Unmanned magnetometer network observation in the 44th Japanese Antarctic Research Expedition: Initial results and an event study on auroral substorm evolution

In the 44th Japanese Antarctic Research Expedition (JARE-44) during 2003 to 2004, four unmanned magnetometers were deployed in Antarctica to establish a observation network for studying ionospheric and magnetospheric phenomena. Three of them were set about 80 km from Syowa Station, and the fourth was set at Dome Fuji Camp, about 800 km from Syowa. Observations were carried out continuously with a maximum sampling rate of 1 Hz. The purpose of the close network around Syowa was to observe the two-dimensional distribution of the ionospheric equivalent current in a localized area within the field-of-view of the all-sky auroral imager operated at Syowa. Dome Fuji is located at the higher-latitude edge of the auroral zone, while Syowa is located in the middle of it. Auroral observations using the all-sky imager were also carried out at Dome Fuji in 2003. The simultaneous auroral and magnetic observations both at Dome Fuji and Syowa enabled us to study auroral activities in a larger area. This paper describes, the deployment and performance of the unmanned magnetometers in the JARE-44. One auroral substorm event is analyzed in detail to show the usefulness the unmanned magnetometer network.     

Gravity measurements with a portable absolute gravimeter A10 in Syowa Station and Langhovde,East Antarctica

Absolute gravity values were measured with a portable absolute gravimeter A10 in East Antarctica, for the first time by the Japanese Antarctic Research Expedition. This study aims to investigate regional spatiotemporal variations of ice mass distributions and associated crustal deformations around Syowa Station by means of repeated absolute gravity measurements, and we obtained the first absolute gravity value in Southern Langhovde on the Antarctic Continent. The average absolute gravity value at the newly installed benchmark AGS01 in Langhovde (obtained on 3 February 2012) was 982535584.2 ± 0.7 μgal (1 [μgal] = 1 × 10^?8 [m/s²]), which was in agreement with the gravity values obtained by the past relative gravity measurements within 1 mgal. In addition, the average absolute gravity value obtained at AGSaux in Syowa Station was consistent with both previous absolute gravity values and those obtained by simultaneous measurements using an FG5 gravimeter, owing to adequate data corrections associated with tidal effects and time variations in atomic clock frequencies. In order to detect the gravity changes associated with the ice mass changes and other tectonic phenomena, we plan to conduct absolute gravity measurements at AGS01 again and at other campaign sites around Syowa Station as well in the near future, with careful attention paid to the impacts of severe environmental conditions in Antarctica on gravity data collection.     

东南极内陆地区和乌鲁木齐河源1号冰川表层雪内NO^—3沉积后过程差异

酸性气体成分（如ＮＯ－３）的强挥发性导致其在雪面沉降后,具有沉积后气／雪交换作用,即其在表层雪内是“可逆”沉降的。通过比较东南极内陆雪坑的ＮＯ－３剖面和乌鲁木齐河源１号冰川表层雪内ＮＯ－３的浓度变化,认为沉积后气／雪交换作用在东南极内陆较显著,而在乌鲁木齐河源１号冰川则不然。表层雪内ＮＯ－３存在方式的不同和沉降机制的差异应是导致两地ＮＯ－３沉积后过程差异的原因所在。     

Extracting fair-weather data from atmospheric electric-field observations at Syowa Station, Antarctica

At Syowa Station (69.0°S, 39.6°E), located on East Ongul Island near the continent of Antarctica, atmospheric electric-field observations started in 1968 and had been carried out intermittently. An improved electric-field mill at Syowa Station had and obtained better-quality atmospheric electric-field data from February 2005 to January 2006. After a 1-year interruption, the observations resumed in January 2007.The atmospheric electric-field data from Syowa Station are often contaminated due to local disturbances caused by near-ground meteorological phenomena. We examined correlations between the atmospheric electric field and near-ground weather from February 2005 to January 2006 and from February 2007 to January 2008, and proposed a criterion to extract “fair-weather” electric-field data based on wind speed and cloud coverage data. The diurnal variation of fair-weather data in January followed the shape of the so-called Carnegie curve. Fair-weather data obtained during a substorm showed some correspondence between the atmospheric electric field and variations in the geomagnetic field. This newly developed extraction method may enable the use of atmospheric electric-field data for studying the solar terrestrial environment.     

Trends in cloud amount and radiative fluxes at Syowa Station,Antarctica

Variations of cloud amount and radiative fluxes are a matter of discussion related to the recent climate change in the Arctic and Antarctic. It is also of great concern related to “from dimming to brightening” recently found. Discussions based on satellite data had been conducted; however, no solid results are obtained from the surface station data for a long term in the recent.At Syowa Station, Antarctica, meteorological observation has been continued for nearly 50 years. During this term, an annual mean cloud amount showed a gradual increase at a rate of 0.014/yr. Radiation budget was observed since 1991 as one of the BSRN stations. Trends of monthly mean radiative fluxes were compared with those of cloud amount and conformable relations were seen during the period from 1991 to 2004. A cloud radiative forcing was estimated. In December, a downward trend in net longwave and net total appeared, while an upward trend in net shortwave was seen, and all corresponded to the decrease of cloud amount in this month. On the other hand in June, an upward trend in net longwave forcing was seen, corresponding to the increase of cloud amount. On an average, cloud radiative forcings at Syowa Station represented those of Antarctic costal stations near sea ice area.     

Propagation characteristics of the Pc3 frequency range pulsations in the cusp latitudes

Two induction magnetometers have been installed at Zhongshan Station and Davis Station, Antarctica respectively. We adopt with cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September,December 1996 and March 1997. to investigate the Pc3 frequency range pulsation occurrence and propagation characteristics in the cusp latitudes. The results are summarized as following:At Zhongshan-Davis Stations, the Pc3 frequency range pulsations occur mainly around the local noon/ local magnetic noon and local magnetic midnight respectively. In daytime, the pulsations have a seasonal variation in amplitude, occurrence and temporal range, all of them are sma1lest in winter. But in nighttime, the pulsations have no such a variation. The pu1sation amplitude in nighttime is much larger than the one in daytime all oveI the year. The pulsation propagating direction is mainly western in daytime and irregularly in nighttime. It can be thought that the different sources of the pulsation and the ionospheric electric conductivity are mainly responsible for these characteristics.     

Resting cells of microorganisms in the 20–100 μm fraction of marine sediments in an Antarctic coastal area

We investigated the morphological features, vertical sinking fluxes, and number densities of the resting cells of ice-associated microorganisms in the 20–100 μm fraction of natural marine sediments collected from ice-covered and ice-free areas around Syowa Station, Lützow-Holm Bay, East Antarctica. We identified the resting cells of various taxonomic groups, including the spores of a diatom, cysts of three dinoflagellates, cysts of five oligotrich ciliates, and the eggs of a mesozooplankton. This is the first report of oligotrich ciliate cysts from Antarctic waters. The resting spores of Thalassiosira australis (diatom), cysts of Polarella glacialis (dinoflagellate), and egg type 1 sink to the bottom sediment during summer. Our results suggest that some planktonic and ice-associated microorganisms in Antarctic coastal areas send their resting cells to the bottom sediments as seed populations for the following generation.     

极隙区Pc3频段脉动的传播特性

南极中山站和戴维斯站 (不变磁纬 74.5°S)白天中午位于磁层极隙区 ,夜间位于极盖区或极光带的极向边沿。两站均安装了完全相同的感应式磁力计。选择两站 1 997年 3月和 1 996年 6、9、1 2月的数据 ,运用快速傅立叶变换和波形检查方法选择 Pc3频段脉动事件 ,然后用信号互谱技术进行统计分析 ,结果如下 :在中山站 -戴维斯站 ,Pc3频段脉动主要出现于白天中午 /磁中午和磁午夜附近 ;白天 ,Pc3频段脉动振幅、出现率和出现的时间范围均有一定的季节变化 ,冬季最小 ,但在夜间 ,Pc3频段脉动没有这种变化 ;夜间 ,Pc3频段脉动振幅比在白天大许多 ;Pc3频段脉动传播方向 ,白天主要向西 ,夜间不太规则。这些可能反映了电离层电导率和日侧电离层电流系统对 Pc3频段脉动的影响。     

东南极普里兹湾海冰面地磁考察

中国第九次南极考察期间在中山站北部普里兹湾中面积约１３２ｋｍ２的测区内进行了地磁测量，为日后的南极内陆考察作前期准备。磁测资料表明，这里有一个宽约５－８ｋｍ、走向ＮＷ的磁异常，其幅度达５００ｎＴ。磁异常可能是由深成岩浆的侵入体或富含磁铁矿的地质体引起的，磁源物体的埋深在海冰面以下０．３－２．０ｋｍ。考察实践证明：只要经过充分准备，利用普里兹湾冬季冰封的有利条件，开展大范围的海冰面地球物理考察，在技术上是可行的。     

南极中山站地磁脉动的观测分析

本文分析的是１９９２年２月９日至１９９３年２月９日在南极中山站记录的各种地磁脉动的观测资料，并对各种地磁脉动的激发机制进行了初步讨论。通过南极中山站地磁脉动观测资料分析，了解高纬地区地磁脉动的形态特征，对南极极隙区高空大气电磁环境、太阳风和磁层相互作用等现象有进一步的认识。     

南极地区Es特性研究

Es是发生在电离层E层高度上的偶发电离增强结构,其电子密度最高可达E层背景电子密度的100倍以上。Es出现概率和强度全球分布不均,主要分布在中低纬度地区,极区也有较强Es出现并具有显著特点,极区Es的研究,对研究Es成因和物理机理具有重要科学意义。本文利用Syowa站（69.0°S,39.6°E）40余年的观测数据,选取临界频率和虚高两个参数,研究了南极地区Es强度特性、日变化、季节变化及长期变化特性。     

南极中山站的f_0F2特征

本文利用电离层数字测高仪 (DPS - 4)所测的f0 F2和从美国NOAA和DMSP卫星观测估算的半球功率指数和午夜极光区赤道侧边界纬度等资料 ,考察中山站电离层的极区特征。结果表明 ,冬季中山站电离层内的电离生成主要取决于从磁层沉降的粒子。在太阳活动和地磁变化宁静环境下 ,磁正午极隙区内的软粒子是最主要的电离源 ,它能使f0 F2达全天的最大值 ;上、下午各有数小时处于极光带内时 ,高能粒子的电离作用也很重要 ;夜间进入极盖区后 ,电子密度则很低。夏季太阳辐射电离效应使f0 F2值比冬季增加 1- 1 .5MHz,而其日变化的最大值时间也提前了 1- 2hr。发生很大扰动时 ,极隙区和极光带的位置均向低纬方向移动。若中山站日间也处于极盖区内时 ,电子密度会大幅度下降 ,并常接收不到电离层回波的信号。在中等扰动环境下情况更加复杂。由于高纬电离层对流速度很高 ,离子 /中性分子间的碰撞复合系数就很大。热层中性大气全球经向环流对高纬电离层电子密度的增加无显著作用。磁暴期间中午从极隙区向南的等离子体对流对中山站f0 F2的增高也无明显影响。     

南极极夜期间臭氧含量变化及其与平流层风温关系

本文利用昭和基地 (6 9°0 0′ S,3 9°3 5′ E) 1 982～ 1 987年的臭氧总量的探空资料 ,着重分析了1 987年南极昭和站极夜期间臭氧含量变化与 5 0 h Pa风速、气温及变温的关系。发现在极夜期间 ,臭氧含量与 5 0 h Pa风速存在较好的相关性。根据热成风原理 ,计算了极夜期间的温度平流项 ,发现臭氧含量与 5 0 h Pa温度平流也存在一定的相关性 ,变温 ΔT的变化主要是由温度平流引起的。平流层臭氧只具有微弱的加热效应     

Statistics of Antarctic surface meteorology based on hourly data in 1957–2007 at Syowa Station

Statistical characteristics of the surface meteorology are examined at Syowa Station (69°00′S, 39°35′E), which is located on an island near the coastal region of the Antarctic continent, based on operational observations made over the 50-year period from February 1957 through January 2007, which includes missing periods equivalent to 5 years. Statistics are obtained for the surface temperature, sea level pressure (SLP), and horizontal winds in terms of frequency distribution, frequency power spectra, seasonal variation, diurnal variation, inter-annual variation, and trends, using hourly observation data, and several interesting characteristics are elucidated. The mean temperature, SLP, and wind speed over the 50-year period are −10.5 °C, 986 hPa, and 6.6 m s⁻¹, respectively. The frequency distribution of temperature is far from the normal one, because less variation exists in summer at higher temperatures. The predominant wind direction is northeasterly (southwestward), and a weak secondary peak is observed in the southerly (northward) direction in the frequency distribution. The directional constancy of winds is 0.78. The frequency spectra over a wide range of 2 h to 20 years exhibit clearly isolated peaks corresponding to annual and diurnal frequencies and their higher harmonics. An important finding is that the spectral shape is proportional to a power of the frequency with a transition frequency for all physical parameters. The transition frequencies correspond to about 5 days for temperature and winds and 3 days for SLP, most likely due to cyclonic activity. A peak in the 11-year solar cycle is not identified in any spectrum. Another interesting feature is the dominance of semi-annual and semi-diurnal variations in SLP, while annual and diurnal variations are dominant for temperature and winds. Statistically significant trends are not detected for annual mean surface temperature and SLP over the 50-year period, while a positive trend is significant for wind speed. These trends are also examined as a function of the months. The inter-annual variation of SLP is well correlated with that of the Antarctic Oscillation index, indicating that Syowa Station can be regarded as a typical Antarctic station. Furthermore, statistical analysis was conducted for blizzards (severe snow storms), in terms of duration, and seasonal and inter-annual variation in frequency of occurrence. It is shown that the blizzards are dominant in the period from late March to late October. No systematic variation in blizzard frequency was observed during the 50-year period. Instead, the frequency depends largely on the year with a minimum of nine in 1988 and a maximum of 42 in 1982. As a typical example, a synoptic chart is used to show the cause of a strong snow storm on 27 May 1996, when the absolute maximum gust was observed.     

The capabilities of the EISCAT Svalbard Radar for inter-hemispheric coordinated studies

In this article we want to present the EISCAT Svalbard Radar (ESR) in some detail, as well as some of the instruments of interest for ionospheric and magnetospheric research that are located in the vicinity of it. We particularly describe how this instrument cluster, close to the geomagnetic conjugate point of the Chinese Antarctic Zhongshan Station, can contribute to inter hemispheric coordinated studies of the polar ionosphere.     

Propagation and source of Pc5 frequency range pulsation at cusp latitude

Two induction magnetometers have been installed at Chinese Zhongshan Station and Australia Davis Station, Antarctica respectively. We adopt the cross spectral analysis technique to analyze the data of the two induction magnetometers, in June, September, December 1996 and March 1997, and to investigate Pc5 frequency range pulsation (150 600 s) occurrence and propagation in cusp latitude. The results are summarized as follows: At Zhongshan Davis Station, the magnetic pulsations in Pc5 frequency band can occurs over a wide time, but more frequently at pre local magnetic noon and pre local magnetic midnight. The Pc5 pulsations have no significant seasonal variation in the amplitude, occurrence and propagation. The amplitude has a small peak at pre local magnetic noon and large value sometimes at pre local magnetic midnight. In daytime, the Pc5 pulsations propagate westward in morning and eastward in afternoon, and reversal at local magnetic noon. In nighttime, the Pc5 pulsations propagate westward before 20:00 MLT and eastward after 20:00 MLT. Near dusk time, the Pc5 pulsations propagate irregularly. These characteristics indicate that the Pc5 pulsations have different source at different local magnetic time.     

CHARACTERISTICS OF Sq VARIATION OF GEOMAGNETIC FIELD AT THE GREAT WALL STATION, ANTARCTICA IN WINTER

In this paper the characteristics of Sq variation of geomagnetic field in the region of the Chinese Great Wall Station (CGWS), Antarctica, in winter are analyzed from geomagnetic data obtained at the Geomagnetic Observatory of CGWS. The result enables us to reveal the following aspects: (1) The pattern of Sq variation at CGWS in early (Apr.) and Late winter (Sep.) is similar to that at Beijing Geomagnetic Observatory (BJO) at the middle latitude in the Northern Hemisphere. It may be controlled by the midlatitudinal ionospheric dynamo current. Amplitude of Sq variation is very small, and the harmonics in 8 hours or shorter periods in midwinter (June and July) is predominant because of the decreased effect of solar ultraviolet radiation and the dominant geomagnetic disturbance at high latitudes. (2) The vectors of Sq-equivalent current in the daytime are about five times more than that in the night. The direction of the vectors is clockwise in the daytime (08-15h) and counterclockwise in the night in earl     

南极臭氧洞期间中山站和昭和站大气臭氧的中期振荡特征

本文用１９９３和１９９４年７～１２月中山站及昭和站大气臭氧观测资料和１９９３年７～１２月中山站地面温度、气压及戴维斯站探空资料，对南极臭氧洞期间中山站和昭和站的中期振荡特征进行了研究。结果表明：准一周和准二周振荡是南极地区大气臭氧和各层次温压参数普遍存在的两种主振荡周期，且在不同年份其振荡强度也有所不同。在中山站和昭和站地区，１９９３年大气各参数的准二周振荡强度大于准一周振荡，准一周和准二周振荡都是由西向东传播的；而在１９９４年则除准一周振荡外未出现准二周振荡。在普里兹湾地区平流层中下部臭氧和等压面高度、温度准一周和准二周振荡的位相差很小，振荡是同时发生的。准一周和准二周振荡都可以由上而下或由下而上地穿越对流层顶，平流层和对流层的中期振荡有着密切的关系。准二周振荡是大气中普遍存在的一种天气尺度的中期振荡，在不同地区可以对应不同的天气实体。在南极地区，大气臭氧总量的准二周振荡可能是极涡本身固有振荡的反映，而周期较短的准一周振荡则可能是外来扰动强迫振荡的反映。     

Summer weather characteristics on the Grove Mountain of East Antarctica

The summer weather characteristics of the Grove Mountain, East Antarctica, are presented based on the data obtained by Chinese National Antarctic Expedition (CHINARE) in January 1999. The result shows that the pattern of daily variation of temperature and the prevailing wind direction in Grove is similar to that of Zhongshan Station. However, the daily range of temperature and strong wind frequency are much higher than those of Zhongshan Station.The change of wind direction is close to the weather system that impacted the Grove Mountain. The warm and wet air from northern parts often causes the precipitation. The clear weather appears when controlled by eastern winds in January.     

Localization of VLF ionospheric exit point by comparison of multipoint ground-based observation with full-wave analysis

In order to estimate the dynamic structure of the VLF ionospheric exit point, we conducted multipoint ground-based observation of the natural VLF emissions at three unmanned sites: West Ongul (69°01′ S, 39°30′ E), Skallen (69°40′ S, 39°24′ E), and H100 (69°18′ S, 41°19′ E) around Japanese Syowa station, Antarctica, during a whole year of 2006. In this observation, we developed three sets of unmanned autonomous observation systems for natural VLF emissions. Each observation system consists of two crossed vertical loop antennas to pick-up North–South (NS) and East–West (EW) magnetic components, a multi-channel analyzer, and a data logger. The intensity and polarization of NS and EW magnetic components are obtained in 4 spaced frequency (0.5, 1.0, 2.0, and 6.0 kHz) channels by the multi-channel analyzer.The VLF emissions observed at the three sites exhibit an interesting difference in the wave intensity as well as the polarization that allows important information about the locations of their ionospheric exit point to be determined. Firstly, to find the distinct exit point, we have theoretically calculated the spatial distributions of the wave intensity and the polarization on the Earth for VLF whistler mode waves coming down from the magnetized ionosphere, by using the full-wave analysis. Then, we have compared the calculated results with the observed data, to evaluate the possible locations of the ionospheric exit point for the auroral hiss events.As an example, the direction of the estimated ionospheric exit point for the auroral hiss event at 31 March 2006 was found to be consistent with a bright aurora region. However, in this case, the estimated ionospheric exit point was located a few hundred kilometers equatorward of the associated aurora. This would suggest that the ray paths for the auroral hiss could be different from the directions of the geomagnetic field lines for auroral precipitation.