Occurrence and Evolution of Switchbacks in the Inner Heliosphere: Parker Solar Probe Observations

Abstract

Since its launch in 2018, the Parker Solar Probe (PSP) mission revealed the presence of numerous fascinating phenomena occurring closer to the Sun, such as the presence of ubiquitous switchbacks (SBs). The SBs are large magnetic field deflections of the local magnetic field relative to a background field. We investigated the statistical properties of the SBs during the first 10 encounters between 13.28 and 58 solar radii (R ⊙) using data from the SWEAP and FIELDS suites on board PSP. We find that the occurrence percentage of small deflections with respect to the Parker spiral decreases with radial distance (R). In contrast, the occurrence percentage of the large deflections (SBs) increases with R, as does the SB patches. We also find that the occurrence of SBs correlates with the bulk velocity of the solar wind, i.e., the higher the solar wind velocity, the higher the SB occurrence. For V sw ≤ 400 km s−1, the SB occurrence percentage shows a constantly increasing trend between 13 and 58 R ⊙. However, for V sw > 400 km s−1, the occurrence percentage saturates beyond 35 R ⊙. The occurrence percentage of mini SB patches (<60 s) shows a decreasing trend with R, while the occurrence percentage of long-duration SB patches (>200 s) increases with R. Sub-Alfvénic regions that we analyzed during Encounters 8–10 have not shown any SBs. This analysis of the PSP data hints that some of the SBs are decaying and some are being created in situ.

A Closer Look at Small-scale Magnetic Flux Ropes in the Solar Wind at 1 au: Results from Improved Automated Detection

“…Interestingly, as we have found to be the case with SMFRs, SB occurrence is correlated with bulk velocity (Mozer et al 2021;Jagarlamudi et al 2023). We have shown that the occurrence of SMFRs is correlated with the average bulk velocity as a consequence of a nearly constant radial density (combined with a slightly higher radial density in faster solar wind types).…”

Series of Small-scale Low Plasma β Magnetic Flux Ropes Originating from the Same Longitudinal Region: Parker Solar Probe Observations

“…At present, it is unclear to us specifically how our successive SMFR observations relate to the findings in all these previous reports on the relation between flux ropes and switchbacks. Nevertheless, we note that one difference lies in the timescale of the flux ropes, which is ∼0.5 hr or longer in our SMFRs, which is much longer than those for flux ropes and switchbacks considered in previous works (Drake et al 2021;Agapitov et al 2022) although the recent work by Jagarlamudi et al (2023) included long-duration switchbacks measured by the PSP. Further in-depth work on how our SMFR observations link to all these issues is desired.…”

Properties of an Interplanetary Shock Observed at 0.07 and 0.7 au by Parker Solar Probe and Solar Orbiter

“…At PSP, upstream of the shock, the magnetic field is mostly radial and interspersed with one-sided Alfvénic fluctuations (Gosling et al 2009) of the magnetic field and ion bulk velocity, known as magnetic switchbacks, with moderate-amplitude angular deflections in the magnetic field, as expected for very low heliocentric distances (e.g., Jagarlamudi et al 2023). SBs are a crucial feature of the solar wind in the inner heliosphere, as extensively shown in previous literature (Dudok de Wit et al 2020;Krasnoselskikh et al 2020;Larosa et al 2021;Liang et al 2021;Pecora et al 2022;Jagarlamudi et al 2023;Liu et al 2023;Raouafi et al 2023). Here, we have the opportunity to study how such structures are processed by shock waves, a crucial point of this work summarized in Section 3.2.…”