Oblique Compressible Waves in the Reconnection Exhaust Region Embedded in the Inner Heliospheric Current Sheet Observed by Parker Solar Probe

Abstract

Magnetic reconnection is an important physical process of energy conversion in the heliosphere. Parker Solar Probe (PSP) passes through current sheets of the inner heliosphere and is likely to encounter magnetic reconnection events there. PSP traversed a magnetic reconnection exhaust region that occurred in the coronal streamer during its perihelion Encounter 8. We report an observation of the counterstream of strahl electrons and compressible waves in the exhaust region on the antisunward side of the reconnection site. We analyze the wave characteristics using electromagnetic singular value decomposition techniques and find that the propagation direction of the compressible waves is quasi-perpendicular to the local magnetic field. Combining with the topology of the magnetic field, we infer that the compressible waves converge from the edge to the center of the exhaust region, and then propagate away from it. Further, we select 12 magnetic reconnection events during Encounter 5–8 for statistics and find that the oblique compressible waves are commonly detected throughout the inner heliospheric current sheet. In addition, we discuss the possible nature of wave branches for these compressible waves. Our work shows that magnetic reconnection in the heliosphere not only changes the topology of the large-scale magnetic field in the heliosphere, but also affects the transport characteristics of solar wind plasma and suprathermal particles, and regulates the states of waves and turbulence in the heliosphere.