A review of heliospheric plasma sheets and their impacts on planetary space weather

The heliospheric plasma sheet (HPS) is generally viewed as a structure straddling a heliospheric current sheet (HCS) where the interplanetary magnetic field changes polarity. It is generally characterized by enhanced density, depressed magnetic field and enhanced plasma β. The HPSs are important drivers of the interplanetary disturbances and planetary space weather, and have received extensive attention in the literature. The HPSs are possibly filled with current sheets, waves, and magnetic islands, which are receiving much more attentions recently. In this brief review, we introduce the research progress of the HPSs, with focus on their sources, formation mechanisms, properties based on in-situ observations, as well as the potential impacts on planetary space weather. Also, we try to discuss some points that are still under debate and remain elusive.