Large-density (>50 cm−3) heliospheric plasma sheets recorded by the Wind spacecraft between 1995 and 2017

Abstract

A survey of previous studies of the heliospheric plasma sheet (HPS) suggests a bimodal distribution for the occurrence of the HPS peak plasma density. While the majority of HPS events have a peak density smaller than ∼30 cm−3, there is evidence that large density (>50 cm−3) HPS events can exist. A bimodal distribution would suggest a two-source scenario for the HPS observed at 1 AU. In this study we focus on large density HPS events. We survey the solar wind data acquired from the Wind spacecraft between 1995 and 2017 and identify 108 large-density HPS events with a distribution peak at 55 cm−3, confirming the bimodal distribution. We also find that 80 (74%) of these large-density HPS events are associated with interplanetary shocks. The yearly occurrence of these large-density HPS events nearly follows the yearly occurrence of interplanetary shock. This result suggests that large-density HPS events are likely caused by compression of interplanetary shocks within 1 AU.