ULF Wave‐Associated Density Irregularities and Scintillation at the Equator
ULF Wave‐Associated Density Irregularities and Scintillation at the Equator
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赤道处 ULF 波相关的密度不规则性和闪烁
DOI：
10.1029/2018gl078163
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发表时间：
2018
影响因子：
5.2
通讯作者：
Z. Bamba
中科院分区：
文献类型：
--
作者：
E. Yizengaw;E. Zesta;M. Moldwin;M. Magoun;N. Tripathi;C. Surussavadee;Z. Bamba
本文介绍了独立的多仪器观测，这些观测解决了超低频（ULF）波相关电场如何引发赤道电离层密度波动和闪烁的物理机制。由于赤道的磁场完全嵌入在相对高碰撞和高导电性的介质中，因此由于极低频波的活动，地磁场可能不可能波动。这意味着赤道上的波动电场可能不是由于磁场波动而通过赤道发电机作用产生的。相反，电场从高纬度穿透，产生波动的磁场，并调制垂直漂移，从而导致赤道地区的密度波动。我们通过在低纬度地区应用适当的衰减因子来估计高纬度地区和赤道地区极低频波相关的波动电场来证明这一点。电场和密度波动的周期都在6 ~ 9 min之间，这是在Pc5范围内ULF波的典型周期。由于与其他极低频波频带相比，Pc5波相关电场的振幅大，周期长，甚至可以使用低灵敏度和低采样率（例如1分钟）的磁图来估计，它可以很容易地渗透到低纬度地区，并产生显著的电离层密度波动，这种波动足以在赤道地区产生闪烁。
This paper presents independent multi‐instrument observations that address the physical mechanisms of how ultralow‐frequency (ULF) wave‐associated electric fields initiate ionospheric density fluctuation and scintillation at the equator. Since the magnetic field at the equator is entirely embedded in a relatively high‐collision and high‐conductivity medium, the condition may not be possible for the geomagnetic field to fluctuate due to ULF wave activity. This implies that the fluctuating electric field at the equator may not be produced through equatorial dynamo action due to fluctuating magnetic fields. Instead, the electric field penetrates from high latitudes and produces fluctuating magnetic field as well as modulates the vertical drift and hence causes the density to fluctuate at the equatorial region. We demonstrate this by estimating the ULF associated fluctuating electric field at high latitudes and at the equatorial region by applying the appropriate attenuation factor as it penetrates to lower latitudes. The periodicity of both electric field and density fluctuations appears to be between 6 and 9 min, which is a typical period of ULF waves in the Pc5 range. Because of its large amplitude and long periods compared to other ULF wave frequency bands, the Pc5 wave‐associated electric field, which can even be estimated using magnetograms with low sensitivity and low sampling rate (e.g., 1 min), can easily penetrate to the lower latitude region and produce significant ionospheric density fluctuations that can be strong enough to create scintillation at the equatorial region.