Martian Bow Shock Oscillations: Simultaneous Observations from Tianwen-1 and MAVEN

Martian bow shock, the first barrier of defense against the solar wind, reflects the complex interplay between the solar wind and Martian upper atmosphere and crustal fields. Typically an orbiter crosses the bow shock once a time on every inbound or outbound orbit. It is also possible that an orbiter crosses the bow shock multiple times due to the quick oscillation of the bow shock. Here we present direct evidence of such a phenomenon through five events observed simultaneously by Tianwen-1 and MAVEN. During these events, Tianwen-1 observed minute-scale oscillations of the bow shock with spatial extents of hundreds of kilometers, while MAVEN monitored the upstream solar wind conditions. It is reasonably found that the solar wind dynamic pressure change or the IMF rotation led to the quick oscillations in three events. However, in other two events, we unexpectly found that the Martian bow shock oscillated under a quasi-steady solar wind condition. This study emphasizes the importance of joint observations by Tianwen-1 and MAVEN for understanding the interaction between the solar wind and Martian induced magnetosphere.