In Situ Analysis of Heliospheric Current Sheet Propagation

Peng, Jinfang; Liu, Yong C.‐M.; Huang, Jia; Li, Hui; Klecker, B.; Galvin, A. B.; Simunac, K. D. C.; Farrugia, Charles J.; Jian, L. K.; Liu, Yang; Zhang, Jie

doi:10.1002/2017ja024194

Cited by 6 publications

(11 citation statements)

References 57 publications

(70 reference statements)

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“…Although the orientations generally match the direction expected from the HCS, they are much steeper. Burton et al 1994;Peng et al 2017). Unlike these studies, we measured the local orientation to be steeper than the relatively flat HCS seen with in situ observations and the PFSS model.…”

Section: Hcs Structurementioning

confidence: 86%

“…Despite its simplicity, PFSS models have been shown to compare well with more sophisticated numerical models (Riley et al 2006), as well as in situ measurements at 1 AU (Jian et al 2015) and closer to the Sun (Badman et al 2020;Panasenco et al 2020). The local inclination of the HCS predicted by the PFSS model has also been shown to be consistent with in situ measurements except in those cases where transients, such as coronal mass ejections (CMEs), are present (Klein & Burlaga 1980;Burton et al 1994;Peng et al 2017). In situ manifestations of CMEs are commonly observed around HCS crossings where it has been argued that they carry the sector boundary, rather than being structures that drape or push the HCS aside (Gosling et al 1987a;Crooker et al 1993;Crooker & Intriligator 1996;Forsyth et al 1997).…”

Section: Introductionmentioning

confidence: 89%

“…At solar minimum, when the Sun's magnetic field can be well described by a dipole configuration, the HCS has a limited latitudinal extent, due to its relation to the tips of closed field lines in the equatorial streamer belt (Gosling et al 1981;Hoeksema et al 1983). The HCS also exhibits a low local inclination, meaning that all parts of the HCS are relatively parallel with the solar equator (Smith & Thomas 1986;Peng et al 2017). Therefore, at solar minimum the HCS is generally flat with a well defined shape that can persist for several solar rotations (Thomas & Smith 1981;Riley et al 2002).…”

Section: Introductionmentioning

confidence: 99%

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Multi-spacecraft Study of the Solar Wind at Solar Minimum: Dependence on Latitude and Transient Outflows

Laker,

Horbury,

Bale

et al. 2021

Preprint

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Context. The recent launches of Parker Solar Probe (PSP), Solar Orbiter (SO) and BepiColombo, along with several older spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously. Aims. We take advantage of this unique spacecraft constellation, along with low solar activity across two solar rotations between May and July 2020, to investigate how the Heliospheric Current Sheet (HCS) structure varies with latitude. Methods. We visualise the sector structure of the inner heliosphere by ballistically mapping the polarity and solar wind speed from several spacecraft onto the Sun's source surface. We compare this observed sector structure, and the local orientations of the boundaries, to a predicted HCS. Results. We show that fine scale ripples in the HCS can be resolved down to several degrees in longitude, with solar wind speed being a useful indicator of when a spacecraft is near the HCS without changing magnetic polarity. We found that the local orientation of sector boundaries were broadly consistent with the shape of the HCS but were steepened due to compression from stream interaction regions. We identified several transient magnetic clouds associated with HCS crossings, and have shown that these could disrupt the local HCS orientation up to five days after their passage, but did not significantly affect the position of the HCS. Conclusions. This spacecraft constellation, along with ballistic mapping, can reveal the structure of the HCS on scales of a few degrees in longitude and latitude, while discerning between co-rotating and transient structures. This also provides an accurate representation of the solar wind within ±10 • latitude, which could be used as a more rigorous constraint on solar wind models and future space weather predictions. In the future, this range of latitudes will increase as SO's orbit becomes more inclined.

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Section: Hcs Structurementioning

confidence: 86%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Multi-spacecraft Study of the Solar Wind at Solar Minimum: Dependence on Latitude and Transient Outflows

Laker,

Horbury,

Bale

et al. 2021

Preprint

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“…SFRs in the vicinity of HCSs only show type B and type D distributions. Solar wind in the vicinity of HCSs is generally slow speed (e.g., Y. Liu et al, ; Peng et al, ), which generally shows low Q <Fe> (Abbo et al, ; Lepri et al, ). As the charge states of heavy ions are frozen‐in below a few solar radii, Q <Fe> is not expected to be changing in the interplanetary medium.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2018

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Small flux ropes (SFRs) have been studied for decades, but their source regions and formation mechanisms are still under debate. In this study, we focus on the formation mechanism of the twisted structures of SFRs. Current research on magnetic clouds suggests five‐type distributions of the time structure of iron average charge states (Q), which imply different formation mechanisms of twisted structures. We use a similar method to identify the Q types of 25 SFRs. However, only four of these five types of distributions are found among these SFRs. Because different origins of SFRs are characteristically affecting the formation of Q types, the possible source regions of these SFRs are distinguished. With additional compositional parameters, SFRs are reconfirmed to originate from two types of source regions: the solar corona and the interplanetary medium. Based on these results, our analysis indicates that the twisted structures of SFRs originating from the solar corona may be formed predominately during eruptions. SFRs originating from interplanetary space are related to complex magnetic reconnection processes, which may result in intricate Q distributions due to the reconstruction of magnetic field topology.

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“…We select seven HCSs observed by all three spacecraft from the list of 35 HCSs identified by Peng et al (2017) The same HCS sweeps ACE and the twin STEREO spacecraft at different times. In order to study the global shape of the HCS, we need to shift the measurements to one time using the solar wind speed.…”

Section: Event Selectionmentioning

confidence: 99%

The Warped Heliospheric Current Sheet

et al. 2019

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The global shape of the intersection of the heliospheric current sheet (HCS) with the heliospheric equatorial plane is usually considered to be an Archimedean spiral, however, so far this has not been measured directly. We used multi-spacecraft measurements to determine its global shape. The time-shifted measured locations are fitted with Archimedean spirals. In most cases, the locations are fitted very well with Archimedean spirals, in addition to the direction of HCS determined by the Minimum Variation Analysis. However, there is one case in which the direction of the HCS does not fit well with the Archimedean spiral and therefore we fit it with a sinusoidal function in addition to an Archimedean spiral. The result showed that in some cases, the HCS is better described with an Archimedean spiral, superposed by small-scale ripples.

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In Situ Analysis of Heliospheric Current Sheet Propagation

Cited by 6 publications

References 57 publications

Multi-spacecraft Study of the Solar Wind at Solar Minimum: Dependence on Latitude and Transient Outflows

Multi-spacecraft Study of the Solar Wind at Solar Minimum: Dependence on Latitude and Transient Outflows

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

The Warped Heliospheric Current Sheet

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