The spectral scalings of magnetic fluctuations upstream and downstream of the Venusian bow shock
The spectral scalings of magnetic fluctuations upstream and downstream of the Venusian bow shock
复制标题
金星弓形激波上游和下游磁波动的光谱尺度
DOI：
10.1186/s40623-020-01343-7
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发表时间：
2021
影响因子：
3
通讯作者：
Zhang T. L.
中科院分区：
文献类型：
--
作者：
Xiao S. D.;Wu M. Y.;Wang G. Q.;Chen Y. Q.;Zhang T. L.
我们统计研究了金星弓形激波附近上游和下游区域磁涨落的光谱尺度，并通过激波几何形状进行微分。根据金星快车数据，选择了115个准平行（）弓形激波道口和303个准垂直（）弓形激波道口。统计结果表明，在磁波动穿过弓激波后，弓激波倾向于将磁流体动力学（MHD）区域中的上游光谱修正为更平坦的1/f噪声，而将动力学区域中的上游光谱修正为更陡峭的湍流，并且这种修正对于弓激波来说是基本一致的。然而，上游谱尺度与激波几何形状相关。弓激波附近磁涨落谱尺度的变化不如弓激波交叉点附近那么显着。这可能是由回流离子产生的波动引起的，这些离子可以穿过弓激波逃逸到前震中。我们的研究结果表明，金星附近的能量级联和耗散可以通过金星弓形激波来改变，并且弓形激波在太阳风与金星相互作用中的能量注入和耗散中起着重要作用。谱标度的大分散性表明这种波动环境是复杂的，激波几何结构并不是金星弓形激波波动的唯一关键因素。未来将探讨对上游波动进行冲击修正的其他可能因素。
We statistically investigate the spectral scalings of magnetic fluctuations at the upstream and downstream regions near the Venusian bow shock and perform a differentiation by shock geometry. Based on the Venus Express data, 115 quasi-parallel () bow shock crossings and 303 quasi-perpendicular () bow shock crossings are selected. The statistical results suggest that the bow shock tends to modify the upstream spectra flatter to 1/fnoise in the magnetohydrodynamics (MHD) regime and steeper to turbulence in the kinetic regime after the magnetic fluctuations crossing the bow shock, and this modification for theandbow shocks is basically consistent. However, the upstream spectral scalings are associated with the shock geometry. The changes of the spectral scalings of magnetic fluctuations near thebow shocks are not as significant as near thebow shock crossings. That might result from the fluctuations generated by the backstreaming ions which can escape across thebow shock into the foreshock. Our results suggest that the energy cascade and dissipation near Venus can be modified by the Venusian bow shock, and thebow shock plays an important role on the energy injection and dissipation in the solar wind interaction with Venus. The large dispersion of spectral scalings indicates that this fluctuation environment is complicated, and the shock geometry is not the only key factor in the fluctuations across the Venusian bow shock. Other possible factors in the shock modification to the upstream fluctuations will be explored in future.