A multievent study of the coincidence of heliospheric current sheet and stream interface

Abstract

Generally, the heliospheric current sheet (HCS) is separated from the stream interface (SI) at about 1 AU. A recent study found an event where the HCS coincides with the SI, and in which the HCS is separated from the true sector boundary (TSB), defined by the switch of suprathermal electron pitch angle distributions. We present a multievent study by using STEREO, ACE, and Wind data during 2007 to 2010 to investigate whether other classes of such coincidence cases exist, as well as their stability. We find coincidence cases related to ideal HCSs, separated TSB and HCS, or heat flux dropouts in the vicinity; therefore, we define them as types I, II, and III. Among the nine coincidence cases, there are seven type I, one type II, and one type III. For each type, a possible schematic origin is presented. We also compared the observations on different spacecraft. Only two out of nine cases are observed by several spacecraft with a large separation, indicating that the coincidence structures are usually unstable. The study also shows that the coincidence cases have a variable connection with pseudostreamers. Interchange reconnection and pseudostreamers could play a role in forming these coincidence cases and lead to different configurations in different situations.

In Situ Analysis of Heliospheric Current Sheet Propagation

“…The stream interface (SI) is the boundary between the slow and fast solar wind (Burlaga, ; Gosling et al, ). Sometimes, the HCSs are found within a few hours from the SI, and they may even coincide with each other as recent studies showed (Huang, Liu, & Klecker et al, ; Huang, Liu, & Qi et al, ). The evolution of stream interfaces was studied by Simunac et al () who concluded that in addition to radial and longitudinal separation between two spacecraft, the latitudinal separation and source evolution are also important for determining the propagation time between two spacecraft.…”

“…These five types, are shown in Figure , reproduced from Owens et al (). In general, type (a) and type (c) HCS are considered as ideal HCSs implying that there are no rolling back magnetic field lines and HCS coincides with the TSB (Huang, Liu, & Qi et al, ; Liu et al, ; Owens et al, ). Types (b), (d), and (e) are nonideal, because the HCS is separated from the TSB or even no TSB is observed.…”

“…HCS other as recent studies showed Huang, Liu, & Qi et al, 2016). The evolution of stream interfaces was studied by Simunac et al (2009) who concluded that in addition to radial and longitudinal separation between two spacecraft, the latitudinal separation and source evolution are also important for determining the propagation time between two spacecraft.…”

The Distributions of Iron Average Charge States in Small Flux Ropes in Interplanetary Space: Clues to Their Twisted Structures

“…In addition, nearly 90% of the SFRs that appear far away from HCSs have counterstreaming suprathermal electrons (CSEs), but those adjacent to HCSs do not always show CSEs (Feng et al, ). The CSEs reveal that the suprathermal electrons stream along the magnetic field, both in parallel and antiparallel directions, implying closed magnetic field lines (e.g., Huang, Liu, Qi, et al, ; Lavraud et al, ). Therefore, we suggest that the SFRs originating from HCSs should satisfy the following criteria: a HCS in the vicinity, no CSEs, and N α / N p is smaller than 0.06 but larger than 0.02.…”

A multispacecraft study of a small flux rope entrained by rolling back magnetic field lines

“…Although some scientists explain the separation with magnetic islands [Khabarova et al, 2015[Khabarova et al, , 2016, it is generally accepted that the mismatch is caused by rolling back magnetic field lines [e.g., Kahler et al, 1996;Crooker et al, 2004;Foullon et al, 2009]. Several studies also find that the rolling back magnetic field lines are closely related to interchange reconnection processes, which could occur at the streamer belt [Wang et al, 2000;Crooker et al, 2004], at pseudostreamers [Owens et al, 2013], or between them [Huang et al, 2016a[Huang et al, , 2016b.…”