Effect of the solar wind on the nature of arbitrary amplitude ion-acoustic solitary waves in Venus’ upper ionosphere
Effect of the solar wind on the nature of arbitrary amplitude ion-acoustic solitary waves in Venus’ upper ionosphere
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太阳风对金星上层电离层任意振幅离子声孤立波性质的影响
DOI：
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发表时间：
2022
影响因子：
4.8
通讯作者：
W. Moslem
中科院分区：
文献类型：
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作者：
S. Salem;A. Fayad;N. A. El;F. Sayed;M. Shihab;H. Fichtner;M. Lazar;W. Moslem
观测表明，在 1000 - 2000 公里的高度，太阳风与金星电离层等离子体之间的相互作用导致离子声波 (IAW) 的形成。为了研究这一假设，基于先锋金星轨道飞行器（PVO）和金星快车（VEX）的观测数据开发了一个合适的流体动力学模型。它由两种正离子、氢 (H+) 和氧 (O+) 电离层流体以及与流动的太阳风质子和等温太阳风电子相互作用的等温电离层电子组成。检查了全非线性 IAW 的有利条件和传播特性及其对太阳风参数的依赖性，并与可用的空间观测进行了比较。研究发现，通过增加太阳风质子或电子的温度，脉冲幅度会减小。相反，太阳风质子的相对密度或速度较高，会放大孤立结构的振幅。此外，只有在称为等离子体速度尺度的一定范围内的速度变化才能影响孤立脉冲的基本特征。超过这个尺度，孤立波就不再受到太阳风质子速度的影响。该理论模型预测最大电场为 7.5 mV/m、脉冲持续时间为 3 ms 的静电孤立波的传播。电场脉冲的快速傅立叶变换 (FFT) 功率谱的输出是频率范围为 ∼0.1 − 4 kHz 的宽带静电噪声。这些 FFT 计算与 PVO 的观察结果非常吻合。
Observations suggest that at altitudes of 1000 − 2000 km the interaction between the solar wind and Venus’ ionospheric plasma leads to ion-acoustic waves (IAWs) formation. For studying this hypothesis, a suitable hydrodynamic model relying on the observational data from Pioneer Venus Orbiter (PVO) and Venus Express (VEX) is developed. It consists of two ionospheric fluids of positive ions, hydrogen (H+) and oxygen (O+), and isothermal ionospheric electrons interacting with streaming solar wind protons and isothermal solar wind electrons. The favourable conditions and propagation characteristics of the fully nonlinear IAWs along with their dependence on solar wind parameters are examined and compared with the available space observations. It is found that the pulse amplitude is decreased by increasing the temperature of either the solar wind protons or electrons. In contrast, a higher relative density or velocity of the solar wind protons amplifies the amplitude of the solitary structures. Moreover, only velocity variations within a certain range called the plasma velocity scale can affect the basic features of the solitary pulses. Beyond this scale, solitary waves are not affected by the solar wind protons’ velocity anymore. This theoretical model predicts the propagation of electrostatic solitary waves with a maximum electric field of 7.5 mV/m and a pulse time duration of 3 ms. The output of the fast Fourier transformation (FFT) power spectra of the electric field pulse is a broadband electrostatic noise in a frequency range of ∼0.1 − 4 kHz. These FFT calculations are in good agreement with PVO’s observations.