学术论文

      近地微电离大气中阿尔芬波的截止

      Cut-off of Alfvén Waves in Weakly Ionized Near-Earth Atmosphere

      摘要:
      利用全电流双流体模型分析了地面磁扰动信号在近地层大气中的传播.结果表明磁扰动信号的传播模式受中性粒子离子碰撞频率、磁扰动频率、磁粘滞系数以及大气离化系数等参数的影响.中性粒子碰撞效应导致近地层大气中不存在阿尔芬波传播通道.当磁扰动频率远小于0.001 Hz时,磁扰动传播存在趋肤效应,且在近地大气中从高往下逐渐增强;当磁扰动频率远大于0.001 Hz时,磁扰动以类似于真空电磁波的模式在近地大气中传播.
      Abstract:
      Propagation of magnetic perturbation in the near-Earth atmosphere is associated with many applications,such as analysis of earthquake signals received by satellites and magnetic anomaly detection.These propagation properties are thought to be similar with those of electromagnetic waves in free space.However,some literatures show that magnetic perturbation signals also can penetrate into near-earth atmosphere by means of Alfvén waves,considering the effect of geomagnetic field.In this paper,the propagation properties of magnetic perturbation signal in the near-earth atmosphere,by using a total-current and two-fluid model,are studied.The results show that the propagation models of magnetic perturbation signal depend on the neutraral-ion collision frequency,the perturbation frequency,the coefficient of magnetic diffusion and the ionization fraction.Alfvén Waves cannot exist in the near-earth atmosphere because of neutral-ion collisions.When the frequency of magnetic perturbation is smaller than 0.001 Hz,the magnetic perturbation signals decay according to the skin effect,which increases as the height to the ground decreases.When the frequency of magnetic perturbation is larger than 0.001 Hz,the propagation of magnetic perturbation signal in the near-earth atmosphere is similar to that of electromagnetic wave in vacuum.
      Author: LIU Mingwei ZHANG Yutao LI Yanhua
      作者单位: 湖南科技大学物理与电子科学学院 湘潭411201
      刊 名: 空间科学学报 ISTICPKU
      年,卷(期): 2017, 37(4)
      分类号: P352
      在线出版日期: 2017年8月30日
      基金项目: 国家自然科学基金项目资助