Dependence of O+ escape rate from the Venusian upper atmosphere on IMF directions
Dependence of O+ escape rate from the Venusian upper atmosphere on IMF directions
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DOI：
10.1002/grl.50392
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发表时间：
2013-05
影响因子：
5.2
通讯作者：
K. Masunaga;Y. Futaana;G. Stenberg;S. Barabash;Tinglong Zhang;A. Fedorov;Shoichi Okano;Naoki Terada
中科院分区：
文献类型：
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作者：
K. Masunaga;Y. Futaana;G. Stenberg;S. Barabash;Tinglong Zhang;A. Fedorov;Shoichi Okano;Naoki Terada
我们使用空间等离子体和高能原子分析仪（ASPERA-4）和金星快车上的磁力计（MAG）的数据，研究了O+逃逸率对上游行星际磁场（IMF）方向的依赖性。我们考虑两种情况，即垂直IMF的情况（167起事件）和与之平行的国际货币基金组织案（82个事件），其中IMF几乎垂直于金星-太阳线，几乎平行于它。通过积分在夜面观察到的O+通量，结果表明，O+逃逸率分别为（5.8 ± 2.9）× 1024 s-1（垂直IMF情况）和（4.9 ± 2.2）× 1024 s-1（平行IMF情况）.由于这些值没有显着差异，上游IMF方向不影响O+从金星流出的总量。不同的加速机制必须相互平衡，以保持逃逸率相同。
We investigate the dependence of the O+ escape rate on the upstream interplanetary magnetic field (IMF) direction by using data from the Analyser of Space Plasma and Energetic Atoms (ASPERA‐4) instrument and the magnetometer (MAG) onboard Venus Express. We consider two cases, namely the perpendicular IMF case (167 events) and the parallel IMF case (82 events), where IMF is nearly perpendicular to the Venus‐Sun line and nearly parallel to it. By integrating O+ fluxes observed on the nightside, total O+ escape rates of (5.8 ± 2.9) × 1024 s−1 (perpendicular IMF case) and (4.9 ± 2.2) × 1024 s−1 (parallel IMF case) are obtained. As these values are not significantly different, the upstream IMF direction does not affect the total amount of O+ outflow from Venus. The different acceleration mechanisms must balance each other in order to keep the escape rate the same.