基于Van Allen Probes EMFISIS波动仪器观测的内磁层上频带哨声合声波全球分布的统计分析  

A statistical analysis of the global distribution of inner magnetospheric upper-band chorus waves based on Van Allen Probes EMFISIS observations

作　　者：顾旭东[1] 殷倩[1] 周若贤 易娟[1] 倪彬彬[1] 项正 曹兴[1] 邹正洋 付松[1] 周晨[1] 石润[1] 赵正予[1] 贺丰明 谈家强 郑程耀 王豪[1] 

机构地区：[1]武汉大学电子信息学院空间物理系,武汉430072

出　　处：《地球物理学报》2017年第4期1259-1267,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41204120;41304130;41474141;41574160);中国博士后科学基金(2013M542041;2014T70732;2015M582265);国家级大学生创新创业项目(201510486081)联合资助

摘　　要：基于Van Allen Probes近三年的EMFISIS仪器波动观测数据,针对内磁层上频带哨声模合声波幅度的全球分布特性对地磁活动水平的依赖性进行了详细的统计分析,着重研究上频带合声波平均场强幅度随磁壳值(L)、磁地方时(MLT)、地磁纬度(MLAT)的分布特征及不同强度区间的合声波的发生概率.结果表明,上频带合声波的平均场强幅度与地磁活动条件密切相关,在强磁扰期,平均幅度可达到40 pT以上.在外辐射带中心区域(L=4~6),上频带合声波的幅度最强;在L<~3的区域,上频带磁层合声波没有分布.在夜侧至晨侧(22—09MLT),上频带合声波幅度最强;在下午侧至昏侧(15-19MLT),上频带合声波幅度最弱;日侧(10-14MLT)上频带合声波在不同地磁活动条件下都存在,幅度偏小.上频带合声波主要分布在|MLAT|<10°,其中21-09MLT范围内、磁纬位于|MLAT丨<5°的平均场强幅度最强,磁扰期间可达约100 pT.另外,统计而言,中等幅度(10~30 pT)的上频带合声波在夜侧至晨侧(23-09MLT)靠近磁赤道区域的发生率最高,可达15%左右.强幅度(>30 pT)的上频带合声波普遍分布在夜侧(01-05MLT),发生率最小.本文建立的上频带哨声模合声波的全球分布模型结合已经建立的下频带合声波的全球分布模型,将有助于进一步深入理解该重要磁层等离子体波动对地球等离子体片、辐射带、环电流动力学过程的定量贡献.Based on the nearly three-year wave data from the EMFISIS instrument onboard the Van Allen Probes, a statistical analysis of the global distribution of inner magnetospheric upper-band chorus is performed in detail with respect to the level of geomagnetic activity. The emphasis is placed upon the quantitative variations of average upper-band chorus wave amplitude with L-shell （L）, magnetic local time （MLT） and magnetic latitude （MLAT） and the occurrence pattern of upper-band chorus waves at different amplitude levels. The results indicate that there exists a strong positive correlation between the average wave amplitude and the geomagnetic activity level, and the averaged wave amplitude can be larger than 40 pT during geomagnetically active periods. While wave amplitude reaches the maximum in the central region （L=4~6） of outer radiation belt, upper-band chorus cannot be observed at L〈~3.Averaged wave amplitude is found to be strongest during the interval from nightside to dawnside and is weakest during the interval from afternoonside to duskside. Dayside upper-band chorus can be observed at different geomagnetical conditions with relatively small wave amplitude. It is found that upper-band chorus is mainly distributed at ｜MLAT｜〈10°. Averaged wave amplitude is strongest in the region of 21-09 MLT and ｜MLAT｜〈5°, and can be about 100 pT during geomagnetically active periods. In addition, the occurrence rate of moderate amplitude （10~30 pT） upper-band chorus is statistically found to be highest （~15%） near the equatorial region in the MLT sector from nightside to dawnside （23-09 MLT）.Upper-band chorus with strong wave amplitude has the lowest occurrence rate and is generally observed at the nightside （01-05 MLT）. Combined with the global distribution and occurrence pattern of lower-band chorus we have already established, the global distribution and occurrence pattern of upper-band chorus established in this study will improve the understanding of the quantitative contr

关 键 词：上频带合声波 内磁层 统计分析 平均场强 发生率 

分 类 号：P353[天文地球—空间物理学]