• Journal of Astronomy and Space Sciences
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• 제38권4호
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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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• 제27권3호
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• pp.189-194
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• 2010

In this paper we have investigated latitudinal variations of the poleward boundary of the nightside auroral oval when the magnetosphere is hit by an enhanced solar wind dynamic pressure front. We used precipitating particle data obtained from Defense Meteorological Satellite Program satellites to identify the locations of the boundary before and after enhanced pressure impacts. The boundary locations are represented by a parameter called "b5e". After performing the analysis for a number of events, we found that the basic effect of the solar wind pressure increase impact is often (but not always) to move the poleward boundary of the nightside auroral oval poleward. However, this effect can be often modified by other factors, such as simultaneous variations of the interplanetary magnetic field with a pressure increase, and thus the boundary response is not necessarily a poleward shift in many cases. We demonstrate this with specific examples, and discuss other possible complicating factors.

• 천문학회지
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• 제28권1호
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• pp.89-95
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• 1995

We examined a total of 166 images of $3.5{\mu}m\;H_3^+$ emission in the auroral regions of Jupiter observed with the Protocam on IRTF in 1991 and 1992, and found that 30 images contain a clearly isolated small emission patch in the vicinity of the northern auroral regions. Two different time sequences of the images show the small patches at the dusk limb in the range of System III longitudes from $270^{\circ}\;through\;0^{\circ}\;to\;90^{circ}$. The small patches in one sequence of the images, which were taken at 10 phase between $240^{\circ}\;and\;260^{\circ}$, may be related to the 10 flux tube, similarly suggested by Connerney et al. (1993). However, the small patches in the other sequence are separated from Io as much as $80^{\circ}$ in longitude. The positions of the small patches in both sequences are deviated equatorward from the 10 footprint oval by $5^{\circ}-8^{\circ}$ latitude in the longitudinal range of $270^{\circ}-360^{\circ}$. A significant modification is required in current Jovian magnetic field models near the Jupiter's surface if the small patches are produced at the foot of the 10 flux tube.

• 천문학회보
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• 제40권1호
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• pp.60.2-60.2
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• 2015

Since its detection in 1980, the $8-{\mu}m$ north-polar brightening of $CH_4$ on Juptier has not moved from $180^{\circ}$ (SysIII) longitude. The $8-{\mu}m$ $CH_4$ brightening is mostly thermal and very similar to that of $13-{\mu}m$ $C_2H_2$ emissions, but the morphology of these hydrocarbon north-polar brightenings are very different from that of the $3-{\mu}m$ $H_3{^+}$ auroral oval suggesting a significantly different excitation process yet unknown heating mechanism. Recently, Kim et al. (submitted to Icarus, 2015) found that that the center of the $3-{\mu}m$ $CH_4$ northern bright spot is located at ${\sim}200^{\circ}$ (SysIII) longitude, which is ${\sim}20^{\circ}$ west from the center of the $8-{\mu}m$ north-polar bright spot, and it does not coincide with the $3-{\mu}m$ $H_3{^+}$ bright spot. They found significantly high temperatures (500 ~ 850K) from $CH_4$ rotational lines on the $3-{\mu}m$ bright spot above the $1-{\mu}bar$ pressure level, while we find cooler temperatures (<350K) over the the $8-{\mu}m$ spot. They also found that the upper states of the $3-{\mu}m$ $CH_4$ bands are mostly populated by non-thermal excitations, such as auroral particle precipitations and/or Joule heatings in contrast to the $8-{\mu}m$ thermal emission. This finding indicates that the $10-{\mu}m$ hydrocarbon brightening is confined to low altitudes below the $1-{\mu}bar$ level eliminating the long-suggested possibility of direct auroral bombardments while opening a new possibility of dynamical origin for the $10-{\mu}m$ brightening.

• Journal of Astronomy and Space Sciences
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• 제19권2호
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• pp.141-150
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• 2002

전리층은 우주환경의 변화에 매우 중요한 역할을 하고 있다. 특히 전기전도도 분포에 관한 정보는 자기권-전리층 상호작용을 이해하는데 필수적이다. 이러한 요구에 부응해서 전기전도도를 구하려는 다양한 시도가 있었다. 본 연구에서는 SuperDARN(Super Dual Auroral Radar Network) 레이더망 중 Goose Bay 및 Stokkseyri 레이더에서 관측한 전기장과 Greenland의 서부해안에 설치된 지자기 관측소에서 동시에 얻은 지상 지자기 기록을 이용하여 전기전도도를 추정하였다. 또한 전리층을 흐르는 전류를 무한판상으로 가정하고 Biot-Savart 및 Ohm의 법칙을 적용하여 Hall 및 Pedersen 전기전도도를 추정하였다. 예상한대로 Hall 전기전도도는 오로라 제트전류대의 중심을 따라 상당히 강화됨을 알 수 있었다. 그러나 Pedersen 전기전도도는 광범위한 지역에 서 음의 값이 나타났다. 이러한 문제를 보완하기 위해서 지자기 변화 성분인 ${\Delta}D$에 연자기력선 전류의 효과를 고려하였다. 그 결과 이전에 음으로 나타난 지역이 상당히 감소되었다. 따라서 지상 지자기 변화 자료와 레이더에서 관측된 전기장을 이용해서 전기전도도를 구하는 경우 연자기력선 전류의 효과를 고려해야 한다.

• 천문학논총
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• 제30권2호
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• pp.61-64
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• 2015

The brightness of Io's magnetic footprint, an indicator of electromagnetic interaction at the satellite, appears to be strongly connected to the satellite's distance from the plasma equator. As a result, the brightest footprints were detected when Io is near the interception location between the satellite's orbital plane and the plasma equator. However, volcanic activities on Io show strong correlation with the equatorward shift of Jupiter's main auroral oval, consequently causing the disappearance of Io's footprint. The same conclusion was suggested via the observation of Jupiter's hectometric radio emission, called HOM, which closely corresponds to Jupiter's auroral activity. The plasma environment near the Jovian satellites was found to vary significantly at different observational epochs. The electron density increased by approximately a factor of three from the Voyager epoch (1979) to the Galileo epoch (1995), while the electron density was found to be significantly higher (~ 5 times) in the Cassini epoch (2001). In this current study, the magnetic footprints were clearly brighter ten years ago (from peak brightness in 1998-2001) than the footprints detected in 2007. For volcanic activities on Io in 2007, there are two clear activities in February and late May. The magnetic footprint appeared to be dimmer in March 2007, expected to be the result of volcano activities in Feb 2007. However, the magnetic footprint brightness in June appeared to be slightly brighter than the footprints observed in May. The reason could be the time delay between the brightening of the sodium nebula on approximately May 31st and, a while later, the enhancement of flux tube content peaking on approximately June 5th. On the other hand, Io's magnetic footprints were observed during June 1st - 10th when they may not yet have been affected by the increase in mass outflow due to the increase of plasma density.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.143-156
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• 2020

Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5-25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.245-250
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• 2017

As a part of collaborative efforts to understand ionospheric irregularities, the Korea ionospheric scintillation sites (KISS) network has been built based on global positioning system (GPS) receivers with sampling rates higher than 1 Hz. We produce the rate of TEC index (ROTI) to represent GPS TEC fluctuations related to ionospheric irregularities. In the KISS network, two ground-based GPS sites at Kiruna (marker: KIRN; geographic: $67.9^{\circ}$ N, $21.4^{\circ}$ E; geomagnetic: $65.2^{\circ}$ N) and Chuuk (marker: CHUK; geographic: $7.5^{\circ}$ N, $151.9^{\circ}$ E; geomagnetic: $0.4^{\circ}$ N) were selected to evaluate the ROTI value for ionospheric irregularities during the occurrence of the 2015 St. Patrick's Day storm. The KIRN ROTI values in the aurora region appear to be generally much higher than the CHUK ROTI values in the EIA region. The CHUK ROTI values increased to ~0.5 TECU/min around UT=13:00 (LT=23:00) on March 16 in the quiet geomagnetic condition. On March 17, 2015, CHUK ROTI values more than 1.0 TECU/min were measured between UT=9:00 and 12:00 (LT=19:00 and 22:00) during the first main phase of the St. Patrick's Day storm. This may be due to ionospheric irregularities by increased pre-reversal enhancement (PRE) after sunset during the geomagnetic storm. Post-midnight, the CHUK ROTI showed two peaks of ~0.5 TECU/min and ~0.3 TECU/min near UT=15:00 (LT=01:00) and UT=18:00 (LT=04:00) at the second main phase. The KIRN site showed significant peaks of ROTI around geomagnetic latitude=$63.3^{\circ}$ N and MLT=15:40 on the same day. These can be explained by enhanced ionospheric irregularities in the auroral oval at the maximum of AE index

• 천문학회보
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• 제42권1호
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• pp.40.3-41
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• 2017

Korea Astronomy and Space Science Institute The observation of particles and waves using a single satellite inherently suffers from space-time ambiguity. Recently, such ambiguity has often been resolved by multi-satellite observations; however, the inter-satellite distances were generally larger than 100 km. Hence, the ambiguity could be resolved only for large-scale (> 100 km) structures while numerous microscale phenomena have been observed at low altitude satellite orbits. In order to resolve those spatial and temporal variations of the microscale plasma structures on the topside ionosphere, SNIPE mission consisted of four (TBD) nanosatellites (~10 kg) will be launched into a polar orbit at an altitude of 700 km (TBD). Two pairs of satellites will be deployed on orbit and the distances between each satellite will be from 10 to 100 km controlled by a formation flying algorithm. The SNIPE mission is equipped with scientific payloads which can measure the following geophysical parameters: density/temperature of cold ionospheric electrons, energetic (~100 keV) electron flux, and magnetic field vectors. All the payloads will have high temporal resolution (~ 16 Hz (TBD)). This mission is planned to launch in 2020. The SNIPE mission aims to elucidate microscale (100 m-10 km) structures in the topside ionosphere (below altitude of 1,000 km), especially the fine-scale morphology of high-energy electron precipitation, cold plasma density/temperature, field-aligned currents, and electromagnetic waves. Hence, the mission will observe microscale structures of the following phenomena in geospace: high-latitude irregularities, such as polar-cap patches; field-aligned currents in the auroral oval; electro-magnetic ion cyclotron (EMIC) waves; hundreds keV electrons' precipitations, such as electron microbursts; subauroral plasma density troughs; and low-latitude plasma irregularities, such as ionospheric blobs and bubbles. We have developed a 6U nanosatellite bus system as the basic platform for the SNIPE mission. Three basic plasma instruments shall be installed on all of each spacecraft, Particle Detector (PD), Langmuir Probe (LP), and Scientific MAGnetometer (SMAG). In addition we now discuss with NASA and JAXA to collaborate with the other payload opportunities into SNIPE mission.