The Effect of Solar Wind Variations on the Escape of Oxygen Ions From Mars Through Different Channels: MAVEN Observations
The Effect of Solar Wind Variations on the Escape of Oxygen Ions From Mars Through Different Channels: MAVEN Observations
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DOI：
10.1002/2017ja024741
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发表时间：
2017-11
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通讯作者：
E. Dubinin;M. Fraenz;M. Pätzold;J. Mcfadden;J. Halekas;G. DiBraccio;J. Connerney;F. Eparvier;David A. Brain;B. Jakosky;Oleg L Vaisberg;Lev Zelenyi
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作者：
E. Dubinin;M. Fraenz;M. Pätzold;J. Mcfadden;J. Halekas;G. DiBraccio;J. Connerney;F. Eparvier;David A. Brain;B. Jakosky;Oleg L Vaisberg;Lev Zelenyi
我们基于2014年11月1日至2016年5月15日的火星大气与挥发物演化（MAVEN）数据，展示了太阳风对火星离子逃逸通量影响的多仪器观测结果。研究了不同通道（等离子体片、磁瓣、边界层和离子羽流）中氧离子的损失随太阳风和行星际磁场变化的情况。我们利用修正的火星太阳电（MSE）坐标系来区分不同的逃逸路径。低能（≤30电子伏特）和高能（≥30电子伏特）离子的通量随太阳风动压、太阳风通量和运动电场的变化呈现出不同的趋势。主要的氧通量发生在感应磁层的尾部。太阳风运动电场导致离子通量不对称，并使来自不同半球供应尾部的离子通量与太阳风动压（或通量）以及运动电场之间产生不同的关系。高能氧离子逃逸的主要驱动因素是太阳风通量（或动压）。另一方面，低能离子成分呈现相反的趋势：离子通量随太阳风通量的增加而减少。结果，平均总氧离子通量随太阳风强度的变化较小。逃逸通量平均值的较大标准偏差表明存在能够增强或抑制离子逃逸效率的机制。研究表明，火星磁层具有复合磁层的特性，包含不同类别的磁力线。火星附近尾部闭合磁力线的存在可能是抑制离子逃逸通量的原因。
We present multi‐instrument observations of the effects of solar wind on ion escape fluxes on Mars based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) data from 1 November 2014 to 15 May 2016. Losses of oxygen ions through different channels (plasma sheet, magnetic lobes, boundary layer, and ion plume) as a function of the solar wind and the interplanetary magnetic field variations were studied. We have utilized the modified Mars Solar Electric (MSE) coordinate system for separation of the different escape routes. Fluxes of the low‐energy (≤30 eV) and high‐energy (≥30 eV) ions reveal different trends with changes in the solar wind dynamic pressure, the solar wind flux, and the motional electric field. Major oxygen fluxes occur through the tail of the induced magnetosphere. The solar wind motional electric field produces an asymmetry in the ion fluxes and leads to different relations between ion fluxes supplying the tail from the different hemispheres and the solar wind dynamic pressure (or flux) and the motional electric field. The main driver for escape of the high‐energy oxygen ions is the solar wind flux (or dynamic pressure). On the other hand, the low‐energy ion component shows the opposite trend: ion flux decreases with increasing solar wind flux. As a result, the averaged total oxygen ion fluxes reveal a low variability with the solar wind strength. The large standard deviations from the averages values of the escape fluxes indicate the existence of mechanisms which can enhance or suppress the efficiency of the ion escape. It is shown that the Martian magnetosphere possesses the properties of a combined magnetosphere which contains different classes of field lines. The existence of the closed magnetic field lines in the near‐Mars tail might be responsible for suppression of the ion escape fluxes.