Magnetic Reconnection in the Heliospheric Current Sheet Embedded in an Interplanetary Coronal Mass Ejection Sheath

Abstract Solar wind conditions in the heliosphere are altered by solar wind transients such as shocks and interplanetary coronal mass ejections (ICMEs). The interactions of coherent solar wind structures such as the heliospheric current sheet (HCS) with the transients remain incompletely understood, however. Here, we report the first in situ spacecraft observations showing two magnetic reconnection exhausts in the HCS embedded in the sheath region of an ICME. The dropout (presence) of strahl electrons indicates the disconnection (connection) of an exhaust region from (to) Sun. We perform a multispacecraft analysis, which shows that reconnection in the HCS embedded in an ICME sheath can operate in a quasi-steady manner at 1 au, with the observations across the outflow regions showing a good correlation with the Walén relation. The two reconnecting HCS crossings in the ICME sheath are compared to two other HCS crossings, one in the sheath and one in the solar wind upstream of the ICME shock, which show no magnetic reconnection signatures. These results highlight interplanetary transients as space plasma environments that can host dynamics infrequently observed in the solar wind at Earth’s orbit.