A technique to investigate plasma mass density in the topside ionosphere using ULF waves
A technique to investigate plasma mass density in the topside ionosphere using ULF waves
复制标题
使用 ULF 波研究顶部电离层等离子体质量密度的技术
DOI：
10.1029/1999ja900042
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发表时间：
1999
影响因子：
--
通讯作者：
B. J. Fraser
中科院分区：
文献类型：
--
作者：
I. A. Price;C. Waters;F. Menk;G. J. Bailey;B. J. Fraser
电离层与等离子体层混合的区域中相对较冷的核心等离子体密度很难通过实验探测。结果表明，超低频磁流体动力波的共振可以提供有关电离层和等离子体层合并区域的等离子体质量密度的独特信息。该技术依赖于 ULF 场线谐振谐波的检测，并允许确定沿磁场线离散位置处的等离子体质量密度，而无需假设沿场的等离子体分布的任何函数。从 L=1.8 处的 ULF 谐波获得的等离子体质量密度与该区域的几个等离子体质量密度模型进行了比较。除了描述和说明该技术之外，还对该方法的局限性进行了严格的检查。其中包括可检测到的 ULF 谐波的有限数量、非线性求解方案的复杂性、在较大 L 值下使用该方法的后果，以及使用有限差分方案逼近方程组。结果表明，该技术可以在离散的磁场对齐高度上提供等离子体质量密度的独立估计，这为预测从顶部电离层到内部等离子体层的等离子体动力学的理论模型提供了额外的实验检查。
The relatively cold core plasma density in the region where the ionosphere mixes with the plasmasphere is difficult to probe experimentally. It is shown that resonances of ULF magnetohydrodynamic waves can provide unique information on plasma mass density in the region where the ionosphere and plasmasphere merge. The technique depends on the detection of harmonics of ULF field line resonances and allows the determination of plasma mass densities at discrete locations along a magnetic field line without assuming any function for plasma distribution along the field. The plasma mass densities obtained from ULF harmonics at L=1.8 are compared with several plasma mass density models of this region. In addition to describing and illustrating the technique, the method is critically examined for its limitations. These include the finite number of ULF harmonics that can be detected, the complexity of the nonlinear solving scheme, the consequences of using the method at larger L values, and approximating the system of equations with a finite difference scheme. It is shown that the technique can provide independent estimates of plasma mass densities at discrete, magnetic field-aligned altitudes, which gives an additional experimental check on theoretical models that predict the dynamics of plasma from the topside ionosphere to the inner plasmasphere.