The S-Web Origin of Composition Enhancement in the Slow-to-moderate Speed Solar Wind

Lynch, B. J.; Viall, N. M.; Higginson, A. K.; Zhao, L.; Lepri, S. T.; Sun, Xudong

doi:10.3847/1538-4357/acc38c

Cited by 5 publications

(3 citation statements)

References 168 publications

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“…We note that the signatures of elevated helium abundances appear before the HCS crossing and not explicitly during the crossing, suggesting outflowing plasma at the edge of the streamer is enriched in helium and not specifically the current sheet itself, as has been reported in other studies (Rivera et al 2021;Lynch et al 2023).…”

Section: Solar Windsupporting

confidence: 75%

“…The various heavy-ion features that remain imprinted in the plasma once it leaves the corona provide insight to processes active in the corona. Therefore, the ion and elemental composition measured throughout the heliosphere are important tracers of the eruption processes (Lynch et al 2011;Rakowski et al 2011;Laming et al 2023;Rivera et al 2023), solar-wind release and dynamic outflow (Landi et al 2012b;Scott et al 2022), and properties of the plasma's source region (Xu & Borovsky 2015;Zurbuchen et al 2016;Ervin et al 2023;Lynch et al 2023).…”

Section: Introductionmentioning

confidence: 99%

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Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14

Johnson,

Rivera,

Niembro

et al. 2024

ApJ

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Parker Solar Probe is a mission designed to explore the properties of the solar wind closer than ever before. Detailed particle observations from the Solar Probe Cup (SPC) have primarily focused on examining the proton population in the solar wind. However, several periods throughout the Parker mission have indicated that SPC has observed a pronounced and distinctive population of fully ionized helium, He2+. Minor ions are imprinted with properties of the solar wind’s source region, as well as mechanisms active during outflow, making them sensitive markers of its origin and formation at the Sun. Through a detailed analysis of the He2+ velocity distributions functions, this work examines periods where significant and persistent He2+ peaks are observed with SPC. We compute the helium abundance and examine the stream’s bulk speed, density, temperature, magnetic field topology, and electron strahl properties to identify distinctive solar-wind features that can provide insight to their solar source. We find that nearly all periods exhibit an elevated mean helium composition (8.34%) compared to typical solar wind and a majority (∼87%) of these periods are connected to coronal mass ejections (CMEs), with the highest abundance reaching 23.1%. The helium abundance and number of events increases as the solar cycle approaches maximum, with a weak dependence on speed. Additionally, the events not associated with a CME are clustered near the heliospheric current sheet, suggesting they are connected to streamer belt outflows. However, there are currently no theoretical explanations that fully describe the range of depleted and elevated helium abundances observed.

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Section: Solar Windsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14

Johnson,

Rivera,

Niembro

et al. 2024

ApJ

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“…The origins and properties of the slow solar wind, however, are much more diverse. Suggested sources of slow wind include active regions (e.g., Sakao et al 2007;Edwards et al 2016;Harra et al 2023), helmet streamers and pseudostreamers (e.g., Wang et al 2000;Antiochos et al 2011;Lynch et al 2023), and coronal hole boundaries (e.g., Wang & Sheeley 1990;Wang et al 2000;Antonucci et al 2005;Woolley et al 2021). The exact nature of the slow solar wind is still under debate due to various complexities.…”

Section: Introductionmentioning

confidence: 99%

Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements

Jiao,

Liu,

Ran

et al. 2023

ApJ

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We identify more than 10 steady sub-Alfvénic solar wind intervals from the measurements of the Parker Solar Probe (PSP) from encounter 8 to encounter 14. An analysis of these sub-Alfvénic intervals reveals similar properties and similar origins. In situ measurements show that these intervals feature a decreased radial Alfvén Mach number resulting from a reduced density and a relatively low velocity, and that switchbacks are suppressed in these intervals. Magnetic source tracing indicates that these sub-Alfvénic streams generally originate from the boundaries inside coronal holes or narrow/small regions of open magnetic fields. Such properties and origins suggest that these streams are mostly low Mach-number boundary layers (LMBLs), which is a special component of the pristine solar wind proposed by Liu et al. We find that the LMBL wind, the fast wind from deep inside coronal holes, and the slow streamer wind constitute three typical components of the young solar wind near the Sun. In these sub-Alfvénic intervals, the Alfvén radius varies between 15 and 25 solar radii, in contrast with a typical 12 radii for the Alfvén radius of the super-Alfvénic wind. These results give a self-consistent picture interpreting the PSP measurements in the vicinity of the Sun.

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Modeling a Coronal Mass Ejection from an Extended Filament Channel. II. Interplanetary Propagation to 1 au

Palmerio,

Maharana,

Lynch

et al. 2023

ApJ

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We present observations and modeling results of the propagation and impact at Earth of a high-latitude, extended filament channel eruption that commenced on 2015 July 9. The coronal mass ejection (CME) that resulted from the filament eruption was associated with a moderate disturbance at Earth. This event could be classified as a so-called “problem storm” because it lacked the usual solar signatures that are characteristic of large, energetic, Earth-directed CMEs that often result in significant geoeffective impacts. We use solar observations to constrain the initial parameters and therefore to model the propagation of the 2015 July 9 eruption from the solar corona up to Earth using 3D magnetohydrodynamic heliospheric simulations with three different configurations of the modeled CME. We find the best match between observed and modeled arrival at Earth for the simulation run that features a toroidal flux rope structure of the CME ejecta, but caution that different approaches may be more or less useful depending on the CME–observer geometry when evaluating the space weather impact of eruptions that are extreme in terms of their large size and high degree of asymmetry. We discuss our results in the context of both advancing our understanding of the physics of CME evolution and future improvements to space weather forecasting.

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The S-Web Origin of Composition Enhancement in the Slow-to-moderate Speed Solar Wind

Cited by 5 publications

References 168 publications

Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14

Helium Abundance Periods Observed by the Solar Probe Cup on Parker Solar Probe: Encounters 1–14

Properties of Steady Sub-Alfvénic Solar Wind in Comparison with Super-Alfvénic Wind from Parker Solar Probe Measurements

Modeling a Coronal Mass Ejection from an Extended Filament Channel. II. Interplanetary Propagation to 1 au

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