林显浩,
陈薇,
王勇,
陆鹏,
龚文颖,
马文琛,
花漫,
刘阳希子
武汉大学电子信息学院空间物理系, 武汉 430072
基金项目: 国家自然科学基金(41904143)和中国博士后科学基金(2019M662700)资助
详细信息
作者简介: 项正, 男, 武汉大学空间物理系特聘副研究员, 主要从事辐射带动力学方面的研究.E-mail: xiangzheng@whu.edu.cn
中图分类号: P353 收稿日期:2021-02-24
修回日期:2021-04-17
上线日期:2021-11-10
Global morphology of NWC and NAA very-low-frequency transmitter signals in the inner magnetosphere: A survey using Van Allen Probes EMFISIS measurements
XIANG Zheng,LIN XianHao,
CHEN Wei,
WANG Yong,
LU Peng,
GONG WenYing,
MA WenChen,
HUA Man,
LIU YangXiZi
Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan 430072, China
MSC: P353
--> Received Date: 24 February 2021
Revised Date: 17 April 2021
Available Online: 10 November 2021
摘要
摘要:地球表面的人工甚低频台站信号可以穿透电离层泄漏进地球磁层导致内辐射带电子沉降到两极大气.因此研究人工甚低频台站信号的空间全球分布特性对于分析辐射带电子的损失具有重要科学意义.本文使用范阿伦双星从2013年到2018年共计6年的高质量的波动观测数据，统计了NWC(19.8 kHz)、NAA(24.0 kHz)两个人工VLF台站信号的全球分布，分析了台站信号的电场功率谱密度对地理经纬度、磁壳值L、磁地方时MLT、地磁活动水平的依赖性.结果表明，在内磁层中，人工台站VLF信号主要沿着台站位置对应的磁力线传播，夜侧强度高于日侧，冬季高于夏季.这种日夜和夏冬差异的形成是因为夜侧和冬季的日照强度较弱，电离层电子密度较低，VLF信号较容易穿透电离层进入磁层.此外人工VLF台站信号的全球分布受地磁活动的影响很弱.这些统计观测结果给出了NWC和NAA两个重要人工VLF台站信号强度的全球分布特征，为进一步分析人工VLF台站信号与地球辐射带电子的波粒相互作用提供了关键信息.
关键词: 人工甚低频台站信号/
范阿伦双星/
全球分布/
内磁层
Abstract:Signals from ground-based artificial VLF transmitters can penetrate through the ionosphere and leak into the Earth's magnetosphere, leading to inner radiation belt electrons precipitation into the atmosphere. It is of great scientific significance to study the global spatial distribution characteristics of VLF transmitter signals for analyzing the loss of radiation belt electrons. In this study, using 6 years high-quality wave measurements from Van Allen Probes during 2013-2018, we investigate the global distribution characteristics of NWC (19.8 kHz) and NAA (24.0 kHz) transmitter signals in detail, and systematically analyze the dependences of the transmitter signals distribution on the geographic latitude and longitude, L-shell, MLT, and geomagnetic activity level. The results suggest that the VLF transmitter signals in the inner magnetosphere mainly propagate along the magnetic field line across the station position. The averaged wave power intensities peak on the nightside of the Earth, and become more intensive in the winter months. The electron density is lower in the nightside and winter due to reduced sunlight, thus more wave powers leak into the magnetosphere. Meanwhile, the geomagnetic activities have slight influences on the global distributions of VLF transmitter signals. Based on these statistical observations, we obtain the global distribution characteristics of NWC and NAA transmitter signals intensities, which provide key information for further analysis of the wave-particles interactions between the VLF signals and radiation belt electrons.
Key words:Artificial very low frequency transmitter signals/
Van Allen Probes/
Global distributions/
Inner magnetosphere
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