Statistical study of the distribution properties of very-low-frequency transmitter signals based on CSES wave measurements
-
摘要:
地基人工甚低频(10~30 kHz)台站信号可以穿透电离层, 甚至泄露进地球磁层, 从而导致内辐射带高能电子的沉降.研究人工甚低频台站信号的特征对于研究辐射带电子的损失具有重要的科学意义.基于张衡一号卫星2019—2022年的电场观测数据, 本文对全球10个人工甚低频台站在电离层中的信号特征进行了研究, 统计分析了电离层中人工甚低频台站信号的昼夜差异、季变规律、对地磁活动水平的依赖性, 及其在地磁共轭区的分布特征.结果表明, 人工甚低频台站信号会传播至台站上空电离层及其共轭区, 信号辐射范围及强度与台站的发射功率呈正相关.电离层电子密度对甚低频信号的传播具有重要影响, 在夜侧和当地冬季, 电离层电子密度相对较小时, 泄露进入内磁层的人工甚低频台站信号较强, 而信号强度受地磁活动影响很弱.在台站上空, 信号增强区域以穿刺点为中心呈现近圆形分布, 并存在明显的波模干涉效应, 在共轭半球, 信号增强区域中心相对共轭穿刺点会发生极向漂移(L＜2的台站)或赤道向漂移(L＞2的台站), 但所有台站的电波能量都被限制在1/2赤道电子回旋频率磁壳以内的区域.这些统计观测特征表明, 发射台站位于较低L值(L＜1.4)的人工甚低频台站信号在内磁层中主要以非导管模式传播到共轭半球, 而发射台站位于较高L值(L＞2.6)的人工甚低频台站信号主要以导管模式传播.
Abstract:Very-Low-Frequency (VLF) signals from ground-based transmitters could penetrate through the ionosphere, and even leak into the Earth's magnetosphere, leading to the precipitation of inner radiation belt electron. Therefore, detailed information about the distribution characteristics of VLF transmitter signals in geo-space is of great importance for in-depth understanding of their driven radiation belt electron loss processes and consequences. Using the electric field measurements from the China Seismo-Electromagnetic Satellite (CSES) during the period from 2019 to 2022, we distinguish the VLF signals in the ionosphere emitted from 10 ground-based transmitters, and statistically investigate their diurnal differences, seasonal variations, geomagnetic activity dependence, and distribution characteristics at the geomagnetic conjugate region. The results indicate that, in terms of propagating into the ionosphere and its conjugate region, the VLF transmitter signals have their radiation radii and amplitudes positively correlated with the transmitted powers of the corresponding stations. The ionosphere electron density has a significant effect on the propagation of VLF transmitter signals. On the night-side and during the months of local winter, the ionosphere electron density is relatively smaller, leading to stronger VLF transmitter signals in the ionosphere. In contrast, the amplitudes of these signals are weakly affected by the level of geomagnetic activity. At the overhead region of the VLF transmitter stations, the radiation patterns show a nearly circular distribution centered on the puncture point, and there are obvious wave mode interference effect. However, at the conjugate region, the center of the enhancement area has the tendency of polar drift (for the stations with L < 2) or equatorial drift (for the stations with L > 2) relative to the conjugate puncture point. Furthermore, the VLF transmitter signals for all stations are very likely confined to the regions within the 1/2 equatorial electron cyclotron frequency of the specific magnetic shell. These features strongly support the hypothesis that VLF transmitter signals prefer to propagate to the conjugate hemisphere in the non-ducted mode when the transmitter is located at lower L shells (L < 1.4) but in the ducted mode at higher L shells (L > 2.6).
-
-
图 1
夜侧人工甚低频台站上空总电场功率谱密度平面图及其随时间的变化曲线
Figure 1.
The averaged radiation pattern and time series curve of total electric field power spectral density from the VLF transmitters, as detected by CSES on the night-side
图 2
日侧人工甚低频台站上空总电场功率谱密度平面图及其随时间的变化曲线
Figure 2.
The averaged radiation pattern and time series curve of total electric field power spectral density from the VLF transmitters, as detected by CSES on the dayside
图 3
人工甚低频台站信号总电场功率谱密度随AE指数的变化曲线
Figure 3.
The variation with geomagnetic index AE of the electric field power spectral density of the VLF transmitters
图 4
人工甚低频台站及其共轭区上空总电场功率谱平面图
Figure 4.
The electric field radiation pattern from the VLF transmitters at both the overhead and geomagnetic conjugate region
图 5
NWC甚低频台站上空不同卫星观测的电场功率谱密度随纬度的变化曲线
Figure 5.
The electric power spectral density curve observed by three different satellites at the overhead region of NWC transmitter
表 1
本文研究的人工甚低频台站列表
Table 1.
VLF transmitter stations studied in this paper
台站名称 地理经度/(°E) 地理纬度/(°N) L值 频率/kHz 功率/kW NPM -158.15 21.42 1.17 21.4 600①② JJI 130.83 32.09 1.24 22.2 100① NWC 114.17 -21.82 1.43 19.8 1000①② ICV 9.73 40.92 1.51 20.3 50① FTA2 2.58 48.54 1.95 20.9 约50① DHO38 7.61 53.08 2.39 23.4 300①/500② GQD -3.28 54.91 2.66 19.6 100①/500② NAA -67.28 44.65 2.86 24 1000①② NLK -121.92 48.20 2.89 24.8 250①② NML -98.33 46.37 3.26 25.2 250①/500② 注：①引自Meredith等(2019)；②引自Zhang等(2018). 
下载: 导出CSV
表 2
人工甚低频台站信号的辐射半径及总电场功率谱密度统计结果
Table 2.
The statistical result of radiation radius and total electric field power spectral density for the VLF transmitters
台站名称 信号辐射半径/km 总电场功率谱密度中位值/log(mV·m-1·Hz-1) 夜侧 日侧 夜侧 日侧 NPM 800 — [-2.51, -1.31] [-4.02, -2.57] JJI 800 — [-2.31, -1.46] [-4.45, -2.85] NWC 1300 300 [-2.25, -1.13] [-3.39, -2.72] ICV 500 — [-2.39, -2.03] [-3.34, -2.65] FTA2 500 150 [-2.59, -2.04] [-3.44, -2.82] DHO38 750 200 [-2.78, -2.04] [-3.74, -2.71] GQD 550 150 [-2.54, -1.97] [-3.64, -2.75] NAA 800 300 [-2.45, -1.75] [-3.69, -2.93] NLK 400 150 [-2.87, -1.96] [-4.02, -3.45] NML 400 150 [-3.27, -2.35] [-4.00, -3.25]
下载: 导出CSV
-
Abel B, Thorne R M. 1998a. Electron scattering loss in Earth's inner magnetosphere: 1. Dominant physical processes. Journal of Geophysical Research: Space Physics, 103(A2): 2385-2396.
Abel B, Thorne R M. 1998b. Electron scattering loss in Earth's inner magnetosphere: 2. Sensitivity to model parameters. Journal of Geophysical Research: Space Physics, 103(A2): 2397-2407. doi: 10.1029/97JA02920
Agapitov O V, Artemyev A V, Mourenas D, et al. 2014. Inner belt and slot region electron lifetimes and energization rates based on AKEBONO statistics of whistler waves. Journal of Geophysical Research: Space Physics, 119(4): 2876-2893. doi: 10.1002/2014JA019886
Andrews M K. 1978. Non-ducted whistler-mode signals at low latitudes. Journal of Atmospheric and Terrestrial Physics, 40(4): 429-436, doi: 10.1016/0021-9169(78)90174-5.
Bortnik J, Inan U S, Bell T F. 2006a. Temporal signatures of radiation belt electron precipitation induced by lightning-generated MR whistler waves: 1. Methodology. Journal of Geophysical Research: Space Physics, 111(A2): A02204, doi: 10.1029/2005JA011182.
Bortnik J, Inan U S, Bell T F. 2006b. Temporal signatures of radiation belt electron precipitation induced by lightning-generated MR whistler waves: 2. Global signatures. Journal of Geophysical Research: Space Physics, 111(A2): A02205, doi: 10.1029/2005JA011398.
Claudepierre S G, Ma Q, Bortnik J, et al. 2020. Empirically estimated electron lifetimes in the Earth's radiation belts: Comparison with theory. Geophysical Research Letters, 47(3): e2019GL086056, doi: 10.1029/2019GL086056.
Clilverd M A, Horne R B. 1996. Ground-based evidence of latitude-dependent cyclotron absorption of whistler mode signals originating from VLF transmitters. Journal of Geophysical Research: Space Physics, 101(A2): 2355-2367, doi: 10.1029/95JA03153.
Clilverd M A, Jenkins B, Thomson N R. 2000. Plasmaspheric storm time erosion. Journal of Geophysical Research: Space Physics, 105(A6): 12997-13008, doi: 10.1029/1999JA900497.
Clilverd M A, Rodger C J, Gamble R, et al. 2008. Ground-based transmitter signals observed from space: Ducted or nonducted?. Journal of Geophysical Research: Space Physics, 113(A4): A04211, doi: 10.1029/2007JA012602.
Clilverd M A, Smith A J, Thomson N R. 1992a. The effects of ionospheric horizontal electron density gradients on whistler mode signals. Journal of Atmospheric and Terrestrial Physics, 54(7-8): 1061-1074, doi: 10.1016/0021-9169(92)90072-S.
Clilverd M A, Thomson N R, Smith A J. 1992b. Observation of two preferred propagation paths for whistler mode VLF signals received at a non-conjugate location. Journal of Atmospheric and Terrestrial Physics, 54(7-8): 1075-1079, doi: 10.1016/0021-9169(92)90073-T.
Cohen M B, Inan U S. 2012. Terrestrial VLF transmitter injection into the magnetosphere. Journal of Geophysical Research: Space Physics, 117(A8): A08310, doi: 10.1029/2012JA017992.
Gamble R J, Rodger C J, Clilverd M A, et al. 2008. Radiation belt electron precipitation by man-made VLF transmissions. Journal of Geophysical Research: Space Physics, 113(A10): A10211, doi: 10.1029/2008JA013369.
Graf K L, Inan U S, Piddyachiy D, et al. 2009. DEMETER observations of transmitter-induced precipitation of inner radiation belt electrons. Journal of Geophysical Research: Space Physics, 114(A7): A07205, doi: 10.1029/2008JA013949.
Gu W Y, Chen L J, Xia Z Y, et al. 2021. Direct evidence reveals transmitter signal propagation in the magnetosphere. Geophysical Research Letters, 48(15): e2021GL093987, doi: 10.1029/2021GL093987.
Gu X D, Wang Q S, Ni B B, et al. 2022. First results of the wave measurements by the WHU VLF wave detection system at the Chinese Great Wall station in Antarctica. Journal of Geophysical Research: Space Physics, 127(9): e2022JA030784, doi: 10.1029/2022JA030784.
Gu X D, Yi J, Wang S W, et al. 2023. Comparison of VLF signal responses to solar flares along daytime and nighttime propagation paths. Remote Sensing, 15(4): 1018, doi: 10.3390/rs15041018.
Han Y, Yuan J, Feng J L, et al. 2021. Automatic detection of "horizontal" electromagnetic wave disturbance in the data of EFD on ZH-1. Progress in Geophysics (in Chinese), 36(6): 2303-2311, doi: 10.6038/pg2021FF0157.
Han Y, Yuan J, Feng J L, et al. 2022. Automatic detection of 'horizontal' electromagnetic wave disturbance in the data of EFD on ZH-1. Progress in Geophysics (in Chinese), 37(1): 11-18, doi: 10.6038/pg2022FF0253.
Helliwell R A. 1965. Whistlers and Related Ionospheric Phenomena. Stanford, California: Stanford University Press.
Hua M, Li W, Ni B B, et al. 2020. Very-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space. Nature Communications, 11: 4847, doi: 10.1038/s41467-020-18545-y.
Hua M, Ni B B, Li W, et al. 2021. Statistical distribution of bifurcation of Earth's inner energetic electron belt at tens of keV. Geophysical Research Letters, 48(3): e2020GL091242, doi: 10.1029/2020GL091242.
Huang J P, Lei J G, Li S X, et al. 2018. The Electric Field Detector (EFD) onboard the ZH-1 satellite and first observational results. Earth and Planetary Physics, 2(6): 469-478. doi: 10.26464/epp2018045
Inan U S, Chang H C, Helliwell R A. 1984. Electron precipitation zones around major ground-based VLF signal sources. Journal of Geophysical Research: Space Physics, 89(A5): 2891-2906. doi: 10.1029/JA089iA05p02891
Kulkarni P, Inan U S, Bell T F, et al. 2008. Precipitation signatures of ground-based VLF transmitters. Journal of Geophysical Research: Space Physics, 113(A7): A07214, doi: 10.1029/2007JA012569.
Liu Y X Z, Xiang Z, Guo J G, et al. 2021. Scattering effect of very low frequency transmitter signals on energetic electrons in Earth's inner belt and slot region. Acta Physica Sinica (in Chinese), 70(14): 149401, doi: 10.7498/aps.70.20202029.
Liu Y X Z, Xiang Z, Ni B B, et al. 2022. Quasi-trapped electron fluxes induced by NWC transmitter and CRAND: Observations and simulations. Geophysical Research Letters, 49(5): e2021GL097443, doi: 10.1029/2021GL097443.
Ma Q L, Mourenas D, Li W, et al. 2017. VLF waves from ground-based transmitters observed by the Van Allen Probes: Statistical model and effects on plasmaspheric electrons. Geophysical Research Letters, 44(13): 6483-6491. doi: 10.1002/2017GL073885
Meredith N P, Horne R B, Clilverd M A, et al. 2019. An investigation of VLF transmitter wave power in the inner radiation belt and slot region. Journal of Geophysical Research: Space Physics, 124(7): 5246-5259, doi: 10.1029/2019JA026715.
Němec F, Santolík O, Hospodarsky G B, et al. 2022. Alpha transmitter signals observed by the Van Allen Probes: Ducted versus nonducted propagation. Geophysical Research Letters, 49(12): e2022GL098328, doi: 10.1029/2022GL098328.
Ni B B, Hua M, Gu X D, et al. 2022. Artificial modification of Earth's radiation belts by ground-based very-low-frequency (VLF) transmitters. Science China Earth Sciences, 65(3): 391-413. doi: 10.1007/s11430-021-9850-7
Parrot M, Inan U S, Lehtinen N G, et al. 2009. Penetration of lightning MF signals to the upper ionosphere over VLF ground-based transmitters. Journal of Geophysical Research: Space Physics, 114(A12): A12318, doi: 10.1029/2009JA014598.
Sauvaud J A, Maggiolo R, Jacquey C, et al. 2008. Radiation belt electron precipitation due to VLF transmitters: Satellite observations. Geophysical Research Letters, 35(5): L09101, doi: 10.1029/2008GL033194.
Sauvaud J A, Moreau T, Maggiolo R, et al. 2006. High-energy electron detection onboard DEMETER: The IDP spectrometer, description and first results on the inner belt. Planetary and Space Science, 54(5): 502-511. doi: 10.1016/j.pss.2005.10.019
Saxton J M, Smith A J. 1989. Quiet timeplasmaspheric electric fields and plasmasphere-ionosphere coupling fluxes at L=2.5. Planetary and Space Science, 37(3): 283-293, doi: 10.1016/0032-0633(89)90025-1.
Selesnick R S, Albert J M, Starks M J. 2013. Influence of a ground-based VLF radio transmitter on the inner electron radiation belt. Journal of Geophysical Research: Space Physics, 118(2): 628-635. doi: 10.1002/jgra.50095
Shen X H, Zhang X M, Yuan S G, et al. 2018. The state-of-the-art of the China Seismo-Electromagnetic Satellite mission. Science China Technological Sciences, 61(5): 634-642. doi: 10.1007/s11431-018-9242-0
Smith R L. 1961. Propagation characteristics of whistlers trapped in field-aligned columns of enhanced ionization. Journal of Geophysical Research, 66(11): 3699-3707. doi: 10.1029/JZ066i011p03699
Smith R L, Helliwell R A, Yabroff I W. 1960. A theory of trapping of whistlers in field-aligned columns of enhanced ionization. Journal of Geophysical Research, 65(3): 815-823. doi: 10.1029/JZ065i003p00815
Starks M J, Quinn R A, Ginet G P, et al. 2008. Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation. Journal of Geophysical Research: Space Physics, 113(A9): A09320, doi: 10.1029/2008JA013112.
Storey L R O. 1953. An investigation of whistling atmospherics. Philosophical Transactions of the Royal Society of London Series A, Mathematical and Physical Sciences, 246(908): 113-141. doi: 10.1098/rsta.1953.0011
Strangeways H J. 1981. Trapping of whistler-mode waves in ducts with tapered ends. Journal of Atmospheric and Terrestrial Physics, 43(10): 1071-1079. doi: 10.1016/0021-9169(81)90022-2
Tao X, Bortnik J, Friedrich M. 2010. Variance of transionospheric VLF wave power absorption. Journal of Geophysical Research: Space Physics, 115(A7): A07303, doi: 10.1029/2009JA015115.
Thorne R M, Horne R B. 1996. Whistler absorption and electron heating near theplasmapause. Journal of Geophysical Research: Space Physics, 101(A3): 4917-4928, doi: 10.1029/95JA03671.
Thomson N R. 1987. Experimental observations of very low latitude man-made whistler-mode signals. Journal of Atmospheric and Terrestrial Physics, 49(4): 309-319, doi: 10.1016/0021-9169(87)90027-4.
Xiang Z, Lin X H, Chen W, et al. 2021. Global morphology of NWC and NAA very-low-frequency transmitter signals in the inner magnetosphere: A survey using Van Allen Probes EMFISIS measurements. Chinese Journal of Geophysics (in Chinese), 64(11): 3860-3869, doi: 10.6038/cjg2021P0131.
Zhang Z X, Chen L J, Li X Q, et al. 2018. Observed propagation route of VLF transmitter signals in the magnetosphere. Journal of Geophysical Research: Space Physics, 123(7): 5528-5537, doi: 10.1029/2018JA025637.
Zhima Z, Zhou B, Zhao S F, et al. 2022. Cross-calibration on the electromagnetic field detection payloads of the China Seismo-Electromagnetic Satellite. Science China Technological Sciences, 65(6): 1415-1426, doi: 10.1007/s11431-021-1965-2.
韩莹, 袁静, 丰继林等. 2021. "张衡一号"电场探测仪数据水平状电磁波扰动自动检测. 地球物理学进展, 36(6): 2303-2311, doi: 10.6038/pg2021FF0157.
韩莹, 袁静, 丰继林等. 2022. 基于水平卷积核的"张衡一号"EFD数据水平状电磁波扰动自动检测. 地球物理学进展, 37(1): 11-18, doi: 10.6038/pg2022FF0253.
刘阳希子, 项正, 郭建广等. 2021. 甚低频台站信号对地球内辐射带和槽区能量电子的散射效应分析. 物理学报, 70(14): 149401, doi: 10.7498/aps.70.20202029.
项正, 林显浩, 陈薇等. 2021. 基于范阿伦双星EMFISIS观测数据的NWC和NAA人工甚低频台站信号的内磁层全球统计分布. 地球物理学报, 64(11): 3860-3869, doi: 10.6038/cjg2021P0131.
-
图(5)
表(2)
计量
- 文章访问数:
- PDF下载数:
- 施引文献: 0