PSP Observations of a Slow Shock Pair Bounding a Large‐Scale Plasmoid/Macro Magnetic Hole

Zhou, Zhecheng; Xu, Xiaokang; Zuo, Pingbing; Wang, Yi; Wang, Ludi; Ye, Yudong; Wang, Ming; Chang, Qing; Wang, Xing; Luo, Lei

doi:10.1029/2021gl097564

Cited by 2 publications

(2 citation statements)

References 46 publications

(79 reference statements)

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“…Solar wind measurements from Helios-1 at 0.31 au contain clear examples of slow shocks (Richter et al 1985;Richter & Luttrell 1987), as well as from other observatories (Chao & Olbert 1970;Burlaga & Chao 1971). More recently, PSP observed slow-mode shocks at 0.31 au (Zhou et al 2022). In situ signatures of these shocks are sharp decreases in the magnetic field accompanied by an increase in density, speed, and temperature when moving from upstream to downstream.…”

Section: Cme Coherencementioning

confidence: 99%

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Braga

Vourlidas

Liewer

et al. 2022

ApJ

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Although coronal mass ejections (CMEs) resembling flux ropes generally expand self-similarly, deformations along their fronts have been reported in observations and simulations. We present evidence of one CME becoming deformed after a period of self-similar expansion in the corona. The event was observed by multiple white-light imagers on 2021 January 20–22. The change in shape is evident in observations from the heliospheric imagers from the Wide-Field Imager for Solar Probe Plus (WISPR), which observed this CME for ∼44 hr. We reconstruct the CME using forward-fitting models. In the first hours, observations are consistent with a self-similar expansion, but later on the front flattens, forming a dimple. Our interpretation is that the CME becomes deformed at ∼0.1 au owing to differences in the background solar wind speeds. The CME expands more at higher latitudes, where the background solar wind is faster. We consider other possible causes for deformations, such as loss of coherence and slow-mode shocks. The CME deformation seems to cause a time-of-arrival error of 16 hr at ∼0.5 au. The deformation is clear only in the WISPR observations; thus, it would have been missed by 1 au coronagraphs. Such deformations may help explain the time-of-arrival errors in events where only coronagraph observations are available.

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Section: Cme Coherencementioning

confidence: 99%

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Braga

Vourlidas

Liewer

et al. 2022

ApJ

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“…This manifests as an increased proton density, increased proton temperature and as a peak in the magnetic field strength at the stream interface. The plasma discontinuity at the stream interface serves as an acceleration region (Fisk & Lee, 1980;Giacalone et al, 2002;Richardson, 2004;Yu et al, 2017) and shocks can travel in both the slower and the faster solar wind stream (Rankine, 1870;Hugoniot, 1889;Colburn & Sonett, 1966;Szabo, 2005;Zhou et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Influence of solar wind parameters on unsupervised solar wind classification with k-means

Teichmann

Heidrich-Meisner

Berger

et al. 2023

Preprint

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The properties of the solar wind represent a mixture of indicators for solar origin and transport effects. Both are of interest for the understanding of heliophysics and space weather effects. Most available solar wind classifications focus on the solar origin, in part based on transport effected properties. We aim to identify the solar wind properties that are most important for solar wind classification. We select seven solar wind properties: proton density, proton speed, proton temperature, absolute magnetic field strength, proton-proton collisional age, the ratio between the densities of O6+ and O7+ and the mean charge state of Fe. We apply an unsupervised machine learning method, k-means, to each subset of the these parameters and compare the results to a reference case based on all seven solar wind properties. Two scenarios are considered which provide a simple and a detailed solar wind classification, respectively. We identified the proton density as the most important solar wind property for solar wind classification. Furthermore, we found that charge state composition is important to accurately identify the solar source region. This holds for the simple case of three solar wind types but is even more important for a more detailed classification. In comparison to proton density and proton temperature, the solar wind speed turns out to be a less influential property. Our results underscore the importance of highly accurate measurements, in particular for proton density, proton temperature and the charge state composition.

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PSP Observations of a Slow Shock Pair Bounding a Large‐Scale Plasmoid/Macro Magnetic Hole

Cited by 2 publications

References 46 publications

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Coronal Mass Ejection Deformation at 0.1 au Observed by WISPR

Influence of solar wind parameters on unsupervised solar wind classification with k-means

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