Switchbacks in the Near-Sun Magnetic Field: Long Memory and Impact on the Turbulence Cascade

Wit, T. Dudok de; Krasnoselskikh, V.; Bale, S. D.; Bonnell, J. W.; Bowen, T. A.; Chen, Christopher H. K.; Froment, C.; Goetz, K.; Harvey, P.; Jagarlamudi, V. K.; Larosa, A.; MacDowall, R. J.; Malaspina, D.; Matthaeus, W. H.; Pulupa, M.; Velli, M.; Whittlesey, P. L.

doi:10.3847/1538-4365/ab5853

Cited by 191 publications

(156 citation statements)

References 65 publications

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“…D' Amicis et al (2019) reported that the slow solar wind with high Alfvénicity share common characteristics with the fast wind, and Perrone et al (2020) further observed that Alfvénic slow wind shows a break between the inertial range and large scales where the magnetic fluctuations saturate. It seems plausible that this −1 frequency range is related to the observations of Alfvénic switchbacks (de Wit et al 2020;Horbury et al 2020;Mozer et al 2020;McManus et al 2020), close the Sun, that provide most of the energy-containing range in the slow wind. Later on other processes such as stream interactions and reconnection could furnish the large scales and the cascade (even at lower rates).…”

Section: Discussionmentioning

confidence: 82%

Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au

Wang

et al. 2020

ApJL

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Energy supply sources for the heating process in the slow solar wind remain unknown. The Parker Solar Probe (PSP) mission provides a good opportunity to study this issue. Recently, PSP observations have found that the slow solar wind experiences stronger heating inside 0.24 au. Here for the first time we measure in the slow solar wind the radial gradient of the low-frequency breaks on the magnetic trace power spectra and evaluate the associated energy supply rate. We find that the energy supply rate is consistent with the observed perpendicular heating rate calculated based on the gradient of the magnetic moment. Based on this finding, one could explain why the slow solar wind is strongly heated inside 0.25 au but expands nearly adiabatically outside 0.25 au. This finding supports the concept that the energy added from the energy-containing range is transferred by an energy cascade process to the dissipation range, and then dissipates to heat the slow solar wind. The related issues for further study are discussed.

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Section: Discussionmentioning

confidence: 82%

Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au

Wang

et al. 2020

ApJL

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“…Since the focus of this work is the large scale solar wind structure, we first pre-process this data to remove transients and rapid fluctuations such as the newly observed δB/B ∼ 1 magnetic "switchbacks" and velocity spikes (see e.g. Bale et al (2019); Kasper et al (2019);Dudok de Wit et al (2020);Horbury et al (2020). To do this we bin the full cadence data into hourly segments, generate a histogram of the data in each bin and take the modal value (the value corresponding to the peak of the histogram).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Connectivity of the Ecliptic Plane within 0.5 au: Potential Field Source Surface Modeling of the First Parker Solar Probe Encounter

Badman

Bale

Oliveros

et al. 2020

ApJS

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We compare magnetic field measurements taken by the FIELDS instrument on Parker Solar Probe (PSP) during it's first solar encounter to predictions obtained by Potential Field Source Surface (PFSS) modeling. Ballistic propagation is used to connect the spacecraft to the source surface. Despite the simplicity of the model, our results show striking agreement with PSP's first observations of the heliospheric magnetic field from ∼0.5 AU (107.5 R ) down to 0.16 AU (35.7 R ). Further, we show the robustness of the agreement is improved both by allowing the photospheric input to the model to vary in time, and by advecting the field from PSP down to the PFSS model domain using in situ PSP/SWEAP measurements of the solar wind speed instead of assuming it to be constant with longitude and latitude. We also explore the source surface height parameter (R SS ) to the PFSS model finding that an extraordinarily low source surface height (1.3 − 1.5R ) predicts observed small scale polarity inversions which are otherwise washed out with regular modeling parameters. Finally, we extract field line traces from these models. By overlaying these on EUV images we observe magnetic connectivity to various equatorial and mid-latitude coronal holes indicating plausible magnetic footpoints and offering context for future discussions of sources of the solar wind measured by PSP.

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“…Several factors are important for a nuanced interpretation of this study's results. First, because inversions exist on a range of scales (Matteini et al 2013;Owens et al 2020;Dudok de Wit et al 2020) there is no one ideal time scale for this analysis. Thus our results here reflect the available minimum 40 s time resolution and chosen averaging times in Equations 4 and 6.…”

Section: Limitations and Caveats For Resultsmentioning

confidence: 99%

“…PSP found magnetic inversions to be ubiquitous in the inner (down to 0.16 AU) heliosphere. These inversion durations range from some seconds to hours (Dudok de Wit et al 2020). The change in the field orientation is matched with an oppositely-directed spike in the bulk velocity (Bale et al 2019;Kasper et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Evolving solar wind flow properties of magnetic inversions observed by Helios

Macneil

Owens

Wicks

et al. 2020

Monthly Notices of the Royal Astronomical Society

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In its first encounter at solar distances as close as r = 0.16 au, Parker Solar Probe observed numerous local reversals, or inversions, in the heliospheric magnetic field (HMF), which were accompanied by large spikes in solar wind speed. Both solar and in situ mechanisms have been suggested to explain the existence of HMF inversions in general. Previous work using Helios 1, covering 0.3–1 au, observed inverted HMF to become more common with increasing r, suggesting that some heliospheric driving process creates or amplifies inversions. This study expands upon these findings, by analysing inversion-associated changes in plasma properties for the same large data set, facilitated by observations of ‘strahl’ electrons to identify the unperturbed magnetic polarity. We find that many inversions exhibit anticorrelated field and velocity perturbations, and are thus characteristically Alfvénic, but many also depart strongly from this relationship over an apparent continuum of properties. Inversions depart further from the ‘ideal’ Alfvénic case with increasing r, as more energy is partitioned in the field, rather than the plasma, component of the perturbation. This departure is greatest for inversions with larger density and magnetic field strength changes, and characteristic slow solar wind properties. We find no evidence that inversions that stray further from ‘ideal’ Alfvénicity have different generation processes from those which are more Alfvénic. Instead, different inversion properties could be imprinted based on transport or formation within different solar wind streams.

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Switchbacks in the Near-Sun Magnetic Field: Long Memory and Impact on the Turbulence Cascade

Cited by 191 publications

References 65 publications

Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au

Energy Supply for Heating the Slow Solar Wind Observed by Parker Solar Probe between 0.17 and 0.7 au

Magnetic Connectivity of the Ecliptic Plane within 0.5 au: Potential Field Source Surface Modeling of the First Parker Solar Probe Encounter

Evolving solar wind flow properties of magnetic inversions observed by Helios

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