• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
• /
• pp.25.2-25.2
• /
• 2008

Polar rain is a spatially uniform precipitation of electrons with energies around 100eV that penetrate into the polar cap region where geomagnetic field lines are connected to the Interplanetary Magnetic Fields (IMF). Since their occurrences depend on the IMF sector polarity, they are believed to originate from the field aligned component of the solar wind. However, statistically direct correlation between polar rain and solar wind has not been shown. In this presentation, we examined specifically the IMF strength influence on the polar rain flux variation by classifying of IMF sector polarities. For this study, we employed the polar rain flux data measured by STSAT-1 and compared them with the solar wind parameters obtained from the WIND and ACE satellites. We found the direct mutuality between polar rain flux and IMF strength with correlation coefficient above 0.5. This proportional tendency appears stronger when the northern hemisphere is in the away sector of the IMF, which could be associated with a favorable geometry for magnetic reconnection. Simple particle trajectory simulation clearly shows why polar rain intensity depends on the IMF sector polarity. These results are consistent with the direct entry model of Fairfield et al.(1985), while low correlation coefficient with solar wind density, the similarity between slops of both energy spectra shows that transport process occur without acceleration.

• Journal of Astronomy and Space Sciences
• /
• 제24권2호
• /
• pp.91-98
• /
• 2007

The existence of the North-South asymmetry of the solar activity is widely accepted even though the phenomenon is not yet satisfactorily understood. We have studied the temporal variations in the North-South asymmetry of the sunspot area during the period from May in 1874 to April in 2007. The combined data have been examined for periodicity in the solar activity North-South asymmetry. We have found that (i) solar northern and southern hemispheres show an asymmetric behavior, in terms of a sunspot area, (ii) sunspot areas in northern and southern hemispheres show clearly the 11 year periodicity when they were analyzed separately, as they do when analyzed together, (iii) in addition to the general 11 year periodicity in both northern and southern hemisphere solar activities, there are also noticeable shorter periodicities other than the 11 year periodicity in the asymmetry in North-South activity. Finally, we conclude by pointing out the importance of studying the North-South asymmetry of the solar activity.

• 대기
• /
• 제26권4호
• /
• pp.523-540
• /
• 2016

The effects of satellite observations on large-scale atmospheric circulations in the reanalysis data are investigated by comparing the latest Japanese Meteorological Association's reanalysis data (JRA-55) and its family data, JRA-55 Conventional (JRA-55C). The latter is identical to the former except that satellite observations are excluded during the data assimilation process. Only conventional datasets are assimilated in JRA-55C. A simple comparison revealed a considerable difference in temperature and zonal wind fields in both the stratosphere and troposphere. Such differences are particularly large in the Southern Hemisphere and whole stratosphere where conventional ground-based measurements are limited. The effects of satellite observations on the zonal-mean tropospheric circulations are further examined in terms of the Hadley cell, eddy-driven jet, and mid-latitude storm tracks. In both hemispheres, JRA-55C exhibits slightly weaker and narrower Hadley cell than JRA-55. This is consistent with a weaker diabatic heating in JRA-55C. The eddy-driven jet shows a small difference in its latitudinal location only in the Southern Hemisphere. Likewise, while the Northern-Hemisphere storm tracks are quantitatively similar in the two datasets, Southern-Hemisphere storm tracks are relatively weaker in JRA-55C than in JRA-55. Their difference is comparable to the uncertainty between reanalysis datasets, indicating that satellite data assimilation could yield significant corrections in the zonal-mean circulation in the Southern Hemisphere.

• Journal of Astronomy and Space Sciences
• /
• 제32권4호
• /
• pp.297-304
• /
• 2015

In this study, we documented the midlatitude F2-layer response to five strong geomagnetic storms with minimum Dst < -150 nT that occurred in solar minimum years using hourly values of the F2-layer critical frequency (foF2) from four ionosondes located in different hemispheres. The results were very limited, but they illustrated some peculiarities in the behavior of the F2-layer storm. During equinox, the characteristic ionospheric disturbance patterns over the Japanese station Wakkanai in the Northern Hemisphere and the Australian station Mundaring in the Southern Hemisphere were consistent with the well-known scenario by $Pr{\ddot{o}}lss$ (1993); however, during a December solstice magnetic storm, both stations did not observe any noticeable positive ionospheric disturbances. Over the "near-pole" European ionosonde, clear positive ionospheric storms were not observed during the events, but the "far-from-pole" Southern Hemisphere station Port Stanley showed prominent enhancements in F2-layer peak electron density in all magnetic storms except one. No event produced noticeable nighttime enhancements in foF2 over all four ionosondes.

• 천문학회보
• /
• 제39권2호
• /
• pp.40-40
• /
• 2014

Through KASI, Korean astronomers will have access to the Gemini Observatory starting in 2015. Gemini operates two optical/infrared 8m-class telescopes: one on the northern hemisphere in Hawaii, one on the southern hemisphere in Chile. Both are equipped with state of the art instruments and adaptive optics systems that will be presented. Gemini also offers the opportunity for instrument development and welcomes visiting instruments. In terms of operations, Gemini offers to its partners three ways of applying for time: through semester-basis calls for standard programs, through yearly calls for Large and Long Programs, and through monthly calls for fast turnaround programs. Gemini operates in queue mode (observing for the principal investigators and allowing flexibility in the time domain), as well as in the classical visitor mode (where principal investigators come to the telescope). I will explain the requirements and advantages of all these modes as well as a full update on the Gemini Observatory.

• Ocean Science Journal
• /
• 제40권1호
• /
• pp.45-54
• /
• 2005

The history of investigation of the family Velutinidae from 1776 to the present day is briefly described in the last part of this review; the contemporary system of the family, consisting of 39 species and subspecies, belonging to 17 genera and subgenera, and three subfamilies, is presented here. A biogeographic analysis of the fauna has been made, the history of origin and development of the family, vertical distribution and relation to substrates have been described in this work.

• Journal of Astronomy and Space Sciences
• /
• 제28권1호
• /
• pp.1-7
• /
• 2011

Characteristics of latitude variations of sunspots in the northern and southern hemispheres are investigated using the daily sunspot area and its latitude during the period from 1874 to 2009. Solar magnetic activity is portrayed in the form of sunspot, regions of concentrated fresh magnetic fields observed on the surface of the Sun. By defining center-of-latitude (COL) as an area-weighted latitude, we find that COL is not monotonically decreasing as commonly assumed. In fact, small humps (or short plateaus) between solar minima can be seen around every solar maxima. We also find that when the northern (southern) hemisphere is magnetically dominant, COL is positive (negative), except the solar cycle 23, which may give a hint that these two phenomena are consistently regulated by one single mechanism. As a result of periodicity analysis, we find that several significant periodicities, such as, of ~5.5, ~11, ~49, and ~167 years.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
• /
• pp.308-311
• /
• 2006

This study compared between tropospheric column ozone by applying the SAM method to TOMS and OMI data for northern summer. Tropospheric ozone from the SAM represents a peak over the tropical Atlantic, where it is related with biomass burning. This feature is also seen in the distribution of the model and CO. Additionally, enhancement of the SAM ozone over the Middle East, and South and North America agrees well with the model and CO distribution. However, the SAM results show more ozone than the model results over the northern hemisphere, especially the ocean (e.g. the North Pacific and the North Atlantic). The tropospheric ozone distribution from OMI data shows more ozone than that from TOMS data. This can be caused by different viewing angle, sampling frequency, and a-priori ozone profiles between OMI and TOMS. The correlation between the SAM tropospheric ozone and CO is better than that between the model and CO in the tropics. However, that correlation is reversed in the midlatitude.

• 항공우주기술
• /
• 제11권1호
• /
• pp.103-110
• /
• 2012

천리안 위성 임무 운영 관련하여, 전구(Full Disk: FD) 영상 및 2개의 인접 확장북반구(Extended Northern Hemisphere: ENH) 영상들에 대한 기상 관측 임무와 동서방향 위치유지(East West Station Keeping: EWSK) 기동 임무가 서로 충돌할 경우, EWSK의 시간 이동을 통해 큰 기상영상들의 손실을 줄일 수 있다. 이를 위해 FD 및 2개 ENH 영상의 기상관측임무를 피하는 EWSK 시간 이동에 대해 충돌 확률을 고려한 해석적 방법을 제시하여 이론적 고찰을 수행하였으며, 천리안위성 운영에도 시험적으로 적용하였다. 이론적 고찰 결과와 시험 운영 결과를 종합하여 기상영상 회피 EWSK 시간 이동이 천리안위성 연료 소모에 미치는 영향에 대한 연구 결과를 제시하였다. 본 연구 결과는 천리안 기상 임무 활용의 극대화에 기여할 수 있을 것으로 기대한다.

• 대기
• /
• 제28권3호
• /
• pp.233-245
• /
• 2018

This study explores the Subseasonal-to-Seasonal (S2S) prediction skills of the Northern Hemisphere mid-latitude geopotential height in the Global Seasonal forecasting model version 5 (GloSea5) hindcast experiment. The prediction skills are quantitatively verified for the period of 1991~2010 by computing the Anomaly Correlation Coefficient (ACC) and Mean Square Skill Score (MSSS). GloSea5 model shows a higher prediction skill in winter than in summer at most levels regardless of verification methods. Quantitatively, the prediction limit diagnosed with ACC skill of 500 hPa geopotential height, averaged over $30^{\circ}N{\sim}90^{\circ}N$, is 11.0 days in winter, but only 9.1 days in summer. These prediction limits are primarily set by the planetary-scale eddy phase errors. The stratospheric prediction skills are typically higher than the tropospheric skills except in the summer upper-stratosphere where prediction skills are substantially lower than upper-troposphere. The lack of the summer upper-stratospheric prediction skill is caused by zonal mean error, perhaps strongly related to model mean bias in the stratosphere.