Magnetosheath electrostatic turbulence
Magnetosheath electrostatic turbulence
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磁鞘静电湍流
DOI：
10.1029/ja084ia03p00917
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发表时间：
1979
影响因子：
--
通讯作者：
P. Rodriguez
中科院分区：
文献类型：
--
作者：
P. Rodriguez
利用美国爱荷华大学Imp - 6卫星等离子体波实验的测量结果，对地球磁鞘中的静电等离子体波谱进行了研究。静电等离子体波湍流几乎连续存在于整个磁鞘中，具有宽带（20 Hz至70 kHz）场强度，一般为0.01-1.0 mV m - 1。在电子等离子体频率（30-60 kHz）附近，偶有检测到约1.0 mV m−1的峰值强度。在磁鞘静电湍流的频谱中，通常可以识别出两种或三种成分：高频（≥30 kHz）成分，其峰值位于电子等离子体频率fpe，低频成分，其宽强度最大值低于名义离子等离子体频率fpi (~ fpe/43)，以及在fpi <f < fpe范围内定义不太明确的中间成分。磁鞘静电湍流的强度分布清楚地表明，低频分量与弓形激波有关，表明在激波处开始的离子加热持续到下游的磁鞘。低于1khz的静电波沿磁场方向极化，结果与冲击时静电波的极化一致。高频和中频成分是磁鞘谱的特征，不是激波谱的特征，但经常在上游太阳风中检测到。磁鞘等离子体频率处的静电湍流强度分布与激波没有明显的相关性，表明电子等离子体振荡是磁鞘的普遍特征。等离子体波噪声显示出在黎明和黄昏区域减小的趋势，这与远离太阳下磁鞘的湍流的总体减小是一致的。偶尔会发生强烈的静电爆发，这与磁场梯度和波动有关，可能表明存在强电流系统，例如在磁层顶可能发生的强电流系统。
By using measurements with the University of Iowa plasma wave experiment on the Imp 6 satellite a study has been conducted of the spectrum of electrostatic plasma waves in the terrestrial magnetosheath. Electrostatic plasma wave turbulence is almost continuously present throughout the magnetosheath with broadband (20 Hz to 70 kHz) rms field intensities typically 0.01–1.0 mV m−1. Peak intensities of about 1.0 mV m−1 near the electron plasma frequency (30–60 kHz) have been detected occasionally. Two or three components can usually be identified in the spectrum of magnetosheath electrostatic turbulence: a high-frequency (≥30 kHz) component peaking at the electron plasma frequency fpe, a low-frequency component with a broad intensity maximum below the nominal ion plasma frequency fpi (∼fpe/43), and a less well defined intermediate component in the range fpi <f < fpe. The intensity distribution of magnetosheath electrostatic turbulence clearly shows that the low-frequency component is associated with the bow shock, suggesting that the ion heating begun at the shock continues into the downstream magnetosheath. Electrostatic waves below 1 kHz are polarized along the magnetic field direction, a result consistent with the polarization of electrostatic waves at the shock. The high- and intermediate-frequency components are features of the magnetosheath spectrum which are not characteristic of the shock spectrum but are often detected in the upstream solar wind. The intensity distribution of electrostatic turbulence at the magnetosheath plasma frequency has no apparent correlation with the shock, indicating that electron plasma oscillations are a general feature of the magnetosheath. The plasma wave noise shows a tendency to decrease toward the dawn and dusk regions, consistent with a general decrease in turbulence away from the subsolar magnetosheath. Occasionally, intense electrostatic bursts occur which are correlated with magnetic field gradients and fluctuations, possibly indicating the presence of strong current systems such as can occur at the magnetopause.