT observations for the occurrence of ion upflow and the climatology of the polar ionospheric density profiles in comparison with the mid-latitude ionosphere. Finally, our future research plans will briefly be introduced.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.94-108
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• 1997

The temperature of the upper thermosphere is generally varied with the solar activity, and largely with geomagnetic activity in the high latitude. The data analyzed in this study are acquired at two ground stations, Thule Air Base($76,5{deg} N, 68.4{deg} W, A = 86{deg}$) and $S{psi}ndre Str{psi}mfjord (67.0{deg} N, 50.9{deg} W, A = 74{deg}$), Greenland. Both stations are located in the high latitude not only geographically but also geomagnetically. The terrestrial night glow at 6300 ${angs}$ from atomic oxygen has been observed from the two ground-based Fabry-Perot interferometers, during periods of 1986~1991 in Thule Air Base and 1986~1994 in $S{psi}ndre Str{psi}mfjord$. Some features noted in this study are as follows: (1) The correlation between the solar activity and the measured thermospheric temperature is highest in the case of $3{leq}Kp{leq}4$ in Thule, and increases with the geomagnetic activity in $S{psi}ndre Str{psi}mfjord$. (2) The measured temperatures at Thule is generally higher than those at $S{psi}ndre Str{psi}mfjord$, but the latter shows steeper slope with the solar activity. (3) The harmonic analysis shows that the diurnal variation(24hrs) is the main feature of the daily temperature variation with a temperature peak at about 13-14 LT (LT=UT-4). However, the semi-diurnal variation is evident during the period of weak solar activity. (4) Generally the predicted temperatures from both MSIS86 and VSH models are lower than the measured temperature, and this discrepancy grows as the solar activity increases. Therefore, we urge modelers to develope a new thermospheric model utilizing broader sets of measurements, especially for high solar activity.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.305-318
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• 2002

We have constructed two flight models of airglow photometer system (AGP) to be onboard Korea Sounding Rocket-III (KSR-III) for detection of MUV dayglow above the Korean peninsular. The AGP system is designed to detect dayglow emissions of OI 2972${\AA}$, $N_2$ VK(0,6) 2780${\AA}$, $N_2$ 2PG 3150${\AA}$ and background 3070${\AA}$ toward the horizon at altitudes between 100 km and 300 km. The AGP system consists of a photometer body, a baffle an electronic control unit and a battery unit. The MUV dayglow emissions enter through a narrow band interference filter and focusing lens of the photometer, which contains an ultraviolet sensitive photomultiplier tube. The photometer is equipped with an in-flight calibration light source on a circular plane that will rotate at the rocket's apogee. A bane tube is installed at the entry of the photometer in order to block strong scattering lights from the lower atmosphere. We have carried out laboratory measurements of sensitivity and in-flight calibration light source for the AGP flight models. Although absolute sensitivities of the AGP flight models could not be determined in the country, relative sensitivities among channels are well measured so that observation data during rocket flight in the future can be analyzed with confidence.

• Journal of Astronomy and Space Sciences
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• v.24 no.1
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• pp.55-68
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• 2007

We carried out a validation study on AURIC FUV/EUV dayglow calculation with $OII\;834{\AA},\;OI\;989{\AA},\;OI\;1027{\AA},\;NII\;1085{\AA},\;NI\;1134{\AA},\;NI\;1200{\AA},\;OI\;1304{\AA},\;OI\;1356{\AA}$ dayglows observed by STP78-1 satellite. Comparison between calculated and observed values indicates that they are in agreement within about 20% for dayglows of $OII\;834{\AA},\;OI\;1027{\AA},\;NI\;1200{\AA},\;OI\;1304{\AA}$. However, the calculated intensities of $OI\;989{\AA},\;NII\;1085{\AA},\;NI\;1134{\AA}$ are only 42, 74 and 45% of the observed values, respectively, showing serious differences from the observation. It was surmised that the differences in $OI\;989{\AA}\;and\;NI\;1134{\AA}$ are due to incomplete calculation of radiative transfer and uncertain photochemical processes in AURIC model, respectively. The difference in $NII\;1085{\AA}$ is conjectured to be due to variation of the input solar EUV flux rather than due to AURIC model itself. For up-looking dayglows from the satellite, the calculated values from AURIC are all less than those of STP78-1, which may imply that AURIC model does not include dayglow contribution from regions below the satellite altitude when it computes dayglows in up-looking direction. The differences are particularly serious for $OI\;989{\AA},\;NI\;1134{\AA},\;NI\;1200{\AA}$ dayglows. The calculated latitudinal variation of $OII\;834{\AA}$ dayglow is also significantly different from the observed one, especially at mid-latitude regions. This may be due to inability of MSISE-90 (in input of AURIC) to simulate oxygen atom densities at mid-latitudes during auroral storms at those days of STP78-1 observations. Our findings of the validation study should be resolved when AURIC model is revised in future.