Effects of the 2007 Martian Global Dust Storm on Boundary Positions in the Induced Magnetosphere

Mars's magnetosphere is a sensitive system, varying due to external and internal factors, such as solar wind conditions and crustal magnetic fields. A signature of this influence can be seen in the position of two boundaries; the bow shock and the induced magnetospheric boundary (IMB). The bow shock moves closer to Mars during times of high solar activity, and both the bow shock and IMB bulge away from Mars over crustal magnetic fields in the southern hemisphere. This study investigates whether large-scale atmospheric events at Mars have any signature in these two magnetic boundaries, by investigating the 2007 storm. The 2007 global storm lasted for several months and increased atmospheric temperatures and densities of both water vapor and carbon dioxide in the atmosphere, leading to an increase in atmospheric escape. Using Mars Express, we identified boundary locations before, during, and after the event, and compared these to modeled boundary locations and areographical locations on Mars. We find that, while it is unclear whether the bow shock position is impacted by the storm, the IMB location does change significantly, despite the orbital bias introduced by Mars Express. The terminator distance for the IMB peaks at longitudes 0°–40° and 310°–360°, leaving a depression around 180° longitude, where the boundary usually extends to higher altitudes due to the crustal magnetic fields. We suggest this may be due to the confinement of ionospheric plasma over crustal fields preventing mixing with the dust, creating a dip in ionospheric pressure here.

火星的磁层是一个敏感的系统，由于外部和内部因素（如太阳风状况和地壳磁场）而发生变化。这种影响的一个特征可以在两个边界的位置上看到：弓形激波和感应磁层边界（IMB）。在太阳活动剧烈时，弓形激波会更靠近火星，并且弓形激波和IMB在南半球的地壳磁场上方都会远离火星凸起。这项研究通过对2007年的风暴进行研究，来调查火星上的大规模大气事件在这两个磁边界中是否有任何特征。2007年的全球性风暴持续了数月，使大气温度以及大气中水蒸气和二氧化碳的密度增加，导致大气逃逸加剧。利用“火星快车”号，我们确定了事件发生前、发生期间和发生后的边界位置，并将这些位置与模拟的边界位置以及火星上的地理位置进行了比较。我们发现，虽然弓形激波的位置是否受到风暴影响尚不清楚，但IMB的位置确实发生了显著变化，尽管“火星快车”号存在轨道偏差。IMB的晨昏线距离在经度0° - 40°和310° - 360°处达到峰值，在经度180°左右出现凹陷，由于地壳磁场的作用，该边界通常会延伸到更高的高度。我们认为这可能是由于电离层等离子体在地壳磁场上方受到限制，无法与尘埃混合，从而导致此处电离层压力下降。