Climatological features of electron density in the polar ionosphere from long-term observations of EISCAT/ESR radar
Climatological features of electron density in the polar ionosphere from long-term observations of EISCAT/ESR radar
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DOI：
10.5194/angeo-25-2561-2007
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发表时间：
2007-01
影响因子：
1.9
通讯作者：
H. Cai;Shuying Ma;Y. Fan;Yi Liu;K. Schlegel
中科院分区：
文献类型：
--
作者：
H. Cai;Shuying Ma;Y. Fan;Yi Liu;K. Schlegel
抽象的。本文利用欧洲非相干散射超高频雷达（EISCAT）和斯瓦尔巴特EISCAT雷达（ESR）的长期观测资料，通过统计分析，研究了极区F2区电子密度（Ne）的气候特征。EISCAT和ESR雷达在CP-1和CP-2模式下工作的场对准测量用于本研究，涵盖1988-1999年EISCAT和1999-2003年ESR。数据按季节（春分、夏季和冬季）和太阳周期阶段（最大、最小、上升和下降）排序。结果表明：（1）EISCAT的冬季异常在太阳活动峰期明显，但在ESR纬度消失;（2）EISCAT的Ne日间峰值在太阳活动峰期各季节比ESR日间峰值滞后1-2 h，高度比ESR低10-30 km。(3)除了白天的峰值外，在太阳活动极大期前后的ESR磁午夜前还有一个峰值，特别是在冬季和春分点。ESR观测到的磁中午附近的白天电离峰可以归因于尖点区域的软粒子降水，而午夜前的Ne最大值似乎与该时间段经常爆发的亚暴事件密切相关，特别是对于冬季的情况。(4)在太阳活动极小期和太阳活动周期下降期，EISCAT观测结果存在半年变化;但在太阳活动周期上升期，EISCAT观测结果没有表现出明显的季节变化。
Abstract. In this paper, climatological features of the polar F2-region electron density (Ne) are investigated by means of statistical analysis using long-term observations from the European Incoherent Scatter UHF radar (called EISCAT in the following) and the EISCAT Svalbard radar (ESR) during periods of quiet to moderate geomagnetic activity. Field-aligned measurements by the EISCAT and ESR radars operating in CP-1 and CP-2 modes are used in this study, covering the years 1988–1999 for EISCAT and 1999–2003 for ESR. The data are sorted by season (equinox, summer and winter) and solar cycle phase (maximum, minimum, rising and falling). Some novel and interesting results are presented as follows: (1) The well-known winter anomaly is evident during the solar maximum at EISCAT, but it dies out at the latitude of the ESR; (2) The daytime peaks of Ne at EISCAT for all seasons during solar maximum lag about 1–2 h behind those at ESR, with altitudes about 10–30 km lower. (3) In addition to the daytime peak, it is revealed that there is another peak just before magnetic midnight at ESR around solar maximum, especially in winter and at equinox. The day-time ionization peak around magnetic noon observed by ESR can be attributed to soft particle precipitation in the cusp region, whereas the pre-midnight Ne maximum seems likely to be closely related to substorm events which frequently break out during that time sector, in particular for the winter case. (4) Semiannual variations are found at EISCAT during solar minimum and the falling phase of the solar cycle; at the rising phase, however, the EISCAT observations show no obvious seasonal variations.