Title: Magnetic flux ropes within reconnection exhausts close to the centers of heliospheric current sheets near the Sun Show Chinese title

Title: 重联排气中靠近太阳附近日球电流片中心的磁通量绳

Abstract: Understanding the relationship between magnetic flux ropes and magnetic reconnection is fundamental to both space and astrophysical plasma studies. In this study, we report on two consecutive heliospheric current sheet (HCS) crossings by Parker Solar Probe (PSP), separated by ~10.5 hours, at a heliocentric distance of ~12 solar radii. For each crossing, we identified a series of flux ropes embedded within reconnection exhausts on the sunward side of X-line. Their passage durations are <20sec, corresponding to spatial scales of a few thousands kilometers, still larger by three orders of magnitude than ion inertial length. This identification was possible particularly during intervals when PSP was closest to the HCS center. These flux ropes are distinguishable from the background exhausts by enhancements in magnetic field strength, significantly in the guide field component, travel speed slightly faster (typically by <10km/s) than surrounding outflows, and often accompanied by, though not always, increased density and reduced temperature. We attribute their origin to secondary reconnection within the exhausts and subsequent merging of smaller flux ropes into larger structures, consistent with predictions by various simulations. We suggest that such flux ropes are most readily identifiable at the HCS center where the background magnetic field is weakest so that the relative enhancement in flux rope field becomes most prominent. This observational advantage is particularly notable closer to the Sun where the high ambient magnetic field strength can otherwise obscure such structures unless the spacecraft trajectory remains within the HCS central region for a sufficient duration. Show Chinese abstract

Abstract: 理解磁通量绳与磁重联之间的关系对于空间和天体物理等离子体研究是基础性的。 在本研究中，我们报告了帕克太阳探测器（PSP）两次连续穿越日球电流片（HCS），间隔约10.5小时，在日心距离约为12个太阳半径处。 对于每次穿越，我们在X线的向日侧的重联排气中识别出一系列磁通量绳。 它们的通过时间小于20秒，对应的空间尺度为几千公里，仍然比离子惯性长度大三个数量级。 这种识别尤其在PSP最接近HCS中心的时段内成为可能。 这些磁通量绳通过磁场强度的增强，特别是引导场分量的显著增强，以及比周围流出物稍快（通常小于10公里/秒）的运动速度，以及经常伴随但并非总是伴随的密度增加和温度降低，与背景排气区分开来。 我们认为它们的起源是排气中的二次重联以及较小磁通量绳的合并形成更大的结构，这与各种模拟的预测一致。 我们认为这样的磁通量绳在HCS中心最容易被识别，因为在该处背景磁场最弱，使得磁通量绳磁场的相对增强最为明显。 这种观测优势在靠近太阳处尤为显著，因为在该处高环境磁场强度可能会掩盖这些结构，除非航天器轨迹在HCS中心区域保持足够长的时间。