Characteristic analysis and full wave simulation of electrical field for China seismo-electromagnetic satellite observations radiated from VLF transmitter
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摘要:
中国地震电磁监测试验卫星张衡一号（ZH-1）已于2018年2月2日成功发射，正在开展卫星数据在轨测试，并对卫星数据质量进行判定.本文对ZH-1卫星2018年5月至6月夜侧的VLF频段电场功率谱数据进行了分析.通过分析位于不同L值、具有不同发射频率的多个VLF人工源上空的卫星重访轨道观测数据，发现ZH-1卫星记录的人工源信号电场变化标准差与DEMETER卫星记录电场变化标准差几乎一致，说明ZH-1卫星观测数据具有较好的稳定性.通过重访轨道均值与全波模型计算结果对比，发现两者在数值上较为接近，在形态上较为一致，说明ZH-1卫星VLF频段电场功率谱数据具有一定的可靠性.此外，研究了VLF人工源上空及共轭区的电场分布特征和电波传播规律，并与DEMETER卫星的结果进行了对比，结果表明VLF人工源产生的电磁辐射穿透电离层后以导管或者非导管的哨声波模向共轭区传播，因为传播过程中的朗道阻尼，共轭区的电场能量比辐射源顶空更小.VLF人工源位于L < 1.5时，电磁波传播更容易发生非导管传播，VLF人工源信号导管传播模式在共轭区的电场响应相对于共轭点会发生一定程度北向偏移.
Abstract:The China seismo-electromagnetic satellite (ZH-1) has been successfully launched on February 2nd, 2018. In-orbit test on the satellite data is undergoing, and meanwhile, the quality of the scientific data needs to be verified. The VLF electric field power spectrum data at night-side of ZH-1 from May to June 2018 has been analyzed. The re-orbit data above the VLF transmitters at different L shell with different radiation frequencies have been analyzed. It can be found that the standard deviation of the electric field excited by the VLF transmitters observed by the ZH-1 satellite is similar with DEMETER satellite. The observed electric fields are generally consistent with the full-wave simulation results, which mean that ZH-1 satellite's electric field PSD data at VLF band is stable and reliable. In addition, the electric field distribution and the propagation mode of the signal from the VLF transmitters have also been studied above the transmitters and their conjugate regions. The results show that the electromagnetic waves penetrating the lower ionosphere propagate in the way of the 'duct' or the 'non-duct' whistler mode to the topside of VLF transmitter and its conjugate region. Because of the Landau damping, the electromagnetic energy reaching the conjugate region is usually smaller than it just above the transmitter. It is easier for the VLF transmitters located at L < 1.5 to propagate as the 'non-duct' whistler mode. The electric field distribution has northward displacement at the conjugate region for the 'duct' mode.
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Key words:
- Terrestrial VLF transmitter /
- ZH-1 Satellite /
- Full-wave model
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图 3
ZH-1(第一行)与DEMETER(第二行)卫星记录的VLF人工源(NWC, GBZ, NAA, NPM)激发的电场
Figure 3.
The electric field excited by VLF transmitters (NWC, GBZ, NAA, NPM) record by ZH-1 (first panel) and DEMETER (second panel)
图 5
ZH-1卫星(第一行)和DEMETER卫星(第二行)记录的VLF人工源(NWC, NAA, NPM)激发的电场对比
Figure 5.
The electric field excited by VLF transmitters (NWC, NAA, NPM) record by ZH-1(first panel) and DEMETER (second panel) satellite
图 6
ZH-1卫星记录的VLF人工源(NWC, NAA, NPM)激发的电场与模拟结果对比
Figure 6.
Comparison of electric field excited by VLF transmitter (NWC, NAA, NPM) between ZH-1 satellite observation and simulation results
表 1
VLF人工源分布及参数
Table 1.
The parameters of VLF transmitters
名称 纬度(°N) 经度(°E) L值 地磁倾角(°) 地磁偏角(°) 频率(kHz) 工作模式 NWC -21.82 114.17 1.32 -55.3 0.5 19.80 MSK GBZ 54.91 -3.28 2.48 67.4 -3.8 19.80 MSK NAA 44.65 -67.28 2.46 71 -12.2 24.00 MSK NPM 21.42 -158.15 1.14 38.0 9.9 21.40 MSK 
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