日侧极光卵的可见光多波段观测特征——中国北极黄河站首次极光观测初步分析

中国在斯瓦尔巴特(Svalbard)群岛新奥尔松(Ny-Alesund)地区建立了一个永久性科学考察站--北极黄河站。北极黄河站(78．92°N,11．93 °E)的修正磁纬为76．24°。2003年11月黄河站建立了一套多波段(427．8nm,557．7nm,630．0nm)单色极光全天空CCD成像观测系统,并于2003年12月11日-2004年2月25日极夜期开展了首次极光越冬观测,获得了1200多小时的连续观测数据。利用这1200多小时观测数据制作了以时间为横轴的南北向极光活动图,对日侧极光卵的极光活动特征进行了研究。初步分析发现,沿日侧极光卵不论磁静日还是磁扰日,在三个波段上都同时观测到了四个重复出现的极光活动区,即0900MLT(磁地方时)附近的 A区、1330MLT的B区和1630MLT的C区以及1200MLT附近的G区。A区内的极光活动由低纬向高纬运动,强度逐渐变弱,形态由较宽的弧状极光向冕状极光演变;B区内的极光活动由高纬向低纬方向运动,形态呈现为冕状极光向较窄的极光弧的演变,极光强度逐渐增强;C区极光活动向高纬方向展宽,强度逐渐变弱,极光由单弧向多重弧演化;而在A与B之间存在一个纬度范围相对较窄的极光活动区G区,该区的极光呈现暗弱的冕状极光。日侧极光活动随时间从午前、正午到午后呈现出一个系统的光谱变化:绿色-红色-绿色。A区的位置出现在卫星探测的午前极光峰之中;而正午附近极光强度暗弱的G区,可部分地解释卫星观测的所谓“正午极光空白区”;卫星观测到的1500MLT附近的“极光热点”区在地面观测中可以区分为以红色极光为主的B区和以绿色极光为主的C区。

MULTIPLE WAVELENGTHS OBSERVATION OF DAYSIDE AURORAS IN VISIBLE RANGE--A Preliminary Result of the First Wintering Aurora Observation in Chinese Arctic Station at Ny-(A)lesund

China has established its first Arctic station, named Yellow River Station, in Ny-Alesund, Svalbard from Oct. 2003. A multiple wavelength monochromatic all-sky CCD imagers system has been deployed in this station, which monitors aurora phenomena on 427. 8nm,557. 7nm and 630. Onm. Wintering observation with the all-sky imagers system was carried out from Dec. 11th, 2003 to Feb. 25th, 2004, and about 1200 hours of aurora image data was collected. All those all-sky images were processed into keograms along the magnetic North-South direction o-ver time in UT. Multiple wavelengths characteristics of dayside aurora activities were investigated with these keograms and in reference to all-sky images. It was found that there are three repeatedly appearing aurora activity regions along the dayside aurora oval. They are, Region A a-round 0900MLT in which aurora moves poleward while its intensity decreasing, and its form changing from arc to corona widi time; Region B around 1330MLT in which aurora moves equa-torward while its intensity increasing, and its form changing from corona to arc in time; Region C around 1330MLT in which aurora expands poleward while its intensity decreasing, and its forma evolving from arc to multiple arcs in time. There is a narrow belt of aurora activity in North-South direction between Regions A and B, which is dominated by weak and red corona aurora. From morning to noon and evening, the dominating color of dayside aurora displays a systematic changing pattern as Green-Red-Green. The Region A aurora activity in this study coincides temporally with the prenoon aurora peak, while Region B together with Region C correspondent to the 15MLT "Hot Spot" in satellite observations. The features of narrow latitude range and weak intensity found with the aurora belt G around MLT noon could account for why it appeared as a "Midday Gap" in satellite observations. Interesting result of this study is that "Hot Spot" could be further divided into two activity regions with different characteristics.