當行星的磁層受到太陽風的壓縮時，會令磁層的強度增加，我們可以使用受到壓縮的磁層磁場與行星純磁偶極場之間的比值來衡量磁層受壓縮的程度。對地球來說，此比值與日下點距離的增加成正比。但我們使用MESSENGER衛星的資料對水星磁層進行分析後發現，水星的趨勢與地球相反，在磁層頂靠近水星時反而有著更高的壓縮率，這是由於水星核心表面的感應磁場增加了日側磁場的強度。除此之外我們還分析了在南向與北向行星際磁場之間，水星磁層頂日下點距離是否有所差異。過去的研究沒有觀察到顯著的差異存在，然而我們的研究顯示在較高的行星際磁場Z分量下，水星日下點距離存在著具有統計顯著性的差異。在北向行星際磁場的條件下，極尖區後方的磁重聯將磁通量由磁尾傳輸到日側磁層，進而增加了磁層頂日下點距離。而南向行星際磁場造成的磁場侵蝕能夠被核心的感應磁場所補償。;When a planet’s magnetosphere is compressed by the solar wind, the magnetic field intensity of its magnetosphere increases. This compression can be measured by the ratio of the compressed magnetic field to the planet′s dipole field. The ratio is directly proportional to the subsolar standoff distance of the magnetopause for Earth. However, our analysis using magnetopause crossing data from the MESSENGER satellite reveals a contrary trend. The compression rate is higher when Mercury’s magnetopause is closer to its center, indicating that the induced magnetic field on the surface of Mercury′s core enhances the intensity of the dayside magnetic field. In addition, previous studies suggested that there are no differences on Mercury’s subsolar standoff distance between the north–south polarities of the interplanetary magnetic field (IMF). However, our research shows statistically significant differences under higher IMF BZ component (15–20 nT). Magnetic reconnection behind the cusp transports magnetic flux from the magnetotail to the dayside magnetosphere under northward IMF condition, resulting in an increased distance of the subsolar standoff distance. The induced magnetic fields compensate the eroded magnetic flux for a large southward IMF.
