We have used Mars Express (MEX) and Mars Global Surveyor (MGS) simultaneousand non-simultaneous measurements to study the Martian plasma environment. Inparticular, we have derived quantitative expressions for the altitude of theterminator bow shock (BS) and magnetic pileup boundary (MPB) as functions ofsolar wind dynamic pressure, crustal magnetic fields and solar EUV flux. Wehave also studied the influence of the interplanetary magnetic field (IMF)direction. Through simultaneous two-spacecraft case studies we have shownthat the dynamic pressure has a strong influence on the location and shape ofthese boundaries, which is also confirmed through a large statistical study.A higher dynamic pressure pushes the boundaries downward. The IMF directionhas a weaker but still significant influence on both boundaries and causesthem to move outward in the hemisphere of locally upward electric field.However, the MPB in the Southern Hemisphere is found to actually move inwardwhen the electric field is directed locally upward. The crustal magneticfields in the Southern Hemisphere have a strong influence on the MPB andcause it to move to higher altitudes over strong crustal magneticfields. The influence of the crustal magnetic fields on the BS is moreambiguous since there are few crossings over the strongest crustal fields,but there appears to be at least a small trend of a higher BS for strongercrustal fields. An increased solar EUV flux has been found to cause the BS tomove outward and the MPB to move inward.
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机译：我们已使用Mars Express（MEX）和Mars Global Surveyor（MGS）同时进行和非同时进行测量来研究火星等离子体环境。尤其是，我们推导了终结者弓形冲击（BS）和磁堆积边界（MPB）的高度随太阳风动压，地壳磁场和太阳EUV通量的函数的定量表达式。我们还研究了行星际磁场（IMF）方向的影响。通过同时进行的两个航天器的案例研究，我们发现动压对这些边界的位置和形状有很大的影响，这也被大量的统计研究证实了。更高的动压将边界向下推。 IMF方向对这两个边界都具有较弱但仍然很重要的影响，并导致它们在局部向上电场的半球中向外移动，但是，发现南半球的MPB实际上在电场向上定向时向内移动。南半球的地壳磁场对MPB有很强的影响，并使其在强地壳磁场上方移动到更高的高度。地壳磁场对BS的影响更加明确，因为在最强地壳上几乎没有交叉，但是对于强地壳场，似乎至少有一个小趋势，即更高的BS。已经发现增加的太阳EUV通量会导致BS向外移动，MPB向内移动。
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