Statistical analysis of plasmaspheric plumes with Cluster/WHISPER observations
Statistical analysis of plasmaspheric plumes with Cluster/WHISPER observations
复制标题
DOI：
10.5194/angeo-26-2403-2008
复制
发表时间：
2008-08
影响因子：
1.9
通讯作者：
F. Darrouzet;J. Keyser;P. Décréau;F. Mazouz;X. Vallières
中科院分区：
文献类型：
--
作者：
F. Darrouzet;J. Keyser;P. Décréau;F. Mazouz;X. Vallières
等离子体层羽流已经被四个星团航天器定期观测到。本文介绍了一个统计分析的羽流观测五年（从2001年2月1日至2006年2月1日）的基础上四点测量的等离子体辐射（4个地球半径以外），因为它是由航天器在一个狭窄的本地时间扇区之前和之后的近地点采样。等离子体层羽流可以从电子密度分布图中识别出来，电子密度分布图是由星团上的WHISPER波探测器确定的电子等离子体频率得出的。由于WHISPER仪器的频率范围有限（2-80 kHz），因此只能识别密度低于80 cm 3的羽流。研究了它们的产状与几个地磁指标（Kp、am和Dst）的关系.讨论了它们的横赤道尺寸、磁地方时分布、L位置和密度变化。等离子体层羽流观察大多为中等Kp，从来没有小DST。它们主要出现在下午和午夜前的MLT部门。还比较了近地点交叉前后的羽流在轨道内和外段交叉时的密度分布。
Plasmaspheric plumes have been routinely ob- served by the four Cluster spacecraft. This paper presents a statistical analysis of plumes observed during five years (from 1 February 2001 to 1 February 2006) based on four- point measurements of the plasmasphere (outside 4 Earth radii) as it is sampled by the spacecraft in a narrow local time sector before and after perigee. Plasmaspheric plumes can be identified from electron density profiles derived from the electron plasma frequency determined by the WHISPER wave sounder onboard Cluster. As the WHISPER instru- ment has a limited frequency range (2-80 kHz) only plumes with densities below 80 cm 3 can be identified in this way. Their occurrence is studied as a function of several geomag- netic indices (Kp, am and Dst ). Their transverse equatorial size, magnetic local time distribution, L position and density variation are discussed. Plasmaspheric plumes are observed mostly for moderate Kp and never for small Dst . They are found mainly in the afternoon and pre-midnight MLT sectors. Comparisons are also made between the density profiles of the plumes as they are crossed on the in- and outbound legs of the orbit, before and after perigee crossing, respectively.