南极SIPLE导管哨声模信号传播路径分析和出现特性

南极SIPLE导管哨声模信号传播路径分析和出现特性 PATH ANALYSES AND OCCURRENCE PROPERTIES OF DUCTED WHISTLER-MODE SIGNALS FROM SIPLE, ANTARCTICA 保宗悌 Bao Zongti first-author D.L.Carpenter 本文报导了对在南极Siple站（75.940°S,84.248°W）新设大功率甚低频发射机所发射的导管哨声模信号传播路经和出现特性的研究,着重研究传播路径与出现特性对发射功率和频率的依赖关系。新设的Jupiter发射机比1979年以前用的Zeus发射机在功率方面约大7分贝,在2—4千赫频段的Siple信号的检测百分率有明显的增加,传播路径比以往更加集中在以Siple站为中心、南北向±150公里,高度为100公里的范围内。最典型的路径磁旋频率为9.2千赫。在这条路径中,传播信号与飘移的低能电子相互作用,信号频率愈低对应的谐振能量愈大.在1980年5月—8月Siple信号活动最强的期间,日变化曲线有明显的夜间最小值和黎明最大值。还新发现有第二个信号活动最大值,出现在当地时间19MLT左右。同时,从1980年—1981年南极夏季有限的观测发现在当时中午时间有集中的信号活动。此外,还对南极冬季和南极夏季的信号活动加以比较,发现活动的持续时间与季节有明显的关系,而且与甚低频发射同时发生、同时消失。这种相关在发射频率为2—4千赫时最明显。 Occurrence features of an extensive data set acquired in 1980 were studied, and propagation-path analyses were performed for 21 periods from 12 days in the austral winter of 1980. Optimum frequencies for VLF transmitting experiments have been found to lie below 4 KHz, in spite of limitations on radiated power in that range imposed by antenna cfficiency. Comparisons were made between results from the more powerful（～7 dB） Jupiter transmitter in 1980 and from the prcvious system, Zeus, in 1978. Jupiter achieved a roughly factor of two improvement over Zeus in the percentage of detected signals in the 2-4 KHz band. A major part of this improvement was below 3 KHz, where Jupiter produced a radiated signal of ～175 w, while Zeus produced ～25 W. In the May-August 1980 diurnal activity records, the previously noted nightside minimum and dawn maximum were well defined. A secondary activity peak near 19 MLT may be due to the destabilization of longitudinally drifting low energy electrons as they penetrate the dusk-side plasmasphere bulge. The limited data base for the 1980-81 austral summer shows a concentration of transmitter signal activity near local noon, which may be due to the formation of a secondary plasmasphere bulge by quiet-day drifts near noon and the penetration of this bulge by drifting low energy electrons. A strong seasonal variation in duration of detected signal activity was observed. The longest period of the day regularly exceeded two hours in length the 1980 austral winter, but rarely exceeded one hour in the summer. In the path analyses the stronger Siple paths were found to be in the range 4<L<4.75, a range centered approximately overhead at Siple/Roberval at 100 km altitude. 武大空间物理系保宗悌教授于1980—1982年应邀赴美国Stanford大学与D.L.Carpenter教授合作研究项目 1983-04-01 2021-04-01 4