Mercury's sodium exosphere: Magnetospheric ion recycling
Mercury's sodium exosphere: Magnetospheric ion recycling
复制标题
水星的钠外逸层：磁层离子回收
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
Robert E. Johnson
中科院分区：
文献类型：
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作者：
F. Leblanc;D. Delcourt;Robert E. Johnson
[1]水星中性钠系外圈的三维蒙特卡罗模型被用来描述观测到的系外层密度变化与钠表面浓度沿水星绕太阳运动的变化之间的关系[勒布朗和约翰逊，2003]。考虑了四个抛射过程：热解吸和光子激发解吸、太阳风溅射和微流星体蒸发。这是一个由DelCourt等人开发的水星磁层离子循环模型。[2002,2003]被用来研究钠磁层离子再循环的贡献。该模型被耦合到外圈模型，以跟踪水星外圈中形成的新的电离钠。用Na+和Na+耦合模型研究了离子的再碰撞溅射和注入。由于磁层离子溅射的通量很小，所以磁层离子溅射对喷入水星外层的钠原子总量的贡献不大；然而，注入水星表面的磁层离子充分集中在狭窄的纬度带内，从而提高了局部钠的表面浓度。当注入的钠暴露在日侧终结点附近的太阳通量中时，这种增强被认为是在高纬度观察到的水星外层钠排放的峰值。
[1] A three-dimensional Monte Carlo model of Mercury's neutral sodium exosphere was used to describe correlation between the observed variations in the exospheric density and the variations in the surface concentration of sodium along Mercury's motion around the Sun [Leblanc and Johnson, 2003]. Four processes of ejection were taken into account: thermal and photon stimulated desorptions, solar wind sputtering, and micrometeoroid vaporization. Here a model of ion circulation in Mercury's magnetosphere developed by Delcourt et al. [2002, 2003] is used to examine the contribution from sodium magnetospheric ion recycling. The model is coupled to the exospheric model to track newly ionized sodium formed in Mercury's exosphere. The coupled Na and Na+ model is used to examine the sputtering by and implantation of the reimpacting ions. The magnetospheric ion sputtering does not contribute significantly to the total amount of Na atoms ejected into Mercury's exosphere because of its rather small flux; however, magnetospheric ion implantation in Mercury's surface is sufficiently concentrated inside narrow latitude bands to enhance the local surface concentration of sodium. This enhancement is seen to contribute to the peaks in Mercury's exospheric sodium emission observed at high latitudes when the implanted sodium is exposed to the solar flux near the dayside terminator.