Detection of ultralow‐frequency cavity modes using spacecraft data
Detection of ultralow‐frequency cavity modes using spacecraft data
复制标题
DOI：
10.1029/2001ja000224
复制
发表时间：
2002-10
影响因子：
--
通讯作者：
C. Waters;Kazue Takahashi;Dong‐Hun Lee;B. Anderson
中科院分区：
文献类型：
--
作者：
C. Waters;Kazue Takahashi;Dong‐Hun Lee;B. Anderson
[1]地球磁层中的冷磁化等离子体支持两种超低频等离子体波模式。这两种模式都可能在磁层空穴中表现出共振振荡。理论和数值研究都预测了腔/波导谐振模的存在，但实验证据很少。在本文中，我们使用一维(1-D)和三维(3-D)磁流体(MHD)数值模型详细描述了这些模式的预期结构。为了开发适用于航天器电场和磁场扰动数据的实验检测方法，对腔/波导模结构进行了研究。一维模型中的腔模共振提出了一种基于波极化的检测方法，该方法利用径向(BX)和场向(BZ)的磁扰动。然而，当实施时，这种方法不能识别由主动磁层粒子示踪器探测器/CCE记录的磁场数据中的空腔/波导模式，对于在方位(BY)通道中显示显著场线共振的事件。对三维MHD数值模拟数据的检验表明，在BZ分量数据中，腔/波导谐振特征识别效果最好。在此基础上，讨论了一种利用空间上分离的两颗卫星的BZ数据进行波模检测的方法。ISEE-1和ISEE-2航天器的磁力仪数据实例表明，即使当BZ数据的相干长度小于0.4RE时，BY数据中也会出现场线共振。
[1] The cold, magnetized plasma in the Earth's magnetosphere supports two ultralow- frequency plasma wave modes. Both these modes may exhibit resonant oscillations in the magnetosphere cavity. Theoretical and numerical studies have predicted the existence of cavity/waveguide resonance modes, yet experimental evidence is sparse. In this paper we detail the expected structure of these modes using both one dimensional (1-D) and three-dimensional (3-D) magnetohydrodynamic (MHD) numerical models. The cavity/waveguide mode structures are examined in order to develop experimental detection methods suitable for spacecraft electric and magnetic field perturbation data. Cavity mode resonances in the 1-D model suggest a detection method based on wave polarization using the radial (bx) and field-aligned (bz) magnetic perturbations. However, when implemented, this method failed to identify cavity/waveguide modes in the magnetic field data recorded by Active Magnetospheric Particle Tracer Explorers/CCE for events that showed pronounced field line resonances in the azimuthal (by) channel. An examination of data from a 3-D MHD numerical simulation showed that the cavity/waveguide resonant signature was identified best in bz component data. Consequently, a wave mode detection method using the bz data from two spatially separated satellites is discussed. Magnetometer data examples from the ISEE 1 and 2 spacecraft show that field line resonances appear in the by data even when the coherence length of the bz data is less than 0.4 RE.